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Climate change,forests andforest management

An overview

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Climate change, forests and forest management

An overview

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Food and

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Climate change,forests andforest management

An overview

byWilliam M. CieslaForest Protection OfficerFAO Forest Resources Division

I on La Digue be particularly ;limate change, md intensity of

Climate change, forests and forest management

An overview

by William M. Ciesla Forest Protection Officer FAO Forest Resources Division

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The designations employed and the presentation of material in thispublication do not imply the expression of any opinion whatsoeveron the part of the Food and Agriculture Organization of the UnitedNations conceming the legal status of any country, territory, city orarea or of its authorities, or conceming the delimitation of itsfrontiers or boundaries.

M-08ISBN 92-5-103664-0

All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means, electronic,mechanical, photocopying or otherwise, without the prior permission of thecopyright owner. Applications for such permission, with a statement of thepurpose and extent of the reproduction, should be addressed to the Director,Publications Division, Food and Agdculture Organization of the United Nations,Viale dells Terme di Caracalla, 00100 Rome, Italy.

0 FAO 1995

The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

M-08 ISBN 92-5-103664-0

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, me.chanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome,ltaly.

© FAO 1995

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FOREWORD

Changes in the world's climate, due to increases in theconcentration of carbon dioxide and other greenhouse gases in theEarth's atmosphere, have the potential to significantly affect forestsand the practice of forestry. The probability of climate change isone of today's leading environmental concerns. The issue iscomplex and filled with uncertainties. Information available on thesubject is often confusing and conflicting.

Climate is the key factor which determines the distribution ofvegetation. The relation of climate change to the conservation anddevelopment of the world's forests is therefore, an important issueto consider. Forests can contribute to the greenhouse effect, theycan also be affected by climate change and they offer opportunitiesto mitigate its effects.

It is important for foresters to have an understanding of the climatechange issue and its implications. This document, which ispresented in question and answer format, is designed to serve as ageneral reference on the subject of climate change and forests. Theanswers are based on the current world's literature including themost recent analyses by the Intergovernmental Panel on ClimateChange (IPCC). It is hoped that forest planners and managers willfind it useful in the preparation and implementation of theirprogrammes and in providing advice to decision makers.

J. P. Lanly, DirectorForest Resources Division

Forestry Department

I

FOREWORD

Changes in the world's climate, due to increases in the concentration of carbon dioxide and other greenhouse gases in the Earth's atmosphere, have the potential to significantly affect forests and the practice of forestry. The probability of climate change is one of today's leading environmental concerns. The issue is complex and filled with uncertainties. Information available on the subject is often confusing and conflicting.

Climate is the key factor which determines the distribution of vegetation . The relation of climate change to the conservation and development of the world ' s forests is therefore, an important issue to consider. Forests can contribute to the greenhouse effect, they can also be affected by. climate change and they offer opportunities to mitigate its effects.

It is important for foresters to have an understanding of the climate change issue and its implications . This document, w hich is presented in Question and answer format, is designed to serve as a general reference on the subject of climate change and forests. The answers are based on the current world's literature including the most recent analyses by the Intergovernmental Panel on Climate Change OPCC) . It is hoped that forest planners and managers will find it useful in the preparation and implementation of their programmes and in providing advice to decision makers.

J . P. Lanly, Director Forest Resources Division

Forestry Department

ACKNOWLEDGMENTS

The helpful and constructive comments provided by a large numberof people who reviewed this document is gratefully acknowledged.

External reviews were kindly provided by M. Fosberg, USDA ForestService, Washington DC, S. Brown, US EPA, Corvalis, Oregon, USAand M. Hosny El Lakany, Desert Development Center, AmericanUniversity, Cairo, Egypt.

Internal (FAO) reviews were provided by W.G. Sombroek, Director,Lands and Water Development Division and Chairman,Interdepartmental Working Group on Climate Change; R. Gommes,Coordinator, Agrometeorology Group, Remote Sensing Centre; J.P.Lanly, Director, Forest Resources Division; C. Palmberg-Lerche,Chief, Forest Resources Development Service; J. Ball, Senior ForestPlantations Officer, S. Braatz, Agroforestry and Land Use Officer; P.Vantomme, Forest Management Officer; D. Dykstra, ForestHarvesting Officer (Presently with CIFOR, Bogor, Indonesia); M.Trossero, Wood Based Energy Officer; C. Chandrasekharan, Non-Wood Forest Products Officer and D. Suparmo, Advisor, TropicalForests Action Programme.

Special thanks are given to J.B. Harrington, formerly of thePetawawa National Forestry Institute, Ontario, Canada, for hisassistance with the technical editing of the manuscript and F. Monti,FAO, Forestry Department Librarian, who assisted in accessing themassive literature available on climate change.

ii

ACKNOWLEDGMENTS

The helpful and constructive comments provided by a large number of people who reviewed this document is gratefully acknowledged.

External reviews were kindly provided by M. Fosberg, USDA Forest Service, Washington DC, S. Brown, US EPA, Corvalis, Oregon, USA and M. Hosny El Lakany, Desert Development Center, American University, Cairo, Egypt.

Internal (FAO) reviews were provided by W.G. Sombroek, Director, Lands and Water Development Division and Chairman, Interdepartmental Working Group on Climate Change; R. Gommes, Coordinator, Agrometeorology Group, Remote Sensing Centre; J.P. Lanly, Director, Forest Resources Division; C. Palmberg-Lerche, Chief, Forest Resources Development Service; J. Ball, Senior Forest Plantations Officer, S. Braatz, Agroforestry and Land Use Officer; P. Vantomme, Forest Management Officer; D. Dykstra, Forest Harvesting Officer (Presently with CIFOR, Bogor, Indonesia); M. Trossero, Wood Based Energy Officer; C. Chandrasekharan, NonWood Forest Products Officer and D. Suparmo, Advisor, Tropical Forests Action Programme.

Special thanks are given to J.B. Harrington, formerly of the Petawawa National Forestry Institute, Ontario, Canada, for his assistance with the technical editing of the manuscript and F. Monti, FAO, Forestry Department Librarian, who assisted in accessing the massive literature available on climate change.

TABLE OF CONTENTS

FOREWORD

ACKNOWLEDGEMENTS

TABLE OF CONTENTS

LIST OF ACRONYMS ix

LIST OF TABLES xii

LIST OF BOXES xiii

LIST OF FIGURES xiv

INTRODUCTION 1

CHAPTER 1 - THE EARTH'S CLIMATE - A DYNAMIC ENTITY 4

HOW ARE WEATHER AND CLIMA TE DEFINED? 4

TO WHAT EXTENT HAS THE EARTH'S CLIMA TE CHANGEDDURING THE COURSE OF GEOLOGIC HISTORY? 4

WHAT CHA NGES HA VE OCCURRED IN THE EARTH'SCLIMA TE SINCE THE BEGINNING OF RECORDED HUMANHISTORY? 5

WHAT FACTORS CAN CAUSE CHANGES IN THE EARTH'SCLIMA TE? 9

CHAPTER 2 - THE GREENHOUSE EFFECT 1 5

5. WHAT IS THE "GREENHOUSE EFFECT" AND HOW DOES ITINFLUENCE THE EARTH'S CLIMA TE? 15

iii

TABLE OF CONTENTS

FOREWORD ....... . ... . . .• ..•.. •.. ......•....... i

ACKNOWLEDGEMENTS ....•............. . ........ ii

TABLE OF CONTENTS ..•............•..•.....•.. iii

LIST OF ACRONYMS ..... . ... . ..•....... . ........ ix

LIST OF TABLES .. . ... •........ •... • . .• . ....•... xii

LIST OF BOXES . . . . . . • . . . • . . . . . . . . . . . . • . . . . . • .. xiii

LIST OF FIGURES .........•..•..•........... . .. . xiv

INTRODUCTION . . . . . . . • . . . . . • . . • . . . . . . . . . • . . . . . . 1

CHAPTER 1 - THE EARTH'S CLIMATE - A DYNAMIC ENTITY 4

1. HOW ARE WEA THER AND CLlMA TE DEFINED? .... . 4

2. TO WHA T EXTENT HAS THE EARTH'S CLlMA TE CHANGED DURING THE COURSE OF GEOLOGIC HISTORY? . . . .. 4

3. WHA T CHANGES HA VE OCCURRED IN THE EARTH'S CLlMA TE SINCE THE BEGINNING OF RECORDED HUMAN HISTORY? .................. . .... .. ...... 5

4. WHAT FACTORS CAN CAUSE CHANGES IN THE EARTH'S CLIMATE? ........................ . . . .... 9

CHAPTER 2 - THE GREENHOUSE EFFECT . . . . . . . . . . . .. 15

5. WHA T IS THE "GREENHOUSE EFFECT" AND HOW DOES IT INFLUENCE THE EARTH'S CLlMA TE? . ......... . 15

iv

WHICH GASES ARE CONSIDERED TO BE GHGS AND WHATARE THE SOURCES OF THESE GASES? 18

WHAT IS THE SIGNIFICANCE OF HUMAN SOURCES OFGHGS? 22

DO ALL GHGS HA VE AN EQUAL WARMING EFFECT? 22

WHAT EVIDENCE EXISTS TO SUPPORT THE IDEA THATGHG LEVELS IN THE ATMOSPHERE ARE INCREASING? 23

WHICH COUNTRIES PRESENTLY MAKE THE GREA TESTCONTRIBUTION TO ELEVA TED LEVELS OF GHGS? .. 25

HOW CAN AEROSOLS COUNTERACT THE EFFECTS OFGHGS 25

CHAPTER 3 - PREDICTED CHANGES IN THE EARTH'SCLIMATE AND EXPECTED EFFECTS 27

IN GENERAL, WHAT ARE THE PREDICTED EFFECTS OFINCREASED LEVELS OF GHGS ON THE EARTH'SCLIMATE? 27

HOW ARE CHANGES IN THE EARTH'S CL/MATEPREDICTED? 27

HOW RELIABLE ARE PRESENT PREDICTIONS OF CLIMA TECHANGE? 30

WHAT CHA NGES IN CLIMA TE ARE PREDICTED WITH ADOUBLING OF CO, FROM PRE-INDUSTRIAL REVOLUTIONLEVELS? 31

IS THE CLIMA TE OF SOME REGIONS OF THE WORLDEXPECTED TO CHA NGE TO A CREA TER DEGREE THANOTHERS? 33

iv

6. WHICH GASES ARE CONSIDERED TO BE GHGS AND WHA T ARE THE SOURCES OF THESE GASES? . . . . . . . . .. 18

7. WHA T IS THE SIGNIFICANCE OF HUMAN SOURCES OF GHGS? ...... .. . . ..... : ........... . .... 22

B. DO ALL GHGS HA VE AN EQUAL WARMING EFFECT? 22

9. WHA T EVIDENCE EXISTS TO SUPPORT THE IDEA THA T GHG LEVELS IN THE A TMOSPHERE ARE INCREASING? 23

10. WHICH COUNTRIES PRESENTLY MAKE THE GREATEST CONTRIBUTION TO ELEVA TED LEVELS OF GHGS? . . 25

11 . HOW CAN AEROSOLS COUNTERACT THE EFFECTS OF GHGS ... .. . . . . . .. . . .. . .... . .......... . 25

CHAPTER 3 - PREDICTED CHANGES IN THE EARTH'S CLIMATE AND EXPECTED EFFECTS . . . ... . . . ... 27

12. IN GENERAL, WHAT ARE THE PREDICTED EFFECTS OF INCREASED LEVELS OF GHGS ON THE EARTH'S CLlMA TE? ..... . .... . .. . ...... . ....... .. 27

13. HOW ARE CHANGES IN THE EARTH'S CLIMATE PREDICTED? . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27

14. HOW RELIABLE ARE PRESENT PREDICTIONS OF CLlMA TE CHANGE? .......... . .. . ........ ..... .. . 30

15. WHAT CHANGES IN CLIMATE ARE PREDICTED WITH A DOUBLING OF CO2 FROM PRE-INDUSTRIAL REVOLUTION LEVELS? .... .. ................... ...... 31

16. IS THE CLlMA TE OF SOME REGIONS OF THE WORLD EXPECTED TO CHANGE TO A GREA TER DEGREE THAN OTHERS? ............................... 33

WHAT CHA NGES IN THE LEVEL OF THE OCEANS AREEXPECTED DUE TO CLIMA TE CHANGE? 34

HOW WILL PLANTS, INCLUDING TREES, BE INFLUENCEDBY CHANGES IN THE LEVELS OF GHGs IN THE EARTH'SATMOSPHERE AND RESULTANT CHANGES INTEMPERA TURE AND PRECIPITATION ? 34

HOW MIGHT SOILS BE AFFECTED BY CHANGES INCLIMATE? 37

IS THERE ANY EVIDENCE WHICH INDICA TES THATCLIMA TE CHANGES MA YHA VE ALREADY OCCURRED DUETO INCREASES IN GHG LEVELS? 38

CHAPTER 4 - THE GLOBAL CARBON CYCLE 40

WHAT PROCESSES EXIST FOR THE EXCHANGE OFCARBON BETWEEN THE ATMOSPHERE, THE OCEANS ANDTHE LAND? 40

HOW ARE EXCHANGES OF CARBON EXPRESSED? .. 41

WHAT IS THE PRESENT LEVEL OF CARBON EXCHANGEBETWEEN THE ATMOSPHERE, THE OCEANS AND THELAND? 45

CHAPTER 5 - TREES AND FORESTS AS SOURCES AND SINKS OFCARBON 45

HOW MUCH OF THE EARTH'S SURFACE IS PRESENTLYCOVERED BY FORESTS AND OTHER WOODYVEGETATION? 45

WHAT PROCESSES OCCUR IN TREES AND FORESTSWHICH CONTRIBUTE TO CHANGES IN LEVELS OF GHGS INTHE EARTH'S ATMOSPHERE? 45

v

17. WHA T CHANGES IN THE LEVEL OF THE OCEANS ARE EXPECTED DUE TO CL/MA TE CHANGE? ... . . . . . . 34

1B. HOW WILL PLANTS, INCLUDING TREES, BE INFLUENCED BY CHANGES IN THE LEVELS OF GHGs IN THE EARTH'S A TMOSPHERE AND RESUL TANT CHANGES IN TEMPERA TURE AND PRECIPITA TlON 1 . . ........ 34

19. HOW MIGHT SOILS BE AFFECTED BY CHANGES IN CL/MA TE? ............. ....... . .... ... .. 37

20. IS THERE ANY EVIDENCE WHICH !NDICA TES THA T CL/MA TE CHANGES MA YHA VE ALREADY OCCURRED DUE TO INCREASES IN GHG LEVELS? .............. 38

CHAPTER 4 - THE GLOBAL CARBON CYCLE . . . . . . . . . .. 40

21. WHA T PROCESSES EXIST FOR THE EXCHANGE OF CARBON BETWEEN THE A TMOSPHERE, THE OCEANS AND THE LAND? ...................... . ..... . 40

22. HOW ARE EXCHANGES OF CARBON EXPRESSED? . . 41

23. WHA T IS THE PRESENT LEVEL OF CARBON EXCHANGE BETWEEN THE A TMOSPHERE, THE OCEANS AND THE LAND? .............. . .. .. . . . . . ......... 45

CHAPTER 5 - TREES AND FORESTS AS SOURCES AND SINKS OF ~RBON .... . ..... .. ... . ... . ...... 45

24. HOW MUCH OF THE EARTH'S SURFACE IS PRESENTL Y COVERED BY FORESTS AND OTHER WOODY VEGETA TION? ......................... . . 45

25. WHA T PROCESSES OCCUR IN TREES AND FORESTS WHICH CONTRIBUTE TO CHANGES IN LEVELS OF GHGS IN THE EARTH'S ATMOSPHERE? ............ . ... 45

vi

HOW MUCH CARBON IS RELEASED AND HOW MUCH ISTAKEN UP ANNUALLY BY FORESTS? 47

DO DIFFERENT FOREST ECOSYSTEMS VA AY IN THEIRCAPACITY TO ABSORB AND STORE CARBON? . . . . 47

DO TREES AND FORESTS REMOVE CARBON FROM THEEARTH'S ATMOSPHERE AT DIFFERENT RATES DURINGDIFFERENT STAGES IN THEIR LIVES? 49

WHICH HUMAN ACTIVITIES IN FORESTS A AIDWOODLANDS CONTRIBUTE TO INCREASES IN THE LEVELSOF GHGS? 53

WHAT ARE THE CURRENT RATES OF DEFORESTATION INTHE WORLD'S FORESTS? 55

HOW ARE FOREST SOILS AFFECTED BYDEFORESTATION? 56

CHAPTER 6 - POSSIBLE EFFECTS OF CLIMATE CHANGE ONFORESTS 57

WHAT CHANGES IN GROWTH AND YIELD OF TREES ANDFORESTS CAN BE EXPECTED AS A RESULT OF CLIMA TECHANGE? 57

WHAT CHA NGES CAN BE EXPECTED IN THE NATURALRANGES OF TREE SPECIES AND PLANT COMMUNITIESDUE TO CLIMA TE CHANGE? 58

WHAT IS THE LIKELIHOOD THAT CLIMA TE CHANGECOULD THREA TEN SOME SPECIES OR PLANTCOMMUNITIES WITH EXTINCTION? 64

HOW MIGHT CLIMA TE CHANGE INFLUENCE THEINCIDENCE AND INTENSITY OF WILDFIRES? 66

vi

26. HOW MUCH CARBON IS RELEASED AND HOW MUCH IS TAKEN UP ANNUALL Y BY FORESTS? ........... 47

27. DO DIFFERENT FOREST ECOSYSTEMS VARY IN THEIR CAPACITY TO ABSORB AND STORE CARBON? . ... 47

2B. DO TREES AND FORESTS REMOVE CARBON FROM THE EARTH'S A TMOSPHERE A T DIFFERENT RA TES DURING DIFFERENT STAGES IN THEIR LIVES? ........... 49

29. WHICH HUMAN ACTIVITIES IN FORESTS AND WOODLANDS CONTRIBUTE TO INCREASES IN THE LEVELS OFGHGS? ...... . .. . . . . . .. .... . ......... 53

30. WHA T ARE THE CURRENT RA TES OF DEFORESTA TlON IN THE WORLD'S FORESTS? ................... 55

31 . HOW ARE FOREST SOILS AFFECTED BY DEFORESTA TlON? . . . . . . . . . . . . . . . . . . . . . . . .. 56

CHAPTER 6 - POSSIBLE EFFECTS OF CLIMATE CHANGE ON FORESTS . ..... ... . ...... ..... . .. .. 57

32. WHA T CHANGES IN GROWTH AND YIELD OF TREES AND FORESTS CAN BE EXPECTED AS A RESUL T OF CLlMA TE CHANGE? .................. . .... . ..... . 57

33. WHA T CHANGES CAN BE EXPECTED IN THE NA TURAL RANGES OF TREE SPECIES AND PLANT COMMUNITIES DUE TO CLlMA TE CHANGE? ................. 58

34. WHA T IS THE LIKELIHOOD THA T CLlMA TE CHANGE COULD THREA TEN SOME SPECIES OR PLANT COMMUNITIES WITH EXTINCTION? ............ 64

35. HOW MIGHT CLlMA TE CHANGE INFLUENCE THE INCIDENCE AND INTENSITY OF WILDFIRES? .... .. 66

vii

WHAT ARE THE EXPECTED EFFECTS OF CLIMA TE CHA NGEON FOREST HEALTH INCLUDING SUSCEPTIBILITY TOPESTS AND DISEASE OR DECLINE? 67

CHAPTER 7 - HELPING FORESTS ADAPT TO CLIMATECHANGE 74

HOW CAN WE RESPOND TO PREDICTED CLIMATECHANGE? 74

DO NATURAL PROCESSES EXIST WHICH CAN HELP TREESAND FORESTS ADAPT TO A CHANGING CLIMA TE? . 75

HOW CAN FOREST MANAGEMENT HELP FORESTS ADAPTTO CLIMA TE CHANGE? 75

WHAT CAN BE DONE TO HELP FORESTS ADAPT TOINCREASED HAZARDS OF WILDFIRE AND (OR) PEST ANDDISEASE OUTBREAKS WHICH COULD RESULT FROMCLIMA TE CHANGE? 76

CHAPTER 8 - THE ROLE FORESTS IN MITIGATINGTHE EFFECTS OF CLIMATE CHANGE 80 -

WHAT OPPORTUNITIES DO FORESTS AND FORESTMANAGEMENT OFFER FOR MITIGATING THE EFFECTS OFPREDICTED CLIMA TE CHANGE? 80

WHAT FEA TURES SHOULD CHARACTERIZE ACTIONSTAKEN TO MITIGA TE POTENTIAL EFFECTS OF CLIMA TECHANGE? 81

WHAT ADDITIONAL RESEARCH IS NEEDED TO MOREFULLY UNDERSTAND THE POTENTIAL EFFECTS OFCLIMA TE CHANGE ON TREES AND FORESTS ANDFORESTRY AND TO DEVELOP ADAPTATION ANDMITIGATION TACTICS? 81

vii

36. WHA TARE THE EXPECTED EFFECTS OF CLlMA TE CHANGE ON FOREST HEAL TH INCLUDING SUSCEPTIBILITY TO PESTS AND DISEASE OR DECLINE? ............ 67

CHAPTER 7 - HELPING FORESTS ADAPT TO CLIMATE CHANGE .......................... 74

37. HOW CAN WE RESPOND TO PREDICTED CLlMA TE CHANGE? .............................. 74

3B. DO NA TURAL PROCESSES EXIST WHICH CAN HELP TREES AND FORESTS ADAPT TO A CHANGING CLlMA TE? . 75

39. HOW CAN FOREST MANA GEMENT HELP FORESTS ADAPT TO CLlMA TE CHANGE? . . . . . . . . . . . . . . . . . . . .. 75

40. WHA T CAN BE DONE TO HELP FORESTS ADAPT TO INCREASED HAZARDS OF WILDFIRE AND (OR) PEST AND DISEASE OUTBREAKS WHICH COULD RESUL T FROM CLlMA TE CHANGE? . . . . . . . . . . . . . . . . . . . . . . .. 76

CHAPTER 8 - THE ROLE FORESTS IN MITIGATING THE EFFECTS OF CLIMATE CHANGE .. ... . 80

41. WHA T OPPORTUNITIES DO FORESTS AND FOREST MANAGEMENT OFFER FOR MITIGA TlNG THE EFFECTS OF PREDICTED CL/MA TE CHANGE? . . . . . . . . . . . . . .. 80

42. WHAT FEATURES SHOULD CHARACTERIZE ACTIONS TAKEN TO MITIGA TE POTENTIAL EFFECTS OF CLlMA TE CHANGE? ................... . ... . . .. .... 81

43. WHA T ADDITIONAL RESEARCH IS NEEDED TO MORE FULL Y UNDERSTAND THE POTENTIAL EFFECTS OF CL/MA TE CHANGE ON TREES AND FORESTS AND FORESTRY AND TO DEVELOP ADAPTA TION AND MITlGA TlON TACTICS? ..... ................ 81

44. DO INTERNATIONAL AGREEMENTS EXIST WHICHENCOURAGE DEVELOPMENT AND PROTECTION OFFORESTS TO ENHANCE THEIR ABILITY TO MITIGA TE THEEFFECTS OF CLIMA TE CHANGE? 83

45. HOW CAN THE TROPICAL FORESTS ACTION PROGRAMMEITFAP1 ASSIST IN DEVELOPING FOREST SECTORPROGRAMMES TO HELP MITIGATE EFFECTS OF CLIMA TECHANGE? 85

8A - REDUCING SOURCES OF GREENHOUSE GASES . . . . 86

46. WHAT ACTIONS CAN BE TAKEN TO REDUCE THECURRENT RATES OF TROPICAL DEFORESTATION ANDHOW MIGHT THIS AFFECT EMISSIONS OF GHGS FROMFORESTS? 86

47. WHAT CANSE DONE TO REDUCE THE FREQUENCY ANDSCALE OF FORESTS AND SAVANNA WOODLANDCONSUMED BY BIOMASS BURNING? 87

48. HOW CAN INCREASING THE EFFICIENCY OF BURNINGFUEL WOOD AND OTHER BIOFUELS REDUCE EMISSIONSOF GHGS? 90

49. HOW CAN USE OF WOOD AND OTHER "BIOFUELS" INPLACE OF FOSSIL FUELS HELP REDUCE THE LEVELS OFGHGS IN THE ATMOSPHERE? 92

50. HOW CAN MORE EFFICIENT TIMBER HARVESTINGOPERA TIONS REDUCE EMISSIONS OF GHGS FROMFORESTS? 93

8B - MAINTAINING EXISTING SINKS OF GREENHOUSEGASES 96

51. HOW CAN MANAGEMENT AND CONSERVATION OFNATURAL FORESTS ENHANCE THEIR CAPAC/TY TO FIXAND STORE CARBON? 96

viii

44. DO INTERNATIONAL AGREEMENTS EXIST WHICH ENCOURAGE DEVELOPMENT AND PROTECTION OF FORESTS TO ENHANCE THEIR ABILITY TO MITIGA TE THE EFFECTS OF CLlMA TE CHANGE? .... . ...... . .. 83

45. HOWCAN THE TROPICAL FORESTSACTlON PROGRAMME (TFAP) ASSIST IN DEVELOPING FOREST SECTOR PROGRAMMES TO HELP MITIGA TE EFFECTS OF CLlMA TE CHANGE? .. ............................ 85

8A - REDUCING SOURCES OF GREENHOUSE GASES . . . . 86

46. WHAT ACTIONS CAN BE TAKEN TO REDUCE THE CURRENT RA TES OF TROPICAL DEFOREST A TION AND HOW MIGHT THIS AFFECT EMISSIONS OF GHGS 'FROM FORESTS? . . ..... . . . . . . . . . . . . . . . . . . . . . .. 86

47. WHA T CAN BE DONE TO REDUCE THE FREQUENCY AND SCALE OF FORESTS AND SA VANNA WOODLAND CONSUMED BY BIOMASS BURNING? ...... . .... 87

48. HOW CAN INCREASING THE EFFICIENCY OF BURNING FUEL WOOD AND OTHER 810FUELS REDUCE EMISSIONS OFGHGS? . .. .................... .. ..... 90

49. HOW CAN USE OF WOOD AND OTHER "BIOFUELS" IN PLACE OF FOSSIL FUELS HELP REDUCE THE LEVELS OF GHGS IN THE ATMOSPHERE? . . . . . . . . . . . . . . . .. 92

50. HOW CAN MORE EFFICIENT TIMBER HARVESTING OPERA TlONS REDUCE EMISSIONS OF GHGS FROM FORESTS? ..................... . .. .. ... . 93

88 - MAINTAINING EXISTING SINKS OF GREENHOUSE GASES . .. . .. .. . .... . ................... 96

51. HOW CAN MANAGEMENT AND CONSERVATION OF NA TURAL FORESTS ENHANCE THEIR CAPACITY TO FIX AND STORE CARBON? ..................... 96

ix

WHAT USES OF FORESTS AND FOREST PRODUCTS AREMOST DESIRABLE FROM THE STANDPOINT OF LONGTERM CARBON STORAGE? 98

8C - EXPANDING SINKS OF GREENHOUSE GASES 99

HOW MUCH CARBON CAN BE FIXED IN WOOD AND SOILON A PER HECTARE BASIS IN FOREST PLANTA TIONS INBOREAL, TEMPERATE AND TROPICAL ZONES? . . 99

HOW MUCH ADDITIONAL AREA OF FOREST PLANTATIONSWOULD BE REQUIRED TO FULLY OFFSET PRESENTANNUAL INCREASES IN GHG LEVELS FROM ALLSOURCES? 100

TO WHAT EXTENT ARE SUITABLE LANDS AVAILABLE FORAFFORESTATION AND REFORESTATION? WHERE ARETHEY? 102

OTHER THAN AVAILABILITY OF LAND, WHAT OTHERCONSTRAINTS ARE THERE TO LARGE SCALEAFFORESTATION INITIATIVES? 105

WHAT ASSISTANCE IS AVAILABLE TO SUPPORTAFFORESTATION AND REFORESTA TION, PARTICULARL YAT THE INTERNATIONAL LEVEL? 106

HOW CAN AGROFORESTRY AND URBAN TREE PLANTINGSCONTRIBUTE TO THE MITIGATION OF CLIMA TECHANGE? 107

IS THE PLANTING OF TREES SOLELY FOR CO,ABSORPTION A SOUND POLICY CONSIDERING OTHERNEEDS FOR AVAILABLE LAND? 112

WHAT FOREST POLICIES SHOULD BE CONSIDERED AT THECOUNTRY LEVEL TO ADDRESS THE THREAT OF CLIMA TECHANGE? 113

LITERATURE CITED 114INDEX 123

Ix

52. WHA T USES OF FORESTS AND FOREST PRODUCTS ARE MOST DESIRABLE FROM THE STANDPOINT OF LONG TERM CARBON STORAGE? ..... . ... . ........ 98

8C • EXPANDING SINKS OF GREENHOUSE GASES. . . . .. 99

53. HOW MUCH CARBON CAN BE FIXED IN WOOD AND SOIL ON A PER HECTARE BASIS IN FOREST PLANTA TlONS IN BOREAL, TEMPERA TE AND TROPICAL ZONES? .... 99

54. HOW MUCH ADDITIONAL AREA OF FOREST PLANTA TIONS WOULD BE REQUIRED TO FULL Y OFFSET PRESENT ANNUAL INCREASES IN GHG LEVELS FROM ALL SOURCES? .... , , , , , , , , , . , , . , , , , , , , , , , .. 100

55. TO WHA T EXTENT ARE SUITABLE LANDS A VAILABLE FOR AFFORESTA TlON AND REFORESTA TlON? WHERE ARE THEY? .. , , , , , , , , , , , , , . , , ' , , , , , , , , , , . " 102

56. OTHER THAN A VAILABILlTY OF LAND, WHA T OTHER CONSTRAINTS ARE THERE TO LARGE SCALE AFFORESTA TlON INITIA TlVES? " ... ,""",. 1 05

57. WHA T ASSISTANCE IS A VAILABLE TO SUPPORT AFFORESTA TlON AND REFOREST A TlON, PARTlCULARL Y AT THE INTERNATIONAL LEVEL? , .. , .. " ,. , " 106

58. HOW CAN A GROFORESTRY AND URBAN TREE PLANTlNGS CONTRIBUTE TO THE MITIGA TlON OF CLlMA TE CHANGE? , , , , , ' , , , , , , , , , , , , , , , , , , , , , , ,. 107

59. IS THE PLANTING OF TREES SOLEL Y FOR ' C02

ABSORPTION A SOUND POLICY CONSIDERING OTHER NEEDS FOR A VAILABLE LAND? """"""" 112

60. WHA T FOREST POLICIES SHOULD BE CONSIDERED A T THE COUNTRY LEVEL TO ADDRESS THE THREA T OF CLlMA TE CHANGE? , ' . , ' , , , , , , , , . , , , . , , , , , , , . , , ,. 113

LITERATURE CITED " • . , •. . ,' . " " .. , . . " .,',.. 114 INDEX ., ' ,. ," ",",' . "."." ' . "' .'. ' ,.,' 123

LIST OF ACRONYMS AND ABBREVIATIONS

Carbon

CFC Chlorofluorocarbon

CH Methane

CO, Carbon dioxide

ENSO El Niño Southern Onillation

FAO Food and Agriculture Organization of theUnited Nations

FWD Foundation for Woodstove Dissemination.

FTTP Forests, Trees and People Programme

GCM General Circulation Model

GEF Global Environmental Facility

GHG Greenhouse gas

Gt Gigatonne (109 tonnes)

GWP Global Warming Potential

ha Hectare

IPCC Intergovernmental Panel on Climate Change

IPM Integrated pest management

NGO Non Government Organization

N20 Nitrous oxide

NO,, Nitrogen oxides

xi

C

CFC

CO2

ENSO

FAO

FWD

FTTP

GCM

GEF

GHG

Gt

GWP

ha

IPCC

IPM

NGO

N20

NO.

xl

LIST OF ACRONYMS AND ABBREVIATIONS

Carbon

Chlorofluorocarbon

Methane

Carbon dioxide

El Nino Southern Oscillation

Food and Agriculture Organization of the United Nations

Foundation for Woodstove Dissemination.

Forests, Trees and People Programme

General Circulation Model

Global Environmental Facility

Greenhouse gas

Gigatonne (10' tonnes)

Global Warming Potential

Hectare

Intergovernmental Panel on Climate Change

Integrated pest management

Non Government Organization

Nitrous oxide

Nitrogen oxides

xii

Pg Petagramme (10' tonnes)

ppbv Parts per billion by volume

ppmv Parts per million by volume

pptv Parts per trillion by volume

tC Tonnes of carbon

tC/ha Tonnes of carbon per hectare

TCP Technical Cooperation Programme (FAO)

TFAP Tropical Forests Action Programme

Tg Teragramme (10' tonnes)

UNCED United Nations Conference on Environmentand Development

UNDP United Nations Development Programme

UNEP United Nations Environment Programme

USDA United States Department of Agriculture

WB The World Bank

WMO World Meteorological Organization

WRI World Resources Institute

xii

Pg

ppbv

ppmv

pptv

tC

tC/ha

TCP

TFAP

Tg

UNCED

UNDP

UNEP

USDA

WB

WMO

WRI

Petagramme (10" tonnes)

Parts per billion by volume

Parts per million by volume

Parts per trillion by volume

Tonnes of carbon

Tonnes of carbon per hectare

Technical Cooperation Programme (FAO)

Tropical Forests Action Programme

Teragramme (10" tonnes)

United Nations Conference on Environment and Development

United Nations Development Programme

United Nations Environment Programme

United States Department of Agriculture

The World Bank

World Meteorological Organization

World Resources Institute

LIST OF TABLES

Table 2.1 - Direct global warming potentials of majorgreenhouse gases for a 100 year time horizon

24

Table 4.1 - Estimated distribution of the global carbonpool 41

Table 5.1 - Land area covered by forests and other woodedareas by region 46

Table 5.2 - Estimated annual rates of carbon exchange betweenthe world's forests and the atmosphere 48

Table 5.3 - Estimates of average above ground carbon/ha storedin various vegetation communities 50

Table 5.4 - Estimated carbon densities per unit of forest area invegetation and soils of the world's forests . . . 51

Table 8.1 - Carbon fixation rates for several tropical forestplantation species 99

Table 2.1 -

Table 4 .1 -

Table 5.1 -

Table 5.2 -

Table 5.3 -

Table 5.4 -

Table 8.1 -

xiii

LIST OF TABLES

Direct global warming potentia Is of major greenhouse gases for a 100 year time horizon

. ... .. . .. ........... . ...... . ... . 24

Estimated distribution of the global carbon pool ............ . ..... .. ....... .. 41

Land area covered by forests and other wooded areas by region . . . . . . . . . . . . . . . . . . . . .. 46

Estimated annual rates of carbon exchange between the world's forests and the atmosphere . . . . . 48

Estimates of average above ground carbon/ha stored in various vegetation communities. . . . . . . .. 50

Estimated carbon densities per unit of forest area in vegetation and soils of the world's forests . .. 51

Carbon fixation rates for several tropical forest plantation species . . . . . . . . . . . . . . . . . 99

xiv

LIST OF BOXES

Box 1.1 - Historic droughts in California and Patagonia . . 8

Box 1.2 - Did the rising of the Tibetan Plateau cool theworld? 13

Box 2.1 - What happened to atmospheric CO2 levels in1991? 20

Box 4.1 - Peat bogs, a major carbon sink 44

Box 5.1 - The role of forest plantations in New Zealand'scarbon balance 52

Box 6.1 - Will the future forests of the world be drier?63

Box 6.2 - Decline of Juniperus procera in Kenya - Anexample of a regional climate change? 73

Box 8.1 - Effects of tree planting on microclimate in Nanjing,China 111

xiv

Box 1 .1 -

Box 1.2-

Box 2 .1 -

Box 4.1

Box 5.1

Box 6.1 -

Box 6.2 -

Box 8. 'I -

LIST OF BOXES

Historic droughts in California and Patagonia . . 8

Did the rising of the Tibetan Plateau cool the world? .............. . ............. 13

What happened to atmospheric CO, levels in 1991? ..... .. .. . ..... . ............ 20

Peat bogs, a major carbon sink . . . . . . . . . .. 44

The role of forest plantations in New Zealand's carbon balance . . . . . . . . . . . . . . . . . . . . .. 52

Will the future forests of the world be drier? 63

Decline of Juniperus procer8 in Kenya - An example of a regional climate change? . . . . .. 73

Effects of tree planting on microclimate in Nanjing, China ...... .. . . ... . ............. 111

Figure 1.1 -

Figure 2.2 -

Figure 2.3 -

Figure 4.1 -

Figure 5.1 -

LIST OF FIGURES

XV

A generalised history of changes in temperature andprecipitation during geologic history. The curvesindicate departures from today's global means.Periods colder than today are shaded. Dashed linesindicate sparse data 6

Figure 2.1 - A simplified diagram of the greenhouse effect 16

Analysis of air trapped in Antarctic ice cores showsthat methane and carbon dioxide concentrationswere closely correlated with average temperaturesover the past 160 000 years 17

Changes in the levels of atmospheric CO, over thepast 250 years as indicated by analysis of ice coredata from the Antarctic and by atmosphericmeasurements at Mauna Loa, Hawaii, USA, since1958 24

Figure 3.1 - An example of a prediction of change in globalprecipitation for winter (top) and spring (bottom)produced by the UKHI GCM. Areas of decrease arestippled 29

Figure 3.2 - Increases in the number of tropical storms, whichcan damage many resources including forests, area possible, but uncertain outcome of global climatechange 33

Schematic representation of the global carbon cycleshowing movement of carbon between carbonsources and sinks 42

An aerial view of a brush fire in the Sudan. Roughly750 million ha of savanna vegetation are burnedannually, resulting in a massive release ofgreenhouse gases 55

Figure 1.1 -

Figure 2.1 -

Figure 2.2 -

Figure 2.3 -

Figure 3.1 -

Figure 3.2 -

Figure 4 .1 -

Figure 5.1 -

xv

LIST OF FIGURES

A generalised history of changes in temperature and precipitation during geologic history. The curves indicate departures from today's global means. Periods colder than today are shaded. Dashed lines indicate sparse data .. .. ... ... ......... 6

A simplified diagram of the greenhouse effect 16

Analysis of air trapped in Antarctic ice cores shows that methane and carbon dioxide concentrations were closely correlated with average temperatures over the past 160 000 years ............ 17

Changes in the levels of atmospheric CO2 over the past 250 years as indicated by analysis of ice core data from the Antarctic and by atmospheric measurements at Mauna Loa, Hawaii, USA, since 1958 ................... .. ... 24

An example of a prediction of change in global precIpitation for winter (top) and spring (bottom) produced by the UKHI GCM. Areas of decrease are stippled . . . . . . . . . . . . . . . . . . . . . . . . . .. 29

Increases in the number of tropical storms, which can damage many resources including forests, are a possible, but uncertain outcome of global climate change .......... .. . ... ........... 33

Schematic representation of the global carbon cycle showing movement of carbon between carbon sources and sinks . . . . . . . . . . . . . . . . . . .. 42

An aerial view of a brush fire in the Sudan. Roughly 750 million ha of savanna vegetation are burned annually, resulting in a massive release of greenhouse gases . . . . . . . . . . . . . . . . . . .. 55

xvi

Figure 6.1 - Pollen diagrams made from analysis of lakesediments in the Upper Peninsula of Michigan, USA.These data provide clues as to the composition offorests which occupied this area in the past . . 59

Figure 6.2 - Holdridge Life-Zone Classification of vegetationtypes for present day (upper) and under a doubledCO2 scenario of temperature 61

Figure 6.3- Possible redistribution of loblolly pine, Pinus taeda,in the southeastern USA due to a doubling ofatmospheric CO2 62

Figure 6.4 - Examples of species redistribution in high mountainregions due to a 2°C increase in mean annualtemperature: a = mountains of eastern Africaresulting in a relatively small increase in area and b= highlands of Uganda resulting in a neardisappearance of a high elevation vegetation zone

62

Figure 6.5 - A forest of Ab/es fraseri and Picea rubens straddlesthe highest ridges in the Black Mountains of NorthCarolina, USA. Forests such as these would beunable to shift their ranges upslope in response to awarming climate 65

Figure 6.6 - Insects such as the pine caterpillar, Dendrolimuspunctatus, a destructive defoliator of tropical pinesin Southeast Asia can undergo additional generationsin warmer climates 69

Figure 8.1 - A forester in Mexico's Yucatan Peninsula assessforest fuels. Knowledge of fuel conditions is animportant factor in planning forest fire managementprogrammes 89

xvi

Figure 6.1 - Pollen diagrams made from analysis of lake sediments in the Upper Peninsula of Michigan, USA. These data provide clues as to the composition of forests which occupied this area in the past .. 59

Figure 6.2 - Holdridge Life-Zone Classification of vegetation types for present day (upper) and under a doubled CO2 scenario of temperature ...... . ..... 61

Figure 6.3- Possible redistribution of loblolly pine, Pin us taeda, in the southeastern USA due to a doubling of atmospheric CO2 , • • • • • • • • • • • • • • . • • • •• 62

Figure 6 .4 - Examples of species redistribution in high mountain regions due to a 2'C increase in mean .annual temperature: a = mountains of eastern Africa resulting in a relatively small increase in area and b = highlands of Uganda resulting in a near disappearance of a high elevation vegetation zone

. ... . ...... . . . ...... . ..... . . . ... 62

Figure 6.5 - A forest of Abies (raseri and Picea rubens straddles the highest ridges in the Black Mountains of North Carolina, USA. Forests such as these would be unable to shift their ranges upslope in response to a warming climate . . . . . . . . . . . . . . . . .. 65

Figure 6.6 - Insects such as the pine caterpillar, Dendrolimus punctatus, a destructive defoliator of tropical pines in Southeast Asia can undergo additional generations in warmer climates . . . . ... ..... .. ..... 69

Figure 8.1 - A forester in Mexico's Yucatan Peninsula assess forest fuels. Knowledge of fuel conditions is an important factor in planning forest fire management programmes . . . . . . . . . . . . . . . . . . . . . . .. 89

Figure 8.2 -

Figure 8.3 -

xvii

A load of fuelwood is taken from a forest plantationto a village in Indonesia. Rural people in developingcountries rely heavily on fuelwood for cooking andheating. More efficient alternatives, resulting inlower GHG emissions are available 91

A comparison of residual carbon storage betweenconventional and reduced impact logging inMalaysia 95

Figure 8.4 - In Vietnam, a woman collects resin in a pineplantation. Non-wood forest products can provideeconomic incentives to manage and protect forests,thus maintaining their capacity to absorb and storecarbon 97

Figure 8.5 - Plantations of fast growing trees, such as thisplantation of Pinus radiata in Chile, can absorbatmospheric CO, while providing other benefits 101

Figure 8.6 - Shade trees, such as these neems planted along thestreets of Niamey, the capital of Niger, lowertemperatures and provide a more pleasantenvironment 109

Figure 8.2 -

Figure 8.3 -

Figure 8.4 -

Figure 8.5 -

Figure 8.6 -

xvH

A load of fuel wood is taken from a forest plantation to a village in Indonesia. Rural people in developing countries rely heavily on fuelwood for cooking and heating. More efficient alternatives, resulting in lower GHG emissions are available .. ...... 91

A comparison of residual carbon storage between conventional and reduced impact logging in Malaysia .. . .... .. .. ..... ..... . ... . 95

lA Vietnam, a woman collects resin in a pine plantation. Non-wood forest products can provide economic incentives to manage and protect forests, thus maintaining their capacity to absorb and store carbon.. ................. . ...... 97

Plantations of fast growing trees, such as this plantation of Pinus radiata in Chile, can absorb atmospheric CO, while providing other benefits 1 01

Shade trees, such as these neems planted along the streets of Niamey, the capital of Niger, lower temperatures and provide a more pleasant environment . . . . . . .. . . . . . . . . . . . .. 109

C//mate Change, Forests and Forest Management 1

INTRODUCTION

The likelihood of global climate change and its possible effects,including its effects on forests, is one of the most hotlydebated environmental issues of the decade of the 90s. Willthe Earth's climate change in the future? The answer must bean unqualified yes. There have been alternating periods ofcool and warm climate throughout our planet's 3.5 billion yearhistory. Therefore, there is no reason to expect that theEarth's present climate, during which virtually all humandevelopment has taken place, will remain constant.

The more important and difficult questions are:

How will the Earth's climate change?

How will a changing climate affect the abilitiesof human societies to maintain and enhancetheir quality of life?

What actions can be taken to adapt to ormitigate the effects of climate change?

Many scientists argue that the present period of relatively mildtemperatures which have dominated the Earth since the lastgreat continental ice sheets began to recede some 10 000years ago is a short interlude. They predict that another iceage will, once again, cover large areas of the Earth's surface.

A more near term concern is that the increasing evidence thatcertain human activities, such as burning of fossil fuels,conversion of forests to agricultural land at unprecedentedrates and other activities are causing significant, increases inthe levels of carbon dioxide (002) and other "greenhouse"gases in the atmosphere. These changes could lead to globalwarming at an unprecedented rate and could have seriousimplications for agriculture, fisheries, forestry and humandevelopment. Strategies for adapting to and mitigating the

Climate Change, Forests and Forest Management 1

INTRODUCTION

The likelihood of global climate change and its possible effects, including its effects on forests, is one of the most hotly debated environmental issues of the decade of the 90s. Will the Earth's climate change in the future? The answer must be an unqualified yes. There have been alternating periods of cool and warm climate throughout our planet's 3.5 billion year history. Therefore, there is no reason to expect that the Earth's present climate, during which virtually all human development has taken place, will remain constant.

The more important and difficult questions are:

1. How will the Earth's climate change?

2. How will a changing climate affect the abilities of human societies to maintain and enhance their quality of life?

3. What actions can be taken to adapt to or mitigate the effects of climate change?

Many scientists argue that the present period of relatively mild temperatures which have dominated the Earth since the last great continental ice sheets began to recede some 10 000 years ago is a short interlude. They predict that another ice age will, once again, cover large areas of the Earth's surface.

A more near term concern is that the increasing evidence that certain human activities, such as burning of fossil fuels, conversion of forests to agricultural land at unprecedented rates and other activities are causing significant. increases in the levels of carbon dioxide (CO,) and other "greenhouse" gases in the atmosphere. These changes could lead to global warming at an unprecedented rate and could have serious implications for agriculture, fisheries, forestry and human development. Strategies for adapting to and mitigating the

2 Climate Change, Forests and Forest Management

effects of an increased greenhouse effect are presently beingconsidered at the national, regional and international level.

There is much confusion and uncertainty associated with theclimate change issue. During the past decade, many studies,designed to improve our capacity to predict future climatictrends and the ways in which human society might beaffected, have been conducted. The results of these studiesare often conflicting and unclear.

The issues related to forestry are especially complex. Forestsand human uses of forests can contribute to increases inatmospheric levels of greenhouse gases. Forests are alsoaffected by changes in climate. In addition, trees and forests,because of their ability to absorb CO2 and store carbon inwoody tissue, offer an opportunity to help mitigate futureclimate change.

The complexity of forests, their relatively long life span andtheir multifaceted relationship with climate change pose manyquestions. How will forests be affected by climate change?How can foresters respond? Can forest management helpmitigate the effects of climate change?

The purpose of this paper is to provide a broad overview ofthe climate change issue as it relates to forestry and forestmanagement. It also attempts to provide some insights as tohow foresters can respond to the challenges posed by possiblefuture climate change. The material is presented in questionand answer form in eight chapters. These focus on variousaspects of the climate change issue including the dynamicnature of climate, the greenhouse effect, predictions of climatechange and its effects, the global carbon cycle, forests assources and sinks of carbon, the effects of predicted climatechange on forests, strategies for helping forests adapt toclimate change and the ways in which forests can mitigate theeffects of climate change.


effects of an increased greenhouse effect are presently being considered at the national , regional and international level.

There is much confusion and uncertainty associated with the climate change issue, During the past decade, many studies, designed to improve our capacity to predict future climatic trends and the ways in which human society might be affected , have been conducted . The results of these studies are often conflicting and unclear.

The issues related to forestry are especially complex. Forests and human uses of forests can contribute to increases in atmospheric levels of greenhouse gases. Forests are also affected by changes in climate . In addition, trees and forests, because of their ability to absorb CO2 and store carbon in woody tissue, offer an opportunity to help mitigate future climate change .

The complexity of forests, their relatively long life span and their multifaceted relationship with climate change pose many questions. How will forests be affected by climate change? How can foresters respond? Can forest management help mitigate the effects of climate change 7

The purpose of this paper is to provide a broad overview of the climate change issue as it relates to forestry and forest management. It also attempts to provide some insights as to how foresters can respond to the challenges posed by possible future climate change. The material is presented in question and answer form in eight chapters. These focus on various aspects of the climate change issue including the dynamic nature of cl imate, the greenhouse effect, predictions of climate change and its effects, the global carbon cycle, forests as sources and sinks of carbon, the effects of predicted climate change on forests, strategies for helping ' forests adapt to climate change and the ways in which forests can mitigate the effects of climate change .


The material contained in this paper is designed for use byfield foresters, programme managers and policy advisors at thenational, regional and international level.


The material contained in this paper is designed for use by field foresters, programme managers and policy advisors at the national, regional and international level.

4 C//mate Change, Forests and Forest Management

Chapter 1THE EARTH'S CLIMATE - A DYNAMIC ENTITY

HOW ARE WEATHER AND CLIMA TE DEFINED?

Weather is the atmospheric condition prevailing in an area ata given time, resulting in heat or cold, clearness or cloudiness,dryness or moisture, wind or calm.

Climate, as defined by the World Meteorological Organization(WMO), is the "synthesis of weather conditions in a given areaas defined by long term statistics of the variables of the stateof the atmosphere". Seasonal changes such as the transitionfrom winter to spring, summer and autumn in temperate zonesand from wet to dry in the tropics are also part of climate.

Climate is a key factor which determines the distribution ofplants and animals and in the formation of soils through theweathering of geological materials and the decomposition orpreservation of organic matter.

TO WHAT EXTENT HAS THE EARTH'S CLIMA TECHANGED DURING THE COURSE OF GEOLOGICHISTORY?

While the Earth's climate has been sufficiently stable tosupport life for millions of years, climate is dynamic andsubject to change. There is ample evidence from the fossilrecord and other indicators such as tree ring widths, growthrates of marine organisms and types of vegetation, asindicated by fossil pollen, that the Earth's climate has beencharacterized by periods of warm and cool weather ever sinceits existence (Fig 1.1). For example, over 230 million yearsago, during the latter part of the Palaeozoic Era, glacierscovered much of today's tropics. During much of theMesozoic Era, however, when dinosaurs and other reptiles


Chapter 1 THE EARTH'S CLIMATE - A DYNAMIC ENTITY

1. HOW ARE WEA THER AND CL/MA TE DEFINED?

Weather is the atmospheric condition prevailing in an area at a given time, resulting in heat or cold, clearness or cloudiness, dryness or moisture, wind or calm.

Climate, as defined by the World Meteorological Organization (WMO). is the "synthesis of weather conditions in a given area as defined by long term statistics of the variables of the state of the atmosphere". Seasonal changes such as the transition from winter to spring, summer and autumn in temperate zones and from wet to dry in the tropics are also part of climate.

Climate is a key factor which determines the distribution of plants and animals and in the formation of soils through the weathering of geological materials and the decomposition or preservation of organic matter.

2. TO WHA T EXTENT HAS THE EARTH'S CL/MA TE CHANGED DURING THE COURSE OF GEOLOGIC HISTORY?

While the Earth's climate has been sufficiently stable to support life for millions of years, climate is dynamic and subject to change. There is ample evidence from the fossil record and other indicators such as tree ring widths, growth rates of marine organisms and types of vegetation, as indicated by fossil pollen, that the Earth's climate has been characterized by periods of warm and cool weather ever since its existence (Fig 1.1). For example, over 230 million years ago, during the latter part of the Palaeozoic Era, glaciers covered much of today's tropics. During much of the Mesozoic Era, however, when dinosaurs and other reptiles


dominated the Earth (180 million to 65 million years ago),temperatures were much warmer than they are today.

Over the past million years, the Earth's climate has beencharacterized by long periods of cold weather whencontinental glaciers covered large areas. Each of these lastedfrom 80 000 to 100 000 years and were interspersed byshorter periods of warmer weather which ranged from 10 000to 15 000 years each. At the peak of the last glacial period,some 18 000 years ago, ocean levels were 130 m lower thanthey are today. The Bahamas were a substantial land massduring that time and the Sahel region of Africa was a desert.The continental glaciers began to retreat about 10 000 yearsago. Some 6 000 years ago, as the glaciers were still inretreat, the Earth entered a period during which averagetemperatures were about what they are today but with slightlywarmer summers and colder winters. Rainfall increased overthe African Sahel and Lake Chad rose to more than 40 mabove its present level. Human cultures in Africa wereconsiderably more advanced than those in Europe. As theglacial ice sheets continued to retreat northvvard, the Sahelagain became a region of marginal rainfall, with its northernregions invaded by the Sahara desert.

Many scientists believe that the present period of relativelymild temperatures which we enjoy today will eventually giveway to another ice age (Easterling 1990, Harrington 1987).

3, WHAT CHANGES HA VE OCCURRED IN THE EARTH'SCLIMA TE SINCE THE BEGINNING OF RECORDEDHUMAN HISTORY?

Historical records show that over the past 1 100 years, theEarth has experienced swings in climate, at least on a regionalbasis, which have been sufficiently stable and have persistedlong enough to be considered clirnate changes (Easterling1990).


dominated the Earth (1 80 million to 65 million years ago), temperatures were much warmer than they are today.

Over the past million years, the Earth's climate has been characterized by long periods of cold weather when continental glaciers covered large areas. Each of these lasted from 80 000 to 100 000 years and were interspersed by shorter periods of warmer weather which ranged from 10 000 to 15 000 years each. At the peak of the last glacial period, some 18 000 years ago, ocean levels were 130 m lower than they are today. The Bahamas were a substantial land mass during that time and the Sahel region of Africa was a desert. The continental glaciers began to retreat about 10 000 years ago. Some 6 000 years ago, as the glaciers were still in retreat, the Earth entered a period during which average temperatures were about what they are today but with slightly warmer summers and colder winters. Rainfall increased over the African Sahel and Lake Chad rose to more than 40 m above its present level. Human cultures in Africa were considerably more advanced than those in Europe. As the glacial ice sheets continued to retreat north""ard, the Sahel again became a region of marginal rainfall, with its northern regions invaded by the Sahara desert.

Many scientists believe that the present period of relatively mild temperatures which we enjoy today will eventually give way to another ice age (Easterling 1990, Harrington 1987).

3. WHA T CHANGES HA VE OCCURRED IN THE EARTH'S CL/MA TE SINCE THE BEGINNING OF RECORDED HUMAN HISTORY?

Historical records show that over the past 1 100 years, the Earth has experienced swings in climate, at least on a regional basis, which have been sufficiently stable and have persisted long enough to be considered cl imate changes (Easterling 1990).


1.8

65

225

570

1000

2000

3000

4000

4600

4

AoN

Figure 1.1 - A generalised history of changes in temperature andprecipitation during geologic history. The curves indicate departuresfrom today's global means. Periods colder than today are shaded.Dashed lines indicate sparse data (Source: Goodess et al (1992).

Quaternary

Pliocene IIMiocene

Oligocene

EocenePalaeocene

Cretaceous

Jurassic

Triassic

Permian

411

4INS '

Carboniferous

Devonian

Silunan

Ordovician

Cambrian

1.

1

I1

.___I____"--.1

i'....

-,,

X

X

presentdry wet

MEAN GLOBAL MEAN GLOBALTEMPERATURE PRECIPITATION

presentcod warm

6

65

m ~

~ >-

570

1000

2000

3000

4000

4600

Climate Change, Forests and Forest Management

Cretaceous

Jurassic

Triassic

Silurian

Ordovician

MEAN GLOBAL TEMPERATURE

MEAN GLOBAL PRECIPITATION

-i en Jl ::j » ::0 -<

~ (f)

2 ~

:Ii r-» en 0 N 0 0

1l ::0

[lJ » ;:: CD '!l » z

Figure 1.1 - A generalised history of changes in temperature and precipitation during geologic history. The curves indicate departures from today's global means. Periods colder than today are shaded. Dashed lines indicate sparse data (Source: Goodess et aI (1992).


During the period in European history known as the MiddleAges, a warm climate, lasting from about A.D. 900 to A.D.1 200 dominated most of Europe and was known as theMedieval Optimum. This period allowed human habitation toextend into regions which would be considered climatically tooharsh today. During the Medieval Optimum, oats and barleywere grown in Iceland and vineyards flourished in southernEngland. Canadian forests extended north for a considerabledistance from where they are today, agricultural settlementsflourished in the northern highlands of Scotland and a Vikingcolony was established in Greenland.

The Medieval Optimum ended during the 13th century andwas replaced by 600 years of pronounced cooling. As thecooling intensified, this period became known as the Little IceAge. Snow and ice cover were more extensive during thisperiod than at any time since the Pleistocene Period and itsextensive glaciers. Viking colonies which existed in Greenlandbetween AD 985 and 1500 died out (McGovern 1981). NorthAmerican forests retreated southward and canals in NorthernEurope were often frozen throughout the winter, bringingwater transportation to a halt.

By the time the Little Ice Age lessened its grip on Europe'sclimate during the mid-1800s, various climatic parameterssuch as temperature and precipitation were beginning to beroutinely recorded 1. These data show that by the end of the19th century, a warming trend began to occur in both thenorthern and southern hemispheres. This trend reached aninitial peak during the 1930's. In the years immediatelyfollowing, global temperatures cooled slightly before resumingtheir upward trend. The cooling trend was more pronouncedin the northern hemisphere.

Temperature and precipitation records for parts of Europe are available asfar back as the 12th century. A summary of wet and dry summers in northernGermany is given by Finck (1985).


During the period in European history known as the Middle Ages, a warm climate, lasting from about A.D. 900 to A.D. 1200 dominated most of Europe and was known as the Medieval Optimum. This period allowed human habitation to extend into regions which would be considered climatically too harsh today. During the Medieval Optimum, oats and barley were grown in Iceland and vineyards flourished in southern England. Canadian forests extended north for a considerable distance from where they are today, agricultural settlements flourished in the northern highlands of Scotland and a Viking colony was established in Greenland.

The Medieval Optimum ended during the 13th century and was replaced by 600 years of pronounced cooling. As the cooling intensified, this period became known as the Little Ice Age. Snow and ice cover were more extensive during this period than at any time since the Pleistocene Period and its extensive glaciers. Viking colonies which existed in Greenland between AD 985 and 1500 died out (McGovern 1981). North American forests retreated southward and canals in Northern Europe were often frozen throughout the winter, bringing water transportation to a halt.

By the time the Little Ice Age lessened its grip on Europe's climate during the mid-1800s, various climatic parameters such as temperature and 'precipitation were beginning to be routinely recorded'. These data show that by the end of the 19th century, a warming trend began to occur in both the northern and southern hemispheres. This trend reached an initial peak during the 1930's. In the years immediately following, global temperatures cooled slightly before resuming their upward trend. The cooling trend was more pronounced in the northern hemisphere.

~ Temperature and precipitation records for parts of Europe are available 8S

far beck as the 12th century_ A summary of wet end dry summers in northern Germany is given by Finck (1985).


Box 1.1 Historic droughts in California andPatagonia.

While Europe was basking in the MedievalOptimurn, other parts of the worldapparently were suffering from prolongeddrought. According to a recently completedstudy, which included analysis of ancientsubmerged tree stumps, the area of presentday California, USA, was affected by twolong and severe droughts during most of theMedieval Optimum. These were separatedby a period of unusual wetness whichlasted less than a century. The first ofthese droughts lasted for more than twocenturies. The second persisted for over140 years. There is evidence from thePatagonia Region of South America that italso was affected by drought during thistime period.

The droughts in California may have beenthe result of a northward shift ofsummertime storms.

California is presently home to 30 millionpeople. Consequent/y, a present daydrought of this magnitude would bedevastating (Stine 1994).


Box 1.1 Historic droughts in California and Patagonia.

While Europe was basking in the Medieval Optimum, other parts of the world apparently were ·suffering from prolonged drought. According to a recently completed study, which included analysis of ancient submerged tree stumps, the area of present day California, USA, was affected by two long and severe droughts during most of the Medieval Optimum. These were separated by a period of unusual wetness which lasted less than a century. The first of these droughts lasted for more than two centuries. The second persisted for over 140 years. There is evidence from the Patagonia Region of South America that it also was affected by drought during this time period.

The droughts in California may have been the result of a northward shift of summertime storms.

California is presently home to 30 million people. Consequently, a present day drought of this magnitude would be devastating (Stine 1994).


The world climatic record for the past two decades indicatesthat global surface air temperatures have increased above the1930 maximums. This warming trend extends to both theSouthern and Northern Hemisphere (Couglan and Nyenzi 1990)and has resulted in a global mean surface temperature increaseof about 0.45° C since the middle of the last century.

4. WHAT FACTORS CAN CAUSE CHA NGES IN THEEARTH'S CLIMA TE?

Changes in the Earth's temperature and associated changes inclimate have complex causes. These can be classified into thefollowing categories:

Astronomical factors - such as changes in solaractivity, variations in the eccentricity of the Earth'sorbit around the sun, changes in the tilt of the Earth'saxis (obliquity) precession of the Earth's axis andcollisions with asteroids or comets.

Geological factors - such as continental drift, changesin the topography of the ocean floor, volcaniceruptions, mountain building, erosion and weathering ofrock.

Oceanic Factors - such as the El Niño effect, changesin ocean circulation, sea level changes, ice formation,phytoplankton blooms and dimethysulphide production.

Land Surface Factors - including the effect ofvegetation on surface albedo (the whiteness or degreeof reflection of incident light from an object), andevapo-transpiration, open water effects includingirrigation and dust.


The world climatic record for the past two decades indicates that global surface air temperatures have increased above the 1930 maximums. This warming trend extends to both the Southern and Northern Hemisphere (Couglan and Nyenzi 1990) and has resulted in a global mean surface temperature increase of about 0.450 C since the middle of the last century.

4. WHA T FACTORS CAN CAUSE CHANGES IN THE EARTH'S CL/MA TE?

Changes in the Earth's temperature and associated changes in climate have complex causes. These can be classified into the following categories:

Astronomical factors - such as changes in solar activity, variations in the eccentricity of the Earth 's orbit around the sun, changes in the tilt of the Earth's axis (obliquity) precession of the Earth's axis and collisions with asteroids or comets.

Geological factors - such as continental drift, changes in the topography of the ocean floor, volcanic eruptions, mountain building, erosion and weathering of rock.

Oceanic Factors - such as the El Niiio effect, changes in ocean circulation, sea level changes, ice formation, phytoplankton blooms and dimethysulphide production.

Land Surface Factors - including the effect of vegetation on surface albedo (the whiteness or degree of reflection of incident light from an object). and evapo-transpiration, open water effects including irrigation and dust.


Atmospheric Factors - such as the effect of greenhousegases, sulphur dioxide and air pollutants, cloud effectsand interactions between the air, the land and the sea.

Some examples of the influence of these factors on globalclimate are described in the following paragraphs.

Changes in solar activity, such as the frequency and intensityof sunspots, or the gradual warming of the sun as its supplyof hydrogen is consumed, are believed to have significanteffects on climate. The virtual cessation of sunspot activityfor about 70-80 years in the 17th century, for example,coincides with the peak of the Little Ice Age, a period when aseries of disastrous harvests in Europe resulted in decades ofhardship and social unrest. The warming trend, whichfollowed the Little Ice Age, coincided with a resumption insunspot activity. The recent period of warmer temperatures,is associated with exceptionally strong sunspot activitybeginning in the late 1980s (Harrington 1987, Windelius andTucker 1990). However the measured increase in solar energyreceived by the Earth during peaks of sunspot activity doesnot appear to be sufficient to cause significant changes inclimate.

In rare instances, large asteroids have collided with the Earth.Such a collision can have a number of catastrophic effects,including the development of a layer of fine dust in theatmosphere which reduces the amount of solar energyreaching the Earth's surface. This can cause reducedtemperatures and light intensities. Some scientists believethat the collision of an asteroid of about 10 km in diameterwith the Earth, some 65 million years ago, resulted in thedrastic cooling that brought an end to the age of dinosaurs.Approximately one half of the genera of plants and animalsliving during this period became extinct (Harrington 1987).

The Milankovitch theory of ice age occurrence is based on longterm variation in solar radiation received at the polar latitudes


A tmospheric Factors - such as the effect of greenhouse gases, sulphur dioxide and air pollutants, cloud effects and interactions between the air, the land and the sea.

Some examples of the influence of these factors on global climate are described in the following paragraphs.

Changes in solar activity, such as the frequency and intensity of sunspots, or the gradual warming of the sun as its supply of hydrogen is consumed, are believed to have significant effects on climate . The virtual cessation of sunspot activity for about 70-80 years in the 17th century, for example , coincides with the peak of the Little Ice Age, a period when a series of disastrous harvests in Europe resulted in decades of hardship and social unrest . The warming trend, which followed the Little Ice Age, coincided with a resumption in sunspot activity. The recent period of warmer temperatures, is associated with exceptionally strong sunspot activity beginning in the late 1980s (Harrington 1987, Windelius and Tucker 1990). However the measured increase in solar energy received by the Earth during peaks of sunspot activity does not appear to be sufficient to cause significant changes in climate.

In rare instances, large asteroids have collided with the Earth. Such a collision can have a number of catastrophic effects, including the development of a layer of fine dust in the atmosphere which reduces the amount of solar energy reaching the Earth's surface . This can cause reduced temperatures and light intensities. Some scientists believe that the collision of an asteroid of about 10 km in diameter with the Earth, some 65 million years ago, resulted in the drastic cooling that brought an end to the age of dinosaurs. Approximately one half of the genera of plants and animals living during this period became extinct (Harrington 1987).

The Milankovitch theory of ice age occurrence is based on long term variation in solar radiation received at the polar latitudes


during certain seasons of the year. These are caused bychanges in the eccentricity of the Earth's orbit around the sun,which varies between the limits of 0 and 0.06 with an averageperiod of 93 000 years; the angle of tilt of the Earth's axis,which varies between 22.1 and 24.5° with an average of41 000 years and the precession of the Earth's axis, whichvaries with an average period of 21 000 years (Weertman1976).

Volcanoes occasionally erupt with such violence that largequantities of dust and gas are projected high into theatmosphere. Particles which reach the stratosphere maypersist for several years. They cause cooler temperatures byreflecting solar radiation. The Little Ice Age was a periodcharacterized by frequent volcanic activity when compared tothe present century. The eruption of the Indonesian volcano,Tambora in 1815, the largest eruption in recorded history, wasfollowed by a period of cool weather in portions of Europe,North America and possibly other parts of the world, knownas "The Year Without Summer." This resulted in a failure ofthe corn crop in portions of the United States and massivecrop failures in western Europe (Stommel and Stommel 1983).In Ghent, Belgium, for example, the summer of 1816 was thecoldest recorded between the years 1753 and 1960 (Gommes1980). Volcanic emissions due to the eruption of El Chichónin Mexico in 1982 and Pinatubo in the Philippines in 1991 alsocaused a slight cooling effect.

The ocean plays an essential role in the global climate system.Over half of the solar radiation reaching the Earth's surface isfirst absorbed by the ocean, where it is stored andredistributed by ocean currents before escaping into theatmosphere. The ocean currents are driven by the exchangeof momentum, heat and water between the ocean and theatmosphere (Cubasch and Cess 1990).

An ocean current which is known to have a significantinfluence on global climate is known as El Niño (Spanish for


during certain seasons of the year. These are caused by changes in the eccentricity of the Earth's orbit around the sun, which varies between the limits of 0 and 0.06 with an average period of 93 000 years; the angle of tilt of the Earth's axis, which varies between 22.1 and 24.5° with an average of 41 000 years and the precession of the Earth's axis, which varies with an average period of 21 000 years (Weertman 1976).

Volcanoes occasionally erupt with such violence that large quantities of dust and gas are projected high into the atmosphere. Particles which reach the stratosphere may persist for several years . They cause cooler temperatures by reflecting solar radiation. The Little Ice Age was a period characterized by frequent volcanic activity when compared to the present century. The eruption of the Indonesian volcano, Tambora in 1815, the largest eruption in recorded history, was followed by a period of cool weather in portions of Europe, North America and possibly other parts of the world, known as "The Year Without Summer." This resulted in a failure of the corn crop in portions of the United States and massive crop failures in western Europe (Stommel and Stommel 1983). In Ghent, Belgium, for example, the summer of 1816 was the coldest recorded between the years 1753 and 1960 (Gommes 1980). Volcanic emissions due to the eruption of El Chich6n in Mexico in 1982 and Pinatubo in the Philippines in 1991 also caused a slight cooling effect.

The ocean plays an essential role in the global climate system . Over half of the solar radiation reaching the Earth's surface is first absorbed by the ocean, where it is stored and redistributed by ocean currents before escaping into the atmosphere. The ocean currents are driven by the exchange of momentum, heat and water between the ocean and the atmosphere (Cubasch and Cess 1990) .

An ocean current which is known to have a significant influence on global climate is known as El Nilio (Spanish for

12 Clima te Change, Forests and Forest Management

Christ Child). El Niño is a warm ocean current that typicallyappears along the coast of western South America aroundChristmas and lasts for several months. An El Niño is initiatedby the Southern Oscillation (ENSO), which arises from thegradient between a low pressure system which lies overportions of Indonesia and Malaysia and a high pressure systemin the South Pacific. When the difference in pressure betweenthese two systems is reduced, the westward trade winds areweakened, causing a warming of the ocean surface off thecoast of Peru. This causes the low pressure system to shifteastward and leads to a decrease in rainfall over Malaysia andIndonesia and increased precipitation over the west coast ofCentral and South America. A particularly severe ENSO during1982-83 caused a severe drought on the island of Borneoresulting in the most extensive forest fires in recorded history.Approximately 3.5 million ha of primary and secondary rainforests in East Kalimantan, Indonesia were burned as a resultof these fires (Goldammer and Seibert 1990). This sameENSO resulted in severe storms and massive flooding alongthe west coast of South America. ENSO events are known toinfluence weather worldwide. This is the principal global scaleenvironmental factor which affects Atlantic seasonal hurricaneactivity. Hurricanes are suppressed during seasons whenwarm equatorial eastern and central Pacific watertemperatures occur. Activity is enhanced during seasons withcold water climates (Grey 1993). There is also evidence thatENSOs are linked to below average rainfall in southern Africa(Cane et al 1994).

The oceans also contain chemical and biological mechanismswhich are important in controlling CO2. CO2 is transferredfrom the atmosphere into the ocean by differences in thepartial pressure of CO2 in the ocean and the lowest layers ofthe atmosphere. The oceans also contain phytoplanktonwhich convert dissolved CO2 into particulate carbon whichsinks into deep water (Cubasch and Cess 1990).


Christ Child). El Nino is a warm ocean current that typically appears along the coast of western South America around Christmas and lasts for several months. An El Nino is initiated by the Southern Oscillation (ENSO), which arises from the gradient between a low pressure system which lies over portions of Indonesia and Malaysia and a high pressure system in the South Pacific. When the difference in pressure between these two systems is reduced , the westward trade winds are weakened, causing a warming of the ocean surface off the coast of Peru. This causes the low pressure system to shift eastward and leads to a decrease in rainfall over Malaysia and Indonesia and increased precipitation over the west coast of Central and South America. A particularly severe ENSO during 1982-83 caused a severe drought on the island of Borneo resulting in the most extensive forest fires in recorded history. Approximately 3.5 million ha of primary and secondary rain forests in East Kalimantan, Indonesia were burned as a result of these fires (Goldammer and Seibert 1990). This same ENSO resulted in severe storms and massive flooding along the west coast of South America. ENSO events are known to influence weather worldwide. This is the principal global scale environmental factor which affects Atlantic seasonal hurricane activity. Hurricanes are suppressed during seasons when warm equatorial eastern and central Pacific water temperatures occur. Activity is enhanced during seasons with cold water climates (Grey 1993). There is also evidence that ENSOs are linked to below average rainfall in southern Africa (Cane et al 1994).

The oceans also contain chemical and biological mechanisms which are important in controlling CO, . CO, is transferred from the atmosphere into the ocean by differences in the partial pressure of CO, in the ocean and the lowest layers of the atmosphere. The oceans also contain phytoplankton which convert dissolved CO, into particulate carbon which sinks into deep water (Cubasch and Cess 1990).


Box 1.2 Did the rising of the TibetanPlateau cool the world?

The Tibetan Plateau, which lies between theHimalayas in the south and the KunlunMountains in the north is believed to havebeen caused by continental drift ending withIndia and Asia colliding. The Plateau coversabout 2.2 million square kilometres and isequivalent to 0.4% of the Earth's totalsurface area. Average elevation is 5

kilometres above sea level. It has beensuggested that the uplift of the plateaucreated patterns of air circulation whichbring water laden air off the Indian Ocean insummer and deliver monsoonal rains to theIndian subcontinent. Atmospheric carbondioxide is dissolved in the torrential rains,forming a weak solution of carbonic acidwhich erodes the plateau's bedrock and isdelivered to the ocean as bicarbonates.This process is believed to have removedlarge quantities of carbon dioxide from theEarth's atmosphere resulting in a globalcooling effect (Patterson 1993).


Box 1.2 Did the rising of the Tibetan Plateau cool the world?

The Tibetan Plateau, which lies between the Himalayas in the south and the Kunlun ivlountains in the north is believed to have been caused by continental drift ending with India and Asia colliding. The Plateau covers about 2.2 million square kilometres and is equivalent to 0.4% of the Earth's total surface area. Average elevation is 5 kilometres above sea level. It has been suggested that the uplift of the plateau created patterns of air circulation which bring water laden air off the Indian Ocean in summer and deliver monsoonal rains to the Indian subcontinent. Atmospheric carbon dioxide is dissolved in the torrential rains, forming a weak solution of carbonic acid which erodes the plateau's bedrock and is delivered to the ocean as bicarbonates. This process is believed to have removed large quantities of carbon dioxide from the Earth's atmosphere resulting in a global cooling effect (Patterson 1993).

13


The average temperature of the Earth is presently 15°C. Thisis largely due to the effects of radiative or "greenhouse" gaseswhich are present in the atmosphere. Without these gases,the Earth's average temperature would be -18°C. This isequivalent to the temperature of the surface of the moon andlife, as we know it, would not be possible. Most of the shortwavelength radiation which the Earth receives from the sunpasses through these gases and warms the Earth's surface.The surface, in turn, emits long wave thermal radiation backto the atmosphere. This is absorbed by the greenhouse gasesand heats the atmosphere. The atmosphere emits long waveradiation into space and downward to further heat the Earth'ssurface (See question 5 for a more detailed explanation).


The average temperature of the Earth is presently 15·C. This is largely due to the effects of radiative or "greenhouse" gases which are present in the atmosphere. Without these gases, the Earth's average temperature would be -1S·C. This is equivalent to the temperature of the surface of the moon and life, as we know it, would not be possible. Most of the short wavelength radiation which the Earth receives from the sun passes through these gases and warms the Earth's surface. The surface, in turn, emits long wave thermal radiation back to the atmosphere. This is absorbed by the greenhouse gases and heats the atmosphere. The atmosphere emits long wave

. radiation into space and downward to further heat the Earth's surface (See question 5 for a more detailed explanation).


Chapter 2THE GREENHOUSE EFFECT

5. WHAT IS THE "GREENHOUSE EFFECT" AND HOWDOES IT INFLUENCE THE EA i TH'S CLIMA TE?

The greenhouse effect is the retention of heat in the loweratmosphere due to absorption and re-radiation by clouds andcertain gases. The Earth receives its energy from the sun assolar radiation. Short-wave solar (visible) radiation receivedfrom the sun passes through the atmosphere with little or nointerference and warms the Earth's surface. Long-wavethermal radiation emitted by the warmed surface of the Earthis partially absorbed by a number of trace or "greenhouse"gases (GHGs). These gases occur in small amounts in theatmosphere and reflect the long wave thermal radiation in alldirections. Some of the radiation is directed downwardstoward the Earth's surface (Fig 2.1).

The amount of GHGs in the atmosphere can influence globaltemperatures. If these gases were to increase, temperaturescould rise. If they were to decrease, global temperatureswould cool.

The greenhouse effect is a well understood phenomenonbased on established scientific principles. The Earth's averagesurface temperature, for example, is warmer by about 33°Cthan it would be without the presence of these gases.Satellite observations of the radiation emitted from the Earth'ssurface and through the atmosphere confirm the effects ofgreenhouse gases. The composition of the atmospheres ofVenus, the Earth and Mars are quite different but their surfacetemperatures are in general agreement with the principles ofgreenhouse effect. Finally, measurements from ice coresgoing back 160 000 years show that the Earth's temperatureclosely paralleled the amount of carbon dioxide and methane,

Climate Change. Forests and Forest Management 15

Chapter 2 THE GREENHOUSE EFFECT

5. WHA T IS THE "GREENHOUSE EFFECT" AND HOW DOES IT INFLUENCE THE EARTH'S CLlMA TE7

The greenhouse effect is the retention of heat in the lower atmosphere due to absorption and re-radiation by clouds and certain gases. The Earth receives its energy from the sun as solar radiation. Short-wave solar (visible) radiation received from the sun passes through the atmosphere with little or no interference and warms the Earth's surface. Long-wave thermal radiation emitted by the warmed surface of the Earth is partially absorbed by a number of trace or "greenhouse" gases (GHGs) . These gases occur in small amounts in the atmosphere and reflect the long wave thermal radiation in all directions. Some of the radiation is directed downwards toward the Earth's surface (Fig 2.1).

The amount of GHGs in the atmosphere can influence global temperatures. If these gases were to increase, temperatures could rise. If they were to decrease, global temperatures would cool.

The greenhouse effect is a well understood phenomenon based on established scientific principles. The Earth's average surface temperature, for example, is warmer by about 33°C than it would be without the presence of these gases. Satellite observations of the radiation emitted from the Earth's surface and through the atmosphere confirm the effects of greenhouse gases. The composition of the atmospheres of Venus, the Earth and Mars are quite different but their surface temperatures are in general agreement with the principles of greenhouse effect. Finally, measurements from ice cores going back 160000 years show that the Earth 's temperature closely paralleled the amount of carbon dioxide and methane,

ome of the infra-redradiation is absorbedand re-emitted by thegreenhouse gases.The effect of this is twarm the surface andthe lower atmosphere

Some solar radiationis reflected by the earth

and the atmosphere

Most radiation is absorbedby the earth's surface

and warms it.

EARTHInfra-red radiation

is emitted fromthe earth's surface

Figure 2.1 - A simplified diagram of the greenhouse effect (Source:Houghton 1991).

two of the more important greenhouse gases in theatmosphere (Fig 2.2). The changes in the amounts of thesegases may be some, but not all, of the reason for the large (5-7°C) global temperature differences between the ice ages andthe interglacial periods (Houghton 1991). Recent studiesindicate that the temperatures and GHGs are so closelycorrelated that it is difficult to determine which is the causeand which is the effect.

16 Climate Change, Forests and Forest Management16 Climate Change, Forests and Forest Management

Some solar radiation is reflected by the earth

and the atmosphere

Most radiation is absorbed by the earth's surface

and warms it.

EARTH Infra-red radiation

is emitted from the earth's surface

Figure 2.1 - A simplified diagram of the greenhouse effect (Source: Houghton 1991).

two of the more important greenhouse gases in the atmosphere (Fig 2.2). The changes in the amounts of these gases may be some, but not all, of the reason for the large (5-7°C) global temperature differences between the ice ages and the interglacial periods (Houghton 1991). Recent studies indicate that the temperatures and GHGs are so closely correlated that it is difficult to determine which is the cause and which is the effect.


1990LEVELOF CO2

->'Ew aa

-5- z0H

z <Io F_ca zcC Lu<C)

Z00

300 -280 CARBON DIOXIDE260 -240220200 -

180 -

0 40Jill

80 120 160

-->'

700 Eo_o_

W z6 00 z 0

1<H1500 1-1-1 I---2 Z

LuOZ400 00

300280

260240220

200-180

AGE (THOUSAND YEARS BEFORE PRESENT)

Figure 2.2 - Analysis of air trapped in Antarctic ice cores shows thatmethane and carbon dioxide concentrations were closely correlatedwith average temperatures over the past 160 000 years (Watson etal 1990).

Climate Change, FDrests and Forest Management 17

UJ a: 2 ::J ~ t- U 0 <{ 0 a: --2 UJ UJ 0.. Cl - 4 ~ Z UJ <{ - 6 t- I --' > U -8 <{

- 10 700 E U 0

a. a.

--' METHANE 600 ~ is <{Itt-<{

500 ~ ~ UJ U

1990 LEVEL OF C02

400 is

>' E

UJa. o~ XZ go oi=

300 280 260

z <{ 240 o a: 220 220 cot-a: Z 200 200 <{UJ

U~ 100 180

8 0 40 80 120 1~ AGE (THOUSAND YEARS BEFORE PRESENT)

U

Figure 2.2 - Analysis of air trapped in Antarctic ice cores shows that methane and carbon dioxide concentrations were closely correlated with average temperatures over the past 160 000 years (Watson et al 1990).


6. WHICH GASES ARE CONSIDERED TO BE GHGS ANDWHAT ARE THE SOURCES OF THESE GASES?

Greenhouse gases (GHGs) present in the Earth's atmosphereinclude water vapour (H20), carbon dioxide (CO2), methane(CH4), nitrous oxide (N20), nitrogen oxides (NO.), ozone (03),carbon monoxide, (CO) and chlorofluorocarbons (CFC). Theconcentrations of these gases in the Earth's atmosphere havechanged over geological time scales. Since the last glacialperiod, the levels of these gases remained relatively constant.As agriculture and animal husbandry developed, the world'spopulation increased and human society became moreindustrialized, the levels of some of these gases increasedsignificantly (Houghton 1991). Descriptions of the importantGHGs and their sources are as follows:

WATER VAPOUR (F120) - Water vapour is the most abundantof the GHGs and has the largest greenhouse effect. Theamount of water vapour is only slightly affected by humanactivities such as irrigation and development of reservoirs.The amount of water vapour vvill increase if the atmospherebecomes warmer. Increased amounts of water vapour couldenhance the greenhouse effect.

CARBON DIOXIDE (CO2) - Carbon dioxide is the mostimportant of the GHGs influenced by human activity both interms of the amount in the atmosphere and potential effectson global warming. This gas is a product of respiration byanimals and plants, the burning of fossil fuels and the burningor decomposition of plants and trees. Cement factories areanother important source of CO, (IPCC 1992).

Since the beginning of the Industrial Revolution, in the mid18th century, the burning of fossil fuels has increased.Extensive deforestation and burning of debris has alsooccurred. These and other human activities have resulted inan increase in the concentration of carbon dioxide in theatmosphere by about 25% from 290 ppmv (parts per million


6. WHICH GASES ARE CONSIDERED TO BE GHGS AND WHA T ARE THE SOURCES OF THESE GASES?

Greenhouse gases (GHGs) present. in the Earth's atmosphere include water vapour (H20), carbon dioxide (C0 2 1. methane (CH.1. nitrous oxide (N 20), nitrogen oxides (NO,1. ozone (0 3),

carbon monoxide, (CO) and chlorofluorocarbons (CFC). The concentrations of these gases in the Earth's atmosphere have changed over geological time scales. Since the last glacial period, the levels of these gases remained relatively constant. As agriculture and animal husbandry developed, the world's population increased and human society became more industrialized, the levels of some of these gases increased significantly (Houghton 1991). Descriptions of the important GHGs and their sources are as follows:

WA TER VAPOUR (HP) - Water vapour is the most abundant of the GHGs and has the largest greenhouse effect. The amount of water vapour is only slightly affected by human activities such as irrigation and development of reservoirs. The amount of water vapour will increase if the atmosphere becomes warmer. Increased amounts of water vapour could enhance the greenhouse effect.

CARBON DIOXIDE (CO,! . Carbon dioxide is the most important of the GHGs influenced by human activity both in terms of the amount in the atmosphere and potential effects on global warming. This gas is a product of respiration by animals and plants, the burning of fossil fuels and the burning or decomposition of plants and trees. Cement factories are another important source of CO2 (lPCC 1992).

Since the beginning of the Industrial Revolution, in the mid 18th century, the burning of fossil fuels has increased. Extensive deforestation and burning of debris has also occurred. These and other human activities have resulted in an increase in the concentration of carbon dioxide in the atmosphere by about 25% from 290 ppmv (parts per million


by volume) to 355 ppmv at present. Most of this increase hastaken place since 1940 (Hair and Sampson 1992). Recentlya reduction in the rate of increase of atmospheric CO2 hasbeen detected (Sarimento 1993, see box 2.1).

METHANE (CH4) - The major source of methane is anaerobicdecomposition (decomposition by micro-organisms without thepresence of free oxygen in the air). This occurs in rice paddiesand natural wetlands. Methane is also a product of cattle andother ruminants, including wildlife whose digestive systemsrely on enteric fermentation. Another source of methane istermites, which are present in large numbers in tropical forests(Zimmerman et al 1982). Other sources include biomassburning and decomposition from landfills and wetlands. Forestfires emit one unit of methane for every 100 units of carbondioxide. The level of methane in the atmosphere has increasedfrom 0.8 ppmv in 1850 to 1.7 ppmv at present. Since 1970,for reasons unknown, the rate of increase of CH4 in the Earth'satmosphere has declined from about 20 ppbv/yr to as low as10 ppbv/yr (IPCC 1992).

NITROUS OXIDE (N20) - This gas is emitted as a result ofdeforestation and associated burning, biomass burning,intensification of soil nitrification and denitrification processesin intermittently wet areas, application of nitrogen fertilizersand combustion of fossil fuels.


by volume) to 355 ppmv at present. Most of this increase has taken place since 1940 (Hair and Sampson 1992). Recently a reduction in the rate of increase of atmospheric CO, has been detected (Sarimento 1993, see box 2.1).

METHANE (CH.) - The major source of methane is anaerobic decomposition (decomposition by micro-organisms without the presence of free oxygen in the air) . This occurs in rice paddies and natural wetlands . Methane is also a product of cattle and other ruminants, including wildlife whose digestive systems rely on enteric · fermentation. Another source of methane is termites, which are present in large numbers in tropical forests (Zimmerman et al 1982) . Other sources include biomass burning and decomposition from landfills and wetlands. Forest fires emit one unit of methane for every 100 units of carbon dioxide. The level of methane in the atmosphere has increased from 0 .8 ppmv in 1850 to 1.7 ppmv at present. Since 1970, for reasons unknown, the rate of increase of CH. in the Earth's atmosphere has declined f rom about 20 ppbvlyr to as low as 10 ppbv/yr (IPCC 1992).

NITROUS OXIDE (N,DJ - This gas is emitted as a result of deforestation and associated burning, biomass burning, intensification of soil nitrification and denitrification processes in intermittently wet areas, application of nitrogen fertilizers and combustion of fossil fuels .


Box 2.1. What happened to atmosphericCO2 levels in 1991 ?

According to data from the Mauna LoaObservatory in Hawaii, USA, a 35 yeartrend of steadily increasing levels ofatmospheric CO2 was broken beginning inmid-1991 when CO2 levels wereapproximately 355 ppmv. By late 1993, areduction of 1.5 parts per million (ppmv) ofatmospheric CO2 was detected. If this wereapplied to the entire northern hemisphere, itwould equate to a loss of 1.6 Gt (1.6 x 109tonnes) of carbon. This reduction in rate ofCO2buildup began shortly after the eruptionof the Philippine volcano, Mt. Pinatubo in1991 and occurred despite the fact that anENSO occurred during 1991-92. ENSOsnormally result in a temporary increase inatmospheric 002.

The cause of this phenomenon is notknown. Some scientists believe that anatural factor involving the oceans or theterrestrial biosphere is responsible. Onepossibility is that ash fallout, high in ironoxides, from the eruption of Mt. Pinatubocaused an iron fertilization of the oceanswhich temporarily increased their ability toabsorb CO2 (Sarimento 1993). If thePinatubo eruption is the main cause, thenthe slowdown should be short lived.


Box 2.1. What happened to atmospheric CO2 levels in 1991 ?

According to data from the Mauna Loa Observatory in Hawaii, USA, a 35 year trend of steadily increasing levels of atmospheric CO, was broken beginning in mid-1991 when CO, levels were approximately 355 ppmv. By late 1993, a reduction of 1.5 parts per million (ppmv) of atmospheric CO, was detected. If this were applied to the entire northern hemisphere, it would equate to a loss of 1.6 Gt (1.6 x 10' tonnes) of carbon. This reduction in rate of CO, buildup began shortly after the eruption of the Philippine volcano, Mt. Pinatubo in 1991 and occurred despite the fact that an EN SO occurred during 1991-92. ENSOs normally result in a temporary increase in atmospheric CO,.

The cause of this phenomenon is not known. Some scientists believe that a natural factor involving the oceans or the terrestrial biosphere is responsible. One possibility is that ash fallout. high in iron oxides, from the eruption of Mt. Pinatubo caused an iron fertilization of the oceans which temporarily increased their ability to absorb CO, (Sarimento 1993). If the Pinatubo eruption is the main cause, then the slowdown should be short lived.


Relatively little is presently known about the rates of releaseof this gas from soils in natural and disturbed ecosystems andfrom burning of biomass. The present level of N20 in theatmosphere is about 0.3 ppmv and is increasing at the rate of0.2 to 0.3% per year.

CARBON MONOXIDE (CO) - Carbon monoxide is not a trueGHG. However it influences the oxidizing capacity of theEarth's atmosphere and thus contributes to increasedconcentrations of methane and nitrous oxides. Burning ofsavanna grasslands as a form of livestock and pasturemanagement may be the largest single source because largequantities of CO are emitted as a result of incompletecombustion and smouldering rather than hot, rapid burning.

NITROGEN OXIDES (NO), SULPHUR DIOXIDE (SO2). OZONE(03) AND CHLOROFLUOROCARBONS (CFC-11 and CFC-12) -These GHGs are the result of non-biotic, industrial processessuch as the burning of fossil fuels, the chemical industry andcertain household appliances. Forestry and land use practicesare not sources of these GHGs.

Ozone is a gas which occurs throughout the atmospherealthough most of it resides in the stratosphere where it acts asa protective shield and prevents harmful ultraviolet (UV)radiation from reaching the Earth's surface. In the loweratmosphere (troposphere) 0.3 is formed as a result of lightningor as a component of photochemical smog. Exposure toelevated levels of tropospheric 03 can cause damage to plantsand be detrimental to human health. Certain varieties of beansand tobacco are known to be sensitive to elevated levels of03. Several species of trees can sustain injury as a result ofexposure to elevated levels of this gas (Jacobson and Hill1970).

CFCs, which were once used as aerosol propellants and arestill used in air conditioning systems promote the destructionof stratospheric 03 and contribute to its depletion. This is


Relatively little is presently known about the rates of release of this gas from soils in natural and disturbed ecosystems and from burning of biomass. The present level of N20 in the atmosphere is about 0.3 ppmv and is increasing at the rate of 0.2 to 0.3% per year.

CARBON MONOXIDE (CO) - Carbon monoxide is not a true GHG. However it influences the oxidizing capacity of the Earth's atmosphere and thus contributes to increased concentrations of methane and nitrous oxides. Burning of savanna grasslands as a form of livestock and pasture management may be the largest single source because large quantities of CO are emitted as a result of incomplete combustion and smouldering rather than hot, rapid burning.

NITROGEN OXIDES (NO), SULPHUR DIOXIDE (SO). OZONE (0) AND CHLOROFL UOROCARBONS (CFC-11 and CFC-12) -These GHGs are the result of non-biotic, industrial processes such as the burning of fossil fuels, the chemical industry and certain household appliances. Forestry and land use practices are not sources of these GHGs.

Ozone is a gas which occurs throughout the atmosphere although most of it resides in the stratosphere where it acts as a protective shield and prevents harmful ultraviolet (UV) radiation from reaching the Earth's surface. In the lower atmosphere (troposphere) 0 3 is formed as a result of lightning or as a component of photochemical smog. Exposure to elevated levels of tropospheric 0 3 can cause damage to plants and be detrimental to human health. Certain varieties of beans and tobacco are known to be sensitive to elevated levels of 0 3 , Several species of trees can sustain injury as a result of exposure to elevated levels of this gas (Jacobson and Hill 1970).

CFCs, which were once used as aerosol propellants and are still used in air conditioning systems promote the destruction of stratospheric 0 3 and contribute to its depletion. This is


believed to cause seasonal ozone holes to appear over thepolar regions.

WHAT IS THE SIGNIFICANCE OF HUMAN SOURCESOF GHGS?

Human activities are causing increases in the emissions ofsome GHGs into the atmosphere. Major human sources ofGHG emissions include the burning of fossil fuels,deforestation (and associated burning) to make additional landavailable for agriculture and grazing and the burning of woodand charcoal. Approximately 7 Gt of CO2 were released intothe atmosphere each year during the 1980s from humansources (see question 23). Approximately 75-80% of thisincrease is due to industrial sources. Most of the remainder isdue to deforestation and land use practices (Watson et al1990). Other sources of GHGs include paddy rice productionand animal husbandry. The latter two activities are sources ofmethane.

For over a century, scientists have warned that theseincreasing emissions may effect the atmosphere's radiativebalance leading to a significant and long-term increase in theEarth's temperature (Plass 1959, Hepting 1963).

DO ALL GHGS HA VE AN EQUAL WARMING EFFECT?

No; GHGs vary both in the time they are present in theatmosphere before they break down (residence times) and intheir radiative, or warming effect relative to carbon dioxide.Scientists have designated carbon dioxide the benchmark GHGagainst which the properties of all other GHGs are measured.In order to compare these gases, the concept of relative globalwarming potential (GWP) was developed as a means ofaccounting for differences in residence times and the radiativeeffects of GHGs (Table 2.1). Methane, for example, is a


believed to cause seasonal ozone holes to appear over the polar regions.

7. WHA T IS THE SIGNIFICANCE OF HUMAN SOURCES OFGHGS?

Human activities are causing increases in the emiSSions of some GHGs into the atmosphere. Major human sources of GHG emiSSions include the burning of fossil fuels, deforestation (and associated burning) to make additional land available for agriculture and grazing and the burning of wood and charcoal. Approximately 7 Gt of CO, were released into the atmosphere each year during the 1980s from human sources (see question 23) . Approximately 75-80% of this increase is due to industrial sources. Most of the remainder is due to deforestation and land use practices (Watson et al 1990). Other sources of GHGs include paddy rice production and animal husbandry. The latter two activities are sources of methane.

For over a century, scientists have warned that these increasing emissions may effect the atmosphere's radiative balance leading to a significant and long-term increase in the Earth's temperature (Plass 1959, Hepting 1963).

8. DO ALL GHGS HA VE AN EQUAL WARMING EFFECT?

No; GHGs vary both in the time they are present in the atmosphere before they break down (residence times) and in their radiative, or warming effect relative to carbon dioxide . Scientists have designated carbon dioxide the benchmark GHG against which the properties of all other GHGs are measured. In order to compare these gases, the concept of relative global warming potential (GWP) was developed as a means of accounting for differences in residence times and the radiative effects of GHGs (Table 2.1). Methane, for example, is a


relatively short-lived gas, consequently emissions from this gaswould have their greatest impacts on climate change duringthe first few decades after they are released. Nitrous oxideand CFCs, on the other hand, contribute to the greenhouseeffect for hundreds of years because they are more stable anddecompose very slowly in the atmosphere (IPCC 1992, 1994).

9. WHAT EVIDENCE EXISTS TO SUPPORT THE IDEATHAT GHG LEVELS IN THE ATMOSPHERE AREINCREASING?

There is strong evidence that the levels of several atmosphericGHGs have increased over the past 150 years.

In 1958, the first continuous CO2 monitoring programmesbegan at stations in Mauna Loa, Hawaii and Antarctica. Datafrom this monitoring clearly shows an annual increase in themean annual concentration of CO2. As of 1990, the globalmean value was 355 ppnnv. This is 25% above the 1850 valueof 280-290 ppmv (Fig 2.3) (Houghton 1991, Siegenthaler andSanhuezza 1991).

The concentration of methane in the atmosphere is presently1.7 ppmv, more than double the 1850 value. Ice coreanalyses show that levels of this gas remained fairly constantduring the 2000 years prior to industrialization. During the iceages, the concentration of methane in the atmosphere washalf of the present day level. Today's concentration of thisgas is higher than at any time in the past 150 000 years.

During the 1980s, the rates of methane increase declined,dropping from 16 ppbv/yr in 1980 to about 10 ppbv/yr by1990. Rates of methane buildup slowed dramatically in 1991and 1992 but there are indications that they increased againlate in 1993 (IPCC 1994).


relat ively short-lived gas, consequently emissions from this gas would have their greatest impacts on climate change during the fi rst few decades after they are released. Nitrous oxide and CFCs, on the other hand, contribute to the greenhouse effect for hundreds of years because they are more stable and decompose very slowly in the atmosphere (IPCC 1992, 1994) .

9. WHA T EVIDENCE EXISTS TO SUPPORT THE IDEA THA T GHG LEVELS IN THE A TMOSPHERE ARE INCREASING?

There is strong evidence that the levels of several atmospheric GHGs have increased over the past 150 years.

In 1958, the fi rst continuous CO 2 monitoring programmes began at stations in Mauna Loa, Hawaii and Antarctica. Data from this monitoring clearly shows an annual increase in the mean annual concentration of CO 2 • As of 1990, the global mean value was 355 ppmv. This is 25% above the 1850 value of 280-290 ppmv (Fig 2.3) (Houghton 1991 , Siegenthaler and Sanhuezza 1991).

The concentration of methane in the atmosphere is presently 1.7 ppmv, more than double the 1850 value. Ice core analyses show that levels of this gas remained fairly constant during the 2000 years prior to industrialization . During the ice ages, the concentration of methane in the atmosphere was half of the present day level. Today's concentration of this gas is higher than at any time in the past 1 50 000 years.

During the 1980s, the rates of methane increase declined , dropping from 16 ppbv/yr in 1980 to about 10 ppbv/yr by 1990. Rates of methane buildup slowed dramatically in 1991 and 1992 but there are indications that they increased again late in 1993 (lPCC 1994).


DIRECT GLOBAL WARMING POTENTIAL OF REPRESENTATIVEGREENHOUSE GASES FOR A 100 YEAR TIME HORIZON

(Source: IPCC 1992, 1 9 9 4)

360

350

340

330

320

310

300

290

280

2701700 1800

TABLE 2.1

Year1900 2000

Figure 2.3 - Changes in the levels of atmospheric CO2 over the past250 years as indicated by analysis of ice core data from theAntarctic and by atmospheric measurements at Mauna Loa, Hawaiisince 1958 (Source: Siegenthaler and Sanhuezza (1991)

GHG Global Warming PotentialRelative to Carbon Dioxide

CO2 1

CH4 11

N20 320CFC-1 1 4000CFC- 1 2 8 500HCFC-2 2 1 700HFC-1 34a 1 300


TABLE 2.1

DIRECT GLOBAL WARMING POTENTIAL OF REPRESENTATIVE GREENHOUSE GASES FOR A 100 YEAR TIME HORIZON

(Source: IPCC 1992, 1994)

GHG Global Warming Potential Relative to Carbon Dioxide

CO, 1 CH. 11 N,O 320 CFC-11 4000 CFC-12 8500 HCFC-22 1700 HFC-134a 1300

360c-------------------------------------~

350 ,;-~ 340 "-';; 330 o .~ 320

C 310 ~ u

5 300 u

0 290 (J

280 o 00

o 0

00 c Q::flJ CbocP o

0 0 d''''

0(JP goO'

) ;Po

270~~~~~~~~~~~~~~~~~~~ 1700 1800 1900 2000

Year

Figure 2.3 - Changes in the levels of atmospheric CO, over the past 250 years as indicated by analysis of ice core data from the Antarctic and by atmospheric measurements at Mauna Loa, Hawaii since 1958 (Source: Siegenthaler and Sanhuezza (1991)

Clima te Change, Forests and Forest Management 25

The present day concentration of nitrous oxides is about 0.31ppmv (parts per million by volume). This is 8% higher thanpre-industrial times. CFCs are exclusively of human origin andare recent components of the Earth's atmosphere. They havebeen studied intensively not only because of their greenhouseeffect but because they are depleting stratospheric ozone. In1990, the atmospheric concentration of the two mostimportant CFCs, CFC-11 and CFC-12 were 0.28 ppmv and0.48 ppmv respectively (Houghton 1990).

WHICH COUNTRIES PRESENTL Y MAKE THECREA TEST CONTRIBUTION TO ELEVA TED LEVELS OFGHGS?

The ten leading contributors of GHG emissions are the USA,the former USSR, Brazil, China, India, Japan, Germany, UK,Indonesia and France. Many of these countries have a largeindustrial and service sector and burn large volumes of fossilfuels (Watson et al 1990). Developing countries (includingChina and the former USSR) accounted for 36% of the globalenergy related carbon emissions in 1990. This represents anincrease from an estimated 28% in 1970 (GlobalEnvironmental Change Report 1994).

HOW CAN AEROSOLS COUNTERACT THE EFFECTSOF GHGS?

Aerosols consist of dust and other tiny particles which arereleased into the Earth's atmosphere. Many aerosols act asnuclei for the condensation of water droplets which make upclouds. Without condensation nuclei, clouds cannot form andrain could not occur.

There are numerous natural and human sources of aerosols.Dust from erupting volcanos or desert sand storms are two


The present day concentration of nitrous oxides is about 0.31 ppmv (parts per million by volume). This is 8% higher than pre-industrial times. CFCs are exclusively of human origin and are recent components of the Earth's atmosphere. They have been studied intensively not only because of their greenhouse effect but because they are depleting stratospheric ozone. In 1990, the atmospheric concentration of the two most important CFCs, CFC-11 and CFC-12 were 0.28 ppmv and 0.48 ppmv respectively (Houghton 1990).

10, WHICH COUNTRIES PRESENTLY MAKE THE GREA TEST CONTRIBUTION TO ELEVA TED LEVELS OF GHGS?

The ten leading contributors of GHG emissions are the USA, the former USSR, Brazil, China, India, Japan, Germany, UK, Indonesia and France. Many of these countries have a large industrial and service sector and burn large volumes of fossil fuels (Watson et al 1990). Developing countries (including China and the former USSR) accounted for 36% of the global energy related carbon emissions in 1990. This represents an increase from an estimated 28% in 1970 (Global Environmental Change Report 1994).

11. HOW CAN AEROSOLS COUNTERACT THE EFFECTS OFGHGS?

Aerosols consist of dust and other tiny particles which are released into the Earth's atmosphere. Many aerosols act as nuclei for the condensation of water droplets which make up clouds . Without condensation nuclei. clouds cannot form and rain could not occur.

There are numerous natural and human sources of aerosols. Dust from erupting volcanos or desert sand storms are two


examples of natural sources. The black soot produced byforest, savanna and rangeland fires can be either a natural orhuman source depending on the cause of the fire. The mostsignificant human source of aerosols is the emission ofsulphates from power generating stations which can causeacid rain (IPCC 1994).

Aerosols may counteract the warming effect caused byelevated levels of GHGs. They help to cool the atmosphere intwo ways. The primary effect is to scatter sunlight, reducingthe amount that reaches the Earth's surface. An increase inthe level of aerosols can alter the density and consequentlythe reflectance of clouds and cause a cooling effect. There isevidence from Australia, the United States and countries ofthe former USSR that the amount of cloud cover over theseregions has increased. Consequently, some climatologistspredict that some areas of the world may actually experiencea cooling effect in the future (Pearce 1994).


examples of natural sources. The black soot produced by forest, savanna and rangeland fires can be either a natural or human source depending on the cause of the fire. The most significant human source of aerosols is the emission of sulphates from power generating stations which can cause acid ra in ((PCC 1994).

Aerosols may counteract the warming effect caused by elevated levels of GHGs. They help to cool the atmosphere in two ways. The primary effect is to scatter sunlight, reducing the amount that reaches the Earth's surface. An increase in the level of aerosols can alter the density and consequently the reflectance of clouds and cause a cooling effect. There is evidence from Australia, the United States and countries of the former USSR that the amount of cloud cover over these regions has increased . Consequently, some climatologists predict that some areas of the world may actually experience a cooling effect in the future (Pearce 1994).


Chapter 3PREDICTED CHANGES IN THE EARTH'S

CLIMATE AND EXPECTED EFFECTS

IN GENERAL, WHAT ARE THE PREDICTED EFFECTSOF INCREASED LEVELS OF GHGS ON THE EARTH'SCLIMA TE?

Increases in atmospheric levels of CO2 and other GHGs canhave far reaching effects. They include increases in averagetemperatures and changes in precipitation, numbers of frostfree days and the frequency and severity of storms (seequestion 15). There is also a likelihood that ocean levels mayrise (see question 17).

Green plants utilize CO2 during photosynthesis. Consequentlyincreased levels of GHGs can have potentially significanteffects on the growth and survival of green plants, includingtrees (see question 18). In addition, changes in climate couldeffect the distribution of animals and plants (see questions 33and 34) and the processes involved in soil formation (seequestion 19). These effects could have serious implications inthe future for agriculture, fisheries and forestry.

HOW ARE CHA NGES IN THE EARTH'S CLIMATEPREDICTED?

The general circulation model or GCM is the most highlydeveloped tool available with which to predict changes in thefuture world's climate. At least 12 different GCMs are now inuse. These are based on the laws of physics and usedescriptions of natural processes such as cloud developmentand deep mixing in the oceans. In the most recent GCMs, anatmospheric component, essentially the same as a weather


Chapter 3 PREDICTED CHANGES IN THE EARTH'S

CLIMATE AND EXPECTED EFFECTS

12. IN GENERAL, WHA T ARE THE PREDICTED EFFECTS OF INCREASED LEVELS OF GHGS ON THE EARTH'S CLIMATE?

Increases in ' atmospheric levels of CO2 and other GHGs can have far reaching effects. They include increases in average temperatures and changes in precipitation, numbers of frost free days and the frequency and severity of storms (see question 15). There is also a likelihood that ocean levels may rise (see question 17).

Green plants utilize CO2 during photosynthesis. Consequently increased levels of GHGs can have potentially significant effects on the growth and survival of green plants, including trees (see question 18). In addition, changes in climate could effect the distribution of animals and plants (see questions 33 and 34) and the processes involved in soil formation (see question 19). These effects could have serious implications in the future for agriculture, fisheries and forestry.

13. HOW ARE CHANGES IN THE EARTH'S CLIMATE PREDICTED?

The general circulation model or GCM is the most highly developed tool available with which to predict changes in the future world's climate. At least 12 different GCMs are now in use. These are based on the laws of physics and use descriptions of natural processes such as cloud development and deep mixing in the oceans. In the most recent GCMs, an atmospheric component, essentially the same as a weather


prediction model, is coupled to a model of the ocean. Someof the more widely used GCMs are:

GISS - Goddard Institute of SpaceSciences

NCAR - National Center for AtmosphericResearch

UKLO, UKHI - UK Meteorological Office

GFLO, GFHI - Geophysical Fluid DynamicsLaboratory

CCC - Canadian Climate Centre

To make a forecast of future climate, the model is first runover a simulated period of a few decades with no changes inthe present atmospheric levels of GHGs. The statistical outputis a description of the model's predicted climate which, if themodel is a good one, will bear a close resemblance to today'sclimatic conditions. The exercise is then repeated with a newset of atmospheric conditions (e.g. the equivalent of adoubling of CO2 levels, see question 8, Table 2.1). Thedifferences between the outputs of the two simulations (e.g.mean temperature or inter-annual variability) provide anestimate of climate change (Fig 3.1). The long term change insurface air temperature following a doubling of carbon dioxideis used as a standard to compare predictions by differentGCMs. The outputs are different between models which takean immediate doubling of CO2 as a starting point whencompared to transient models which apply more gradualincreases in CO2 concentrations.


prediction model, is coupled to a model of the ocean. Some of the more widely used GCMs are:

GISS -

NCAR-

UKLO, UKHI-

GFLO, GFHI-

CCC -

Goddard Institute of Space Sciences

National Center for Atmospheric Research

UK Meteorological Office

Geophysical Fluid Dynamics Laboratory

Canadian Climate Centre

To make a forecast of future climate, the model ;s first run over a simulated period of a few decades with no changes in the present atmospheric levels of GHGs. The statistical output is a description of the model's predicted climate which, if the model is a good one, will bear a close resemblance to today's climatic conditions. The exercise is then repeated with a new set of atmospheric conditions (e.g . the equivalent of a doubling of CO, levels, see question 8, Table 2.1). The differences between the outputs of the two simulations (e.g. mean temperature or inter-annual variability) provide an estimate of climate change (Fig 3.1). The long term change in surface air temperature following a doubling of carbon dioxide is used as a standard to compare predictions by different GCMs. The outputs are different between models which take an immediate doubling of CO, as a starting point when compared to transient models which apply more gradual increases in CO, concentrations.


c) DF 2 X 002 - X CO2 PRECIPtTATION: UKHI

-----_____ ,,': -¡------ ,- ----_,----,---;1--- :

--

(f) JJA 2 X CO2 - 1 X CO2 PRECIFTATION: UKHI .

....bor

- 0)

Figure 3.1 - An example of a prediction of global change inprecipitation for winter (top) and spring (bottom) produced by theUKHI GCM. Areas of decrease are stippled.


\e} DJF 2 X CO2· , X CO2 PRECIPITATION: UKHI

In JJA 2 X CO2., X C02 PRECIPrrATION, UKHI,

Figure 3.1 - An example of a prediction of global change in precipitation for winter (top) and spring (bottom) produced by the UKHI GeM. Areas of decrease are stippled.


Another approach to predicting future climate change is tosearch for periods in the Earth's past when global meantemperatures were similar to those at present or expected inthe future. It is necessary for factors such as greenhouse gaslevels, orbital variations, and other conditions such as icecover and topography to be similar in order to get a goodprediction using this approach. Periods in the Earth's historywith levels of GHGs which are similar to today's or predictedfor the next 100-200 years have not yet been found(Houghton 1991).

14. HOW RELIABLE ARE PRESENT PREDICTIONS OFCLIMA TE CHANGE?

Predictions of climate change are uncertain because of ourimperfect knowledge of future rates of emissions, the climaticresponse to these changes and of weaknesses inherent in themodels used to forecast climate change.

Future climate changes will depend, among other factors, onthe rate at which GHGs are emitted (see question 9). This willbe influenced by a number of inter-related socio-economicfactors. In addition, because of our imperfect level ofknowledge of the sources and sinks of GHGs, there areuncertainties in the calculations of future concentrationsarising from any emissions scenario entered into a GCM.Because natural sources and sinks of GHGs are themselvessensitive to changing climate, they could substantially modifyfuture concentrations. For example, if wetlands were tobecome warmer, methane emissions could increase. If theywere to become drier, more methane would be absorbed.There are also important processes in the oceans which caneffect GHG concentrations (see question 4).

The models used to predict climate change are only as good asour understanding of the processes which affect climate.Presently this is far from perfect. The range of variability of


Another approach to predicting future climate change is to search for periods in the Earth's past when global mean temperatures were similar to those at present or expected in the future . It is necessary for factors such as greenhouse gas levels, orbital variations, and other conditions such as ice cover and topography to be similar in order to get a good prediction using this approach . Periods in the Earth's history with levels of GHGs which are similar to today's or predicted for the next 100-200 years have not yet been found (Houghton 1991) .

14, HOW RELIABLE ARE PRESENT PREDICTIONS OF CLlMA TE CHANGE?

Predictions of climate change are uncertain because of our imperfect knowledge of future rates of emissions, the climatic response to these changes and of weaknesses inherent in the models used to forecast climate change .

Future climate changes will depend, among other factors , on the rate at which GHGs are emitted (see question 9). This will be influenced by a number of inter-related socio-economic factors. In addition, because of our imperfect level of knowledge of the sources and sinks of GHGs, there are uncertainties in the calculations of future concentrations arising from any emissions scenario entered into a GeM. Because natural sources and sinks of GHGs are themselves sensitive to changing climate, they could substantially modify future concentrations . For example, if wetlands were to become warmer, methane emissions could increase. If they were to become drier, more methane would be absorbed. There are also important processes in the oceans which can effect GHG concentrations (see question 4).

The models used to predict climate change are only as good as our understanding of the processes which affect climate. Presently this is far from perfect. The range of variability of


climate predictions by different GCMs reflects modelimperfections. The largest of these uncertainties is ourunderstanding of the factors which affect cloud abundanceand distribution and the interaction of clouds with solarradiation. Other uncertainties arise from the transfer of energybetween the atmosphere and the ocean, the atmosphere andland surfaces, and between the various layers in the ocean(Maunder 1990).

Another point to keep in mind is that present GCMs describethe climate for an equilibrium situation (eg the situation arisingfrom a doubling of CO2 concentration in the atmosphere).They give no indication of how this equilibrium will be reachedor how much time will be required to reach it.

15. WHAT CHANGES IN CLIMA TE ARE PREDICTED WITHA DOUBLING OF CO2 FROM PRE-INDUSTRIALREVOLUTION LEVELS?

Based on outputs of several GCMs; temperatures are expectedto rise, precipitation will generally increase, the climate maybecome more variable and there could be an increase inincidence of tropical storms. These changes are discussed inmore detail in the following paragraphs.

TEMPERATURE - GCMs predict a range of temperatureincrease between 1.5 to 4.5°C with a doubling of CO2equivalents from level present during the middle of the 19thcentury. This is expected to occur at the rate of 0.3°C ( ±0.2-0.5') per decade during the next century and could resultin a temperature increase of 1°C above present day levels bythe year 2025 and of 2°C before the end of the next century(Houghton 1991). According to some scientists, this rate ofchange is unprecedented in geologic history.


climate predictions by different GCMs reflects model imperfections. The largest of these uncertainties is our understanding of the factors which affect cloud abundance and distribution and the interaction of clouds with solar radiation. Other uncertainties arise from the transfer of energy between the atmosphere and the ocean, the atmosphere and land surfaces, and between the various layers in the ocean (Ma under 1990).

Another point to keep in mind is that present GCMs describe the climate for an equilibrium situation (eg the situation arising from a doubling of CO, concentration in the atmosphere). They give no indication of how this equilibrium will be reached or how much time will be required to reach it.

15. WHA T CHANGES IN CLlMA TE ARE PREDICTED WITH A DOUBLING OF CO, FROM PRE-INDUSTRIAL REVOLUTION LEVELS?

Based on outputs of several GCMs; temperatures are expected to rise, precipitation will generally increase, the climate may become more variable and there could be an increase in incidence of tropical storms. These changes are discussed in more detail in the following paragraphs.

TEMPERA TURE - GCMs predict a range of temperature increase between 1.5 to 4 .5°C with a doubling of CO, equivalents from level present during the middle of the 19th century. This is expected to occur at the rate of O. 3°C (± 0.2-0.5°) per decade during the next century and could result in a temperature increase of 1°C above present day levels by the year 2025 and of 2°C before the end of the next century (Houghton 1991). According to some scientists, this rate of change is unprecedented in geologic history.


PRECIPITATION - Increased warming of the Earth's surfacewill lead to increased evaporation and greater average globalprecipitation. However, some regions may have reducedrainfall. High latitude regions are expected to experienceincreased movement of warm moist air toward the poles,leading to increased annual precipitation and river runoff.Existing GCMs give widely different estimates of newgeographic patterns of precipitation/evaporation ratios.

CLIMA TIC VARIABILITY - Changes in the variability of weatherand the frequency of extreme climatic events will generallyhave more impact than changes in the average conditions.However, with the possible exception of an increase in thenumber of intense showers, there is no clear evidence thatweather variability will change in the future. Assuming nochange in temperature range, but a modest increase in theaverage temperature, the number of days with very hightemperatures could increase substantially. There could also bea decrease in days with very cold temperatures. Consequentlythe number of very hot or cold days could change substantiallywithout changes in the variability of the weather. The numberof days with a minimum threshold amount of soil moisturerequired for certain crops could be affected by changes inaverage precipitation (Houghton 1991).

STORMS - Tropical storms such as typhoons and hurricanesdevelop when ocean surface temperatures are in excess of26°C. Higher ocean surface temperatures could thereforeresult in an increase in tropical storms and resultant damageincluding damage to forest resources (Fig 3.2). While systemsare available to forecast storms in advance (Gray 1993),present day GCMs are unable to make such predictions.Consequently there is a great deal of uncertainty presentlyassociated with the effects of climate change on storm events(Houghton 1991).


PRECIPITA TlON - Increased warming of the Earth's surface will lead to increased evaporation and greater average global precipitation. However, some regions may have reduced rainfall. High latitude regions are expected to experience increased movement of warm moist air toward the poles, leading to increased annual precipitation and river runoff. Existing GCMs give widely different estimates of new geographic patterns of precipitationlevaporation ratios.

CLlMA TIC VARIABILITY - Changes in the variability of weather and the frequency of extreme climatic events will generally have more impact than changes in the average conditions. However, with the possible exception of an increase in the number of intense showers, there is no clear evidence that weather variability will change in the future. Assuming no change in temperature range, but a modest increase in the average temperature, the number of days with very high temperatures could increase substantially. There could also be a decrease in days with very cold temperatures. Consequently the number of very hot or cold days could change substantially without changes in the variability of the weather. The number of days with a minimum threshold amount of soil moisture required for certain crops could be affected by changes in average precipitation (Houghton 1991).

STORMS - Tropical storms such as typhoons and hurricanes develop when ocean surface temperatures are in excess of 26°C. Higher ocean surface temperatures could therefore result in an increase in tropical storms and resultant damage including damage to forest resources (Fig 3.2). While systems are available to forecast storms in advance (Gray 1993). present day GCMs are unable to make such predictions. Consequently there is a great deal of uncertainty presently associated with the effects of climate change on storm events (Houghton 1991).


16. IS THE CLIMA TE OF SOME REGIONS OF THE WORLDEXPECTED TO CHA NGE TO A CREA TER DEGREETHAN OTHERS?

Yes; there is general agreement among GCMs that there couldbe a broad latitudinal climate response due to an increasedgreenhouse effect. Warming could be much greater in thehigh latitudes and much less toward the equator. The mostextreme temperature increases are likely to occur in winter inthe high latitude of the northern hemisphere where changescould be a much as 2 1/2 times greater than the globalaverage. The least amount of change is predicted to occur inthe tropics.

Predictions of regional changes in climate are less clear. Onestudy, which compares the predictions of severa! GCMs,indicates increased evaporation leading to increased summerdryness in mid-latitude continental interiors. Many of theseregions are of great agricultural importance (Easterling 1990).

-

g: 1

tr.

4h-!

\ 1.1 viol; .3440

Figure 3.2 - Increases in the number of tropical storms, which candamage many resources including forests, are a possible, butuncertain outcome of global climate change.


16. IS THE CL/MA TE OF SOME REGIONS OF THE WORLD EXPECTED TO CHANGE TO A GREA TER DEGREE THAN OTHERS?

Yes; there is general agreement among GCMs that there could be a broad latitudinal climate response due to an increased greenhouse effect. Warming could be much greater in the high latitudes and much less toward the equator. The most extreme temperature increases are likely to occur in winter in the high latitude of the northern hemisphere where changes could be a much as 2 1/2 times greater than the global average. The least amount of change is predicted to occur in the tropics.

Predictions of regional changes in climate are less clear. One study, which compares the predictions of several GCMs, indicates increased evaporation leading to increased summer dryness in mid-latitude continental interiors. Many of these regions are of great agricultural importance (Easterling 1990).

Figure 3.2 - Increases in the number of tropical storms, which can damage many resources including forests, are a possible, but uncertain outcome of global climate change.


WHAT CHANGES IN THE LEVEL OF THE OCEANS AREEXPECTED DUE TO CLIMA TE CHANGE?

An overall rise in sea level is predicted. This is based on theassumption that current rates of increase in the levels of GHGscontinue as predicted. By 2100, a rise in ocean levels of 60cm is expected. This is largely due to thermal expansion ofthe surface waters of the oceans. This could have severeeffects on small island nations, countries with large areas oflow lying coastal plains and where large population centres areconcentrated in coastal regions.

A rise in the ocean level is not expected to be uniform over theentire globe. Thermal expansion, changes in ocean circulationand surface air pressure will vary from region to region as theclimate changes. The magnitude of these changes is not yetknown.

The most severe effects of sea level rise are likely to resultfrom extreme climatic events, such as storm surges, theincidence of which could also be affected by a changingclimate (Houghton 1991). This, however, is one of the lesscertain predictions of the effects of global climate change.

HOW WILL PLANTS, INCLUDING TREES, BEINFLUENCED BY CHA NGES IN THE LEVELS OF GHGsIN THE EARTH'S ATMOSPHERE AND RESULTANTCHANGES IN TEMPERA TURE AND PRECIPITATION ?

The changes in levels of GHGs in the Earth's atmosphere andexpected changes in climate can have both positive andnegative effects on plants.

One of the potential positive effects of increased levels ofatmospheric CO2 is known as the "CO2 fertilization effect". Itis known that CO2 is a limiting factor in plant growth.Increased atmospheric CO2 allows more photosynthesis by


17. WHA T CHANGES IN THE LEVEL OF THE OCEANS ARE EXPECTED DUE TO CL/MA TE CHANGE?

An overall rise in sea level is predicted . This is based on the assumption that current rates of increase in the levels of GHGs continue as predicted. By 2100, a rise in ocean levels of 60 cm is expected. This is largely due to thermal expansion of the surface waters of the oceans. This could have severe effects on small island nations, countries with large areas of low lying coastal plains and where large population centres are concentrated in coastal regions.

A rise in the ocean level is not expected to be uniform over the entire globe. Thermal expansion, changes in ocean circulation and surface air pressure will vary from region to region as the climate changes. The magnitude of these changes is not yet known.

The most severe effects of sea level rise are likely to result from extreme climatic events, such as storm surges, the incidence of which could also be affected by a changing climate (Houghton 19911. This, however, is one of the less certain predictions of the effects of global climate change.

18. HOW WILL PLANTS, INCLUDING TREES, BE INFLUENCED BY CHANGES IN THE LEVELS OF GHGs IN THE EARTH'S A TMOSPHERE AND RESUL TANT CHANGES IN TEMPERA TURE AND PRECIPITA TlON ?

The changes in levels of GHGs in the Earth's atmosphere and expected changes in climc:te can have both positive and negative effects on plants.

One of the potential positive effects of increased levels of atmospheric CO 2 is known as the "C0 2 fertilization effect". It is known that CO 2 is a limiting factor in plant growth. Increased atmospheric CO 2 allows more photosynthesis by


plants, resulting in at least a temporarily higher growth rateand rate of removal of atmospheric carbon by plants, providedthat other requirements for plant growth are satisfied.Laboratory and field experiments indicate an increase inphotosynthesis of about 30% in plants which use the C3photosynthesis process with increasing root/shoot ratiosimplying more underground storage of carbon 2. An increasein the rate of photosynthesis of about 10% is expected inplants which use the C4 process. It is likely that the gradualincrease in atmospheric CO2 over the past century hascontributed partially to the approximate doubling of agriculturalproduction worldwide which has been achieved largely throughimproved farming practices and genetic improvement of plantmaterials over the same period. Research trials indicate thatthis fertilizing effect would be most effective in the lowerranges of the CO2 increase.

Related to the fertilizing, effect is the fact that plants contracttheir stomatal openings at higher levels of atmospheric CO2.This results in less water vapour loss and an increase in theplant's water use efficiency. This implies that increased plantgrowth may be possible in regions of the world where there islow precipitation. A study of the possible effects of higherwater use efficiency by plants, combined with the CO2fertilization effect, indicates that the area where tropicalrainforests could grow might increase by 75% with a doublingof atmospheric CO2 and the area of deserts could shrink by60% (Sombroek 1991).

2Most plants assimilate carbon by one of two photosynthetic pathways.

These are commonly referred to as the C., and C4 pathways. During the first stagesof CO2 absorption, C3 plants manufacture a molecule with three carbon atoms and C4plants manufacture a four atom molecule. The C4 molecule enables the plant toassimilate CO, more efficiently. C, plants depend on simple diffusion of CO2 throughtheir tissue and therefore benefit more than C4 plants froirn higher CO, concentrations.Plants possessing the C3 pathway account for 85% of all plant species and includeall trees and woody plants. Plants with the C4 pathway are tropical and temperategrasses which grow in areas of abundant warm season precipitation. Sugar cane,maize, sorghum and millet are all C4 plants.


plants, resulting in at least a temporarily higher growth rate and rate of removal of atmospheric carbon by plants, provided that other requirements for plant growth are satisfied. Laboratory and field experiments indicate an increase in photosynthesis of about 30% in plants which use the C3

photosynthesis process with increasing root/shoot ratios implying more underground storage of carbon 2. An increase in the rate of photosynthesis of about 10% is expected in plants which use the C. process. It is likely that the gradual increase in atmospheric CO 2 over the past century has contributed partially to the approximate doubling of agricultural production worldwide which has been achieved largely through improved farming practices and genetic improvement of plant materials over the same period. Research trials indicate that this fertilizing effect would be most effective in the lower ranges of the CO2 increase.

Related to the fertilizing. effect is the fact that plants contract their stomatal openings at higher levels of atmospheric CO2 ,

This results in less water vapour loss and an increase in the plant's water use efficiency. This implies that increased plant growth may be possible in regions of the world where there is low precipitation. A study of the possible effects of higher water use efficiency by plants, combined with the CO 2

fertilization effect, indicates that the area where tropical rainforests could grow might increase by 75% with a doubling of atmospheric CO2 and the area of deserts could shrink by 60% (Sombroek 1991).

2 Most plants assimilate carbon by one of two photosynthetic pathways.

These are commonly referred to as the c; and C4 pathways. During the first stages of CO2 absorption, C3 plants manufacture a molecule with three carbon atoms and C. plants manufacture 8 four atom molecule. The C. molecule enables the plant to assimilate CO2 more efficiently. C3 plants depend on simple diffusion of CO 2 through their tissue and therefore benefit more than C. plants Iro(11 higher CO 2 concentrations. Plants possessing the C3 pathway account for 85% of all plant species and include all trees and woody plants. Plants with the C. pathway are tropical and temperata grasses which grow in areas of abundant warm season precipitation. Sugar cane, maize, sorghum and millet are all C4 plants .


A higher global temperature implies a degree of increase inplant production, especially in high latitudes where thetemperature rise would be proportionally greater according tothe predictions of all GCMs.

Potential negative effects of changes in temperature andprecipitation on plants include (FAO 1990):

High daily temperatures, even of a few hoursduration, can cause pollen sterility in somecrops such as rice and wheat.

Increased cloud cover and precipitation in someregions could result in reduced yields of manycrops. Rice yields, for example, can be 1 to 2tonnes less per hectare in rainy seasons than indry seasons when grown under the sameconditions.

Areas with present day Mediterranean climates(mild, wet winters and hot dry summers) arepredicted to become drier resulting in reducedsoil moisture, especially during the growingseasons. This would result in reduced cropproduction, reduced growth rates in forests andincreased risk of wildfires.

The same conditions which result in increasedcrop yields will also favour weeds, enablingthem to be more competitive with crops.

Increased temperatures could cause pests anddiseases to extend their ranges, particularlynorthward and into tropical highland regions.Survival of overwintering populations could behigher and breeding cycles shorter withconsequent increases in the frequency andintensity of outbreaks.


A higher global temperature implies a degree of increase in plant production, especially in high latitudes where the temperature rise would be proportionally greater according to the predictions of all GeMs.

Potential negative effects of changes in temperature and precipitation on plants include (FAO 1990):

•

•

•

•

•

High daily temperatures, even of a few hours duration, can cause pollen sterility in some crops such as rice and wheat.

Increased cloud cover and precipitation in some regions could result in reduced yields of many crops. Rice yields, for example, can be 1 to 2 tonnes less per hectare in rainy seasons than in dry seasons when grown under the same conditions.

Areas with present day Mediterranean climates (mild, wet winters and hot dry summers) are predicted to become drier resulting in reduced soil moisture, especially during the growing seasons. This would result in reduced crop production, reduced growth rates in forests and increased risk of wildfires.

The same conditions which result in increased crop yields will also favour weeds, enabling them to be more competitive with crops.

Increased temperatures could cause pests and diseases to extend their ranges, particularly northward and into tropical highland regions. Survival of overwintering populations could be higher and breeding cycles shorter with consequent increases in the frequency and intensity of outbreaks.


The areas where certain agricultural crops andtree species can grow may shift. One studyindicates that climate change could result in ashift of several hundred kilometres of the NorthAmerican corn belt from the Southwest to theNortheast (Easterling 1990). Depending onlocation, this could be both a positive andnegative effect.

19. HOW MIGHT SOILS BE AFFECTED BY CHANGES INCLIMA TE?

Changing temperatures can alter the rate of microbial activityin soils. If temperatures increase, the rate of microbial activitywill increase proportionally. This will cause organic matter tobreak down at faster rates, which in turn will accelerate therate of CO2 release. The amount of carbon stored in soils isestimated to be almost twice that in the atmosphere (seequestion 20). Consequently, a small increase in the rate ofmicrobial activity can be expected to make a significantcontribution to amount of CO2 in the atmosphere. Some soilsare also sources of NO and CH,.

Breakdown of organic matter in soils results in a release ofnitrogen and makes it available for plant growth. The rate ofchemical weathering of mineral soil is also expected toincrease with increased temperatures, making additionalnutrients available for plant growth. Increased availability ofsoil nutrients could contribute to accelerated plant growth(Grace 1991).


• The areas where certain agricultural crops and tree species can grow may shift. One study indicates that climate change could result in a shift of several hundred kilometres of the North American corn belt from the Southwest to the Northeast (Easterling 1990). Depending on location, this could be both a positive and negative effect .

19. HOW MIGHT SOILS BE AFFECTED BY CHANGES IN CLIMATE?

Changing temperatures can alter the rate of microbial activity in soils. If temperatures increase, the rate of microbial activity will increase proportionally. This will cause organic matter to break down at faster rates, which in turn will accelerate the rate of CO2 release. The amount of carbon stored in soils is estimated to be almost twice that in the atmosphere (see question 20). Consequently, a small increase in the rate of microbial activity can be expected to make a significant contribution to amount of CO2 in the atmosphere. Some soils are also sources of NO. and CH •.

Breakdown of organic matter in soils results in a release of nitrogen and makes it available for plant growth. The rate of chemical weathering of mineral soil is also expected to increase with increased temperatures, making additional nutrients available for plant growth. Increased availability of soil nutrients could contribute to accelerated plant growth (Grace 1991).


20. IS THERE ANY EVIDENCE WHICH INDICA TES THATCLIMA TE CHANGES MA Y HA VE ALREAD YOCCURRED DUE TO INCREASES IN GHG LEVELS?

In 1988, a drought occurred over the central portions of NorthAmerica resulting in massive crop failures. This raisedspeculation among scientists and the general public that thisdrought was the result of an increased greenhouse effect.More recent climatic events, such as a drought over much ofeastern and southern Africa which began during the1991/1992 season and affected nearly 100 million people(Cane et al 1994), several severe hurricanes which batteredthe east coast of North America, the major flooding whichoccurred in the Mississippi and Missouri River Basins of theUnited States in 1993, and record high temperatures in Europeand North America in the early 1990s could also lead one tobelieve that the Earth is beginning to feel the effects of climatechange.

Most climatologists insist however that there is not enoughinformation to determine if these events are due to a changingclimate or are part of normal climatic variation. Droughts,floods and severe storms have always affected humansocieties. At least one study indicates that the features of theNorth American drought of 1988 were consistent withdroughts which occurred earlier this century. This wouldsuggest that there is nothing new or particularly surprisingabout this drought. In fact, precipitation over the past decadein the Midwestern United States has been above normal,particularly during the summer, a trend contrary to that whichsome GCMs predict for an increased greenhouse response inthis region (Easterling 1990). In addition, in 1988, the year ofthe North American drought, precipitation in the Sahel regionof West Africa began to return to normal levels after a droughtwhich lasted over 25 years (Gommes 1993).


20, IS THERE ANY EVIDENCE WHICH INDICA TES THA T CLIMATE CHANGES MAY HAVE ALREADY OCCURRED DUE TO INCREASES IN GHG LEVELS?

In 1988, a dreught .occurred ever the central pertiens .of Nerth America resulting in massive crep failures. This raised speculatien ameng scientists and the general public that this dreught was the result .of an increased greenheuse effect. Mere recent climatic events, such as a dreught ever much .of eastern and seuthern Africa which began during the 1991/1992 seasen and affected nearly 100 millien peeple (Cane et al 1994)' several severe hurricanes which battered the east ceast .of Nerth America, the majer fleeding which .occurred in the Mississippi and Misseuri River Basins .of the United States in 1993, and recerd high temperatures in Eurepe and Nerth America in the early 1 990s ceuld alse lead .one t.o believe that the Earth is beginning te feel the effects .of climate change.

Mest climatelegists insist hewever that there is net eneugh infermatien te determine if these events are due te a changing climate er are part .of normal climatic variatien. Dreughts, fleeds and severe sterms have always affected human secieties. At least .one study indicates that the features .of the Nerth American dreught .of 1988 were censistent with dreughts which .occurred earlier this century. This weuld suggest that there is nething newer particularly surprising abeut this dreught. In fact, precipitatien ever the past decade in the Midwestern United States has been abeve nermal, particularly during the summer, a trend centrary te that which seme GCMs predict fer an increased greenheuse respense in this regien (Easterling 1990). In additien, in 1988, the year .of the Nerth American dreught, precipitatien in the Sahel regien .of West A frica began te return te nermal levels after a dreught which lasted ever 25 years (Gemmes 1993).


Another complicating factor is that human populations haveincreased significantly over the past two to three decades.Consequently when climatic anomalies such as droughtsoccur, more people are affected. High human populationdensities also lead to less resilient agricultural productionsystems. This amplifies climatic anomalies. Land degradation,cultivation of marginal lands with low natural fertility or waterholding capacity and shorter fallow periods can exacerbatedrought conditions (Gommes 1993). This is especially true ofregions such as Sudo-Sahelian Africa and northeastern Brazilwhich have been historically prone to drought events.

The average global temperature has shown a gradual increaseof 0.3 to 0.5 °C since the 1850s. However this trend is somasked by annual and regional variations that it is virtuallyimpossible to attribute the increase to a specific cause.


Another complicating factor is that human populations have increased significantly over the past two to three decades. Consequently when climatic anomalies such as droughts occur, more people are affected. High human population densities also lead to less resilient agricultural production systems. This amplifies climatic anomalies. Land degradation, cultivation of marginal lands with low natural fertility or water holding capacity and shorter fallow periods can exacerbate drought conditions (Gommes 1993). This is especially true of regions such as Sudo-Sahelian Africa and northeastern Brazil which have been historically prone to drought events.

The average global temperature has shown a gradual increase of 0.3 to 0.5 °C since the 1850s. However this trend is so masked by annual and regional variations that it is virtually impossible to attribute the increase to a specific cause.


Chapter 4THE GLOBAL CARBON CYCLE

21, WHAT PROCESSES EXIST FOR THE EXCHANGE OFCARBON BETWEEN THE ATMOSPHERE, THE OCEANSAND THE LAND?

There is a finite but extremely large amount of carbon on theEarth (Table 4.1). Carbon occurs in the ocean, in soils, fossilcarbon reserves, bedrock, the atmosphere and plant biomass.The carbon cycle is the movement of carbon, in its variousforms, between the Earth's surface, its interior andatmosphere. The major pathways of the exchange of carbonare photo-synthesis, respiration and oxidation. Movementoccurs between living organisms, the atmosphere, the landand water (Fig 4.1). Over the course of millions of years, thecarbon cycle has concentrated large amounts of carbon inbedrock, primarily as limestone and in fossil fuels.

The carbon cycle is thought of as four interconnectedreservoirs or pools; the atmosphere, the terrestrial biosphere(including fresh water systems), the oceans and the sediments(including fossil fuels). The exchange rate of carbon betweenpools is referred to as flux. These reservoirs are either carbonsources and sinks. Carbon sinks absorb carbon from anotherpart of the carbon cycle while carbon sources release carbon.For example, green plants absorb carbon from the atmosphereand are considered a carbon sink. An industrial plant whichreleases carbon in the atmosphere is considered a carbonsource.

40 Climate Change. Forests and Forest Management

Chapter 4 THE GLOBAL CARBON CYCLE

21. WHAT PROCESSES EXIST FOR THE EXCHANGE OF CARBON BETWEEN THE A TMOSPHERE. THE OCEANS AND THE LAND?

There is a finite but extremely large amount of carbon on the Earth (Table 4.1). Carbon occurs in the ocean, in soils, fossil carbon reserves, bedrock. the atmosphere and plant biomass. The carbon cycle is the movement of carbon, in its various forms, between the Earth's surface. its interior and atmosphere. The major pathways of the exchange of carbon are photo-synthesis, respiration and oxidation. Movement occurs between living organisms, the atmosphere, the land and water (Fig 4.1). Over the course of millions of years, the carbon cycle has concentrated large amounts of carbon in bedrock, primarily as limestone and in fossil fuels.

The carbon cycle is thought of as four interconnected reservoirs or pools; the atmosphere, the terrestrial biosphere (including fresh water systems), the oceans and the sediments (including fossil fuels). The exchange rate of carbon between pools is referred to as flux. These reservoirs are either carbon sources and sinks. Carbon sinks absorb carbon from another part of the carbon cycle while carbon sources release carbon. For example, green plants absorb carbon from the atmosphere and are considered a carbon sink. An industrial plant which releases carbon in the atmosphere is considered a carbon source.


22. HOW ARE EXCHANGES OF CARBON BETWEENRESERVOIRS EXPRESSED?

Exchange between reservoirs involves large amounts ofcarbon. This is expressed in multiples of metric tonnes. Theunits used throughout this paper are those widely used in theliterature on climate change and carbon flux and are defined asfollows:

1 .teragramme (Tg) = 1012 grams or 106 tonnes.1 petagramme (Pg) = 1015 grams or 109 tonnes.1 gigatonne (Gt) -= 109 tonnes or 1 Pg.1 Pg 1 Gt.

Concentration of GHGs in the atmosphere are expressed asfollows:

Parts per million by volume.Parts per billion (thousandmillion) by volume.Parts per trillion (million million)by volume.

TABLE 4.1

ESTIMATED DISTRIBUTION OF THE GLOBALCARBON POOL (Source: Sombroek et al 1993)

Component GtC

Oceans 38000Fossil carbon

reserves 6000Soils

Organic carbon 1200Calcium carbonate 720

Atmosphere 720Plant biomass 560-835

Total 47220-47495

ppmv =ppbv =

pptv =


22, HOW ARE EXCHANGES OF CARBON BETWEEN RESERVOIRS EXPRESSEO?

Exchange between reservoirs involves large amounts of carbon. This is expressed in multiples of metric tonnes. The units used throughout this paper are those widely used in the literature on climate change and carbon flux and are defined as follows:

1 teragramme (Tg) = 1 petagramme (Pg) = 1 gigatonne (Gt) = 1 Pg =

1012 grams or 106 tonnes. 1 a" grams or 1 a' tonnes. 1 a' tonnes or 1 Pg. 1 Gt.

Concentration of GHGs in the atmosphere are expressed as follows:

ppmv = ppbv =

pptv =

Parts per million by volume. Parts per billion (thousand million) by volume. Parts per trillion (million million) by volume.

TABLE 4.1

ESTIMATED DISTRIBUTION OF THE GLOBAL CARBON POOL (Source: Sombroek et al 19931

Component GtC

Oceans 38000 Fossil carbon

reserves 6000 Soils

Organic carbon 1200 Calcium carbonate 720

Atmosphere 720 Plant biomass 560·835

Total 47220-47495


DEFORESTATION

:Ow50

SQL AND DETRITUS

1500

1000 +1/YEAR_BIOTA 344-- 40

5 37V

INTERMEDIATE AND DEEPWATERS

31j 4 °"°

38000 - 2/YEAR

0.2

Figure 4.1 - Schematic representation of the global carbon cycleshowing movement of carbon (in Gt) betvveen carbon sources andsinks (Source: Watson et al 1990).

ATMOSPHERE 750 + 3/YEAR

102 50 92 90

LAND BIOTA

550SURFACE OCEAN

42

DEFORESTATION

2 5


ATMOSPHERE 750 + 3{yEAA

102

LAND BIOTA

550

50

50

SOIL AND DETRITUS

1500

92 90

SURFACE OCEAN

BIOTA 3 1000 +l{yEAR

36

37

30000 - 2/YEAR

0.2

Figure 4.1 - Schematic representation of the global carbon cycle showing movement of carbon (in Gt) between carbon sources and sinks (Source: Watson et al 1990).


23. WHAT IS THE PRESENT LEVEL OF CARBONEXCHANGE BETWEEN THE ATMOSPHERE, THEOCEANS AND THE LAND?

According to estimates for the decade 1980-89, annual carbonfluxes due to CO2 exchanges were as follows (IPCC 1994):

CO2 sources:

Fossil fuel emissions 5.5 ±0.5 GtC/yr

Net emissions from tropicalland use (deforestation etc)Total emissions

CO2 sinks:

Additional terrestrial sinks(eg CO2 fertilization effect,nitrogen fertilization andclimatic effects)

1.6 ± 1.07.0± 1.1

Accumulation in theatmosphere 3.2 ±0.2

Uptake by the ocean 2.0 ±0.8

Uptake by northern hemisphereforest regrowth 0.5 ±0.5

1.4±1.5

The "additional terrestrial sinks" have not yet been quantifiedbut are believed to be the primary components of the so called"missing carbon sink" which is yet to be accounted for.


23, WHA T IS THE PRESENT LEVEL OF CARBON EXCHANGE BETWEEN THE A TMOSPHERE, THE OCEANS AND THE LAND?

According to estimates for the decade 1980-89, annual carbon fluxes due to CO, exchanges were as follows (lPCC 1994):

CO, sources:

Fossil fuel emissions

Net emissions from tropical land use (deforestation etc) Total emissions

CO, sinks:

Accumulation in the

5.5 ±0.5 GtC/yr

1.6±1.0 7.0±1.1

atmosphere 3.2±0.2

Uptake by the ocean 2.0 ± 0.8

Uptake by northern hemisphere forest regrowth 0.5 ±0.5

Additional terrestrial sinks (eg CO, fertilization effect, nitrogen fertilization and climatic effects) 1 .4 ± 1 .5

The "additional terrestrial sinks" have not yet been quantified but are believed to be the primary components of the so called "missing carbon sink" which is yet to be accounted for.


* Includes Russia

main stems of trees. Because of the long life span of mosttrees and their relatively large sizes, trees and forests arestorehouses of carbon. Overall, forests store from 20 to 100times more carbon per unit area than croplands and play acritical role in regulating the level of atmospheric carbon.The world's forests have been estimated to contain up to 80%of all above ground terrestrial carbon and approximately 40%of all below ground terrestrial carbon (soil, litter and roots).This amounts to roughly 1146 GtC. Approximately 37% ofthis carbon is stored in low latitude (tropical) forests, 14% inmid latitude (temperate) forests and 49% in high latitudeforests (Dixon et al 1994).

When trees die or are harvested, the stored carbon is released.Some of the carbon becomes part of the organic mattercomponent of forest soils where, depending on climaticconditions, it can remain for long periods. The remainder isreleased into the atmosphere, largely as CO2 but also as CH,or other GHGs. The rate of release may be slow, as in thecase of a single tree dying and being subject to years ofbreakdown and decay by fungi, insects, bacteria and other

TABLE 5.1

LAND AREA COVERED BY FORESTS AND OTHER WOODEDAREAS BY REGION (1980) (Source: Lanly 1989, FAO, unpublished data)

Region Forests (%) Other wooded(%)

Total(%)

Africa 18.0 21.3 39.3Americas 37.0 15.2 55.2Asia-Pacific 19.0 7.0 26.0Europe 27.0 8.6 35.6

WORLD 27.0 13.0 40.0


TABLE 5.1

LAND AREA COVERED BY FORESTS AND OTHER WOODED AREAS BY REGION (1980) (Source : Lanly 1989, FAO, unpublished data)

Region Forests (%) Other wooded Total 1%) 1%)

Africa 18.0 21.3 39.3 Americas 37 .0 15.2 55.2 Asia-Pacific 19.0 7.0 26.0 Europe· 27.0 8.6 35.6

WORLD 27.0 13.0 40 .. 0

• Includes Russia

main stems of trees. Because of the long life span of most trees and their relatively large sizes, trees and forests are storehouses of carbon. Overall, forests store from 20 to 100 times more carbon per unit area than croplands and play a critical role in regulating the level of atmospheric carbon. The world's forests have been estimated to contain up to 80% of all above ground terrestrial carbon and approximately 40% of all below ground terrestrial carbon (soil, litter and roots). This amounts to roughly 1146 GtC. Approximately 37% of this carbon is stored in low latitude (tropical) forests, 14% in mid latitude (temperate) forests and 49% in high latitude forests (Dixon et al 1994).

When trees die or are harvested, the stored carbon is released. Some of the carbon becomes part of the organic matter component of forest soils where, depending on climatic conditions, it can remain for long periods. The remainder is released into the atmosphere, largely as CO, but also as CH. or other GHGs. The rate of release may be slow, as in the case of a single tree dying and being subject to years of breakdown and decay by fungi, insects, bacteria and other


organisms. On the other hand, a sudden disturbance, such asa wildfire or clearing and burning of forests for agriculture andsettlement by humans, can cause a rapid release of largevolumes of GHGs into the atmosphere.

HOW MUCH CARBON IS RELEASED AND HOW MUCHIS TAKEN UP ANNUALL Y BY FORES Ts?

Estimates for the year 1 990 indicate that the low latitudeforests emitted 1.6 ± 0.4 GtC per year into the atmosphere,primarily due to deforestation. This is equivalent toapprOximately 23% of the total carbon emissions including theburning of fossil fuels. This was offset by a sequestration of0.7 ± 0.2 GtC per year by forest expansion and growth in themid and high latitudes (Table 5.2). Consequently, there ispresently a net carbon contribution of 0.9 ± 0.4 GtC per yearto the atmosphere from the world's forest ecosystems (Dixonet al 1994). This is undoubtedly due to increased rates oftropical deforestation during the decade of the 1980s (seequestion 25). At the beginning of the decade, the estimatedaccumulation of carbon in recovering tropical landscapeswhich had previously been disturbed was roughly equal to netcarbon emissions due to tropical deforestation and associatedburning (Lugo and Brown 1992).

DO DIFFERENT FOREST ECOSYSTEMS VARY IN THEIRCAPACITY TO ABSORB AND STORE CARBON?

Forests vary considerably in their capacity to absorb and storecarbon. Factors which influence carbon absorption ratesinclude temperature, precipitation, stocking, soil, slope,elevation, site conditions, growth rates and age. Generallyspeaking, closed forests have a greater capacity to storecarbon than open forests and woodlands. Undisturbed forestsstore more carbon than degraded forests. Wet or moist


organisms. On the other hand, a sudden disturbance, such as a wildfire or clearing and burning of forests for agriculture and settlement by humans, can cause a rapid release of large volumes of GHGs into the atmosphere.

26. HOW MUCH CARBON IS RELEASED AND HOW MUCH IS TAKEN UP ANNUALL Y BY FORESTS?

Estimates for the year 1990 indicate that the low latitude forests emitted 1.6 ± 0.4 GtC per year into the atmosphere, primarily due to deforestation. This is equivalent to approximately 23% of the total carbon emissions including the burning of fossil fuels. This was offset by a sequestration of 0.7 ± 0.2 GtC per year by forest expansion and growth in the mid and high latitudes (Table 5.2). Consequently, there is presently a net carbon contribution of 0.9 ± 0.4 GtC per year to the atmosphere from the world's forest ecosystems (Dixon et al 1994). This is undoubtedly due to increased rates of tropical deforestation during the decade of the 1980s (see question 25). At the beginning of the decade, the estimated accumulation of carbon in recovering tropical landscapes which had previously been disturbed was roughly equal to net carbon emissions due to tropical deforestation and associated burning (Lugo and Brown 1992).

27. DO DIFFERENT FOREST ECOSYSTEMS VARY IN THEIR CAPACITY TO ABSORB AND STORE CARBON?

Forests vary considerably in their capacity to absorb and store carbon. Factors which influence carbon absorption rates include temperature, precipitation, stocking, soil, slope, elevation, site conditions, growth rates and age. Generally speaking, closed forests have a greater capacity to store carbon than open forests and woodlands. Undisturbed forests store more carbon than degraded forests. Wet or moist


TABLE 5.2

ESTIMATED ANNUAL RATES OF CARBONEXCHANGE BETWEEN THE WORLD'S

FORESTS AND THE ATMOSPHERE

* Includes continental USA and Alaska.** Includes Nordic countries*** + Indicates transfer from atmosphere to forest.

- Indicates transfer from forest to atmosphere.

Source: Dixon et al 1994

Latitudinal Belt Carbon Exchange(GtfYear) ***

HighRussia +0.30 to +0.50Canada +0.08

Subtotal +0.48 ±0.1

MidUSA* +0.10 to +0.25Europe*" +0.09 to +0.12China -0.02Australia trace

Subtotal +0.26 ±0.09

LowAsia -0.50 to -0.90Africa -0.25 to -0.45Americas -0.50 to -0.70

Subtotal -1.65 ± 0.40

Total -0.9 ± 0.4


TABLE 5.2

ESTIMATED ANNUAL RATES OF CARBON EXCHANGE BETWEEN THE WORLD'S

FORESTS AND THE ATMOSPHERE

Latitudinal Belt

High Russia Canada

Subtotal

Mid USA' Europe- it

China Australia

Subtotal

Low Asia Africa Americas

Subtotal

Total

Carbon Exchange (Gt/Year) * ••

+0.30 to +0.50 +0.08

+0.48 ±O.'

+0.'0 to +0.25 + 0.09 to + 0 . '2 -0.02

trace

+0.26 ±0.09

-0.50 to -0.90 -0.25 to -0.45 -0.50 to -0.70

-, .65 ± 0 .40

·0.9 ± 0.4

, Includes continental USA and Alaska. •• Includes Nordic countries it. it + Indicates transfer from atmosphere to forest .

. Indicates transfer from forest to atmosphere.

Source: Dixon et al '994

C//mate Change, Forests and Forest Management 4.9

forests store more carbon than dry or semi-arid forests andmature forests store greater quantities of carbon than doyoung forests.

Many studies have been conducted to estimate the biomass offorest ecosystems. These can be used to estimate carbonstorage. The ratio of dry total biomass to carbon is roughly2:1. The carbon content of an undisturbed tropical moistforest can range has high as 250 tC/ha of standing, aboveground biomass. The carbon content of tropical, dry forestswith open, discontinuous canopies, on the other hand,generally averages less than 40 tC/ha (Brown and Lugo 1984)(Table 5.3).

Forest soils also store carbon. A recent study indicates that84.3% of the total carbon content of high latitude forests isstored in the soil. For mid-latitude forests, 63% is stored inthe soil and for low latitude forests, the proportion is 50.4%(Dixon et al 1994) (Table 5.4).

28. DO TREES AND FORESTS REMOVE CARBON FROMTHE EARTH'S ATMOSPHERE AT DIFFERENT RATESDURING DIFFERENT STAGES IN THEIR LIVES?

The rate of carbon absorption by trees and forests is afunction of growth rates and age. Generally speaking, treesand forests remove atmospheric carbon at high rates whenthey are young and fast growing. As stands approachmaturity and growth rates are reduced, the net carbonabsorption is also reduced. In theory, mature forests reach astage of equilibrium with respect to carbon absorption.Roughly an equal amount of carbon is released through decayof dead and diseased trees as is absorbed. However this israrely achieved in natural forests. Mature forests, if leftundisturbed, as is the case in reserved or protected forests,are carbon reservoirs but not necessarily net carbon sinks.


forests store more carbon than dry or semi-arid forests and mature forests store greater quantities of carbon than do young forests.

Many studies have been conducted to estimate the biomass of forest ecosystems. These can be used to estimate carbon storage. The ratio of dry total biomass to carbon is roughly 2: 1. The carbon content of an undisturbed tropical moist forest can range has high as 250 tC/ha of standing, above ground biomass. The carbon content of tropical, dry forests with open, discontinuous canopies, on the other hand, generally averages less than 40 tC/ha (Brown and Lugo 1984) (Table 5.3).

Forest soils also store carbon . A recent study indicates that 84.3% of the total carbon content of high latitude forests is stored in the soil. For mid-latitude forests, 63% is stored in the soil and for low latitude forests , the proportion is 50.4% (Dixon et al 1994) (Table 5.41 .

28. DO TREES AND FORESTS REMOVE CARBON FROM THE EARTH'S A TMOSPHERE A T DIFFERENT RA TES DURING DIFFERENT STAGES IN THEIR LIVES?

The rate of carbon absorption by trees and forests is a function of growth rates and age . Generally speaking, trees and forests remove atmospheric carbon at high rates when they are young and fast growing . As stands approach maturity and growth rates are reduced, the net carbon absorption is also reduced. In theory, mature forests reach a stage of equilibrium with respect to carbon absorption. Roughly an equal amount of carbon is released through decay of dead and diseased trees as is absorbed. However this is rare ly achieved in natural forests. Mature forests, if left undisturbed, as is the case in reserved or protected forests, are carbon reservoirs but not necessarily net carbon sinks.


TABLE 5.3

ESTIMATES OF AVERAGE ABOVE GROUND STOREDCARBON/HA BY VARIOUS VEGETATION COMMUNITIES

(Based on biomass values from Olsen et al(1983))

Holdridge Life Zone tC/ha

Forest

Tropical wet 100Tropical moist 70Tropical dry 50Subtropical wet 65Subtropical moist 35

Warm temperate 50Warm dry temperate 25Cool temperate 50

Wet boreal 55Moist boreal 40

Non Forest

Tropical thorn woodland 15Temperate thorn steppe 8

Cool temperate steppe 5Tropical desert bush 2Temperate desert bush 3

Boreal desert 5

Tundra 2.5


TABLE 5.3

ESTIMATES OF AVERAGE ABOVE GROUND STORED CARBON/HA BY VARIOUS VEGETATION COMMUNITIES

(Based on biomass values from Olsen et al(1 983))

Holdridge Life Zone tC/ha

Forest

Tropical wet lOO Tropical moist 70 Tropical dry 50 Subtropical wet 65 Subtropical moist 35

Warm temperate 50 Warm dry temperate 25 Cool temperate 50

Wet boreal 55 Moist boreal 40

Non Forest

Tropical thorn woodland 15 Temperate thorn steppe 8 Cool temperate steppe 5 Tropical desert bush 2 Temperate desert bush 3 Boreal desert 5 Tundra 2.5


Includes Nordic countries.

Source: Dixon et al 1994.

TABLE 5.4

ESTIMATED CARBON DENSITIES PER UNIT OF FOREST AREAIN VEGETATION AND SOILS OF THE WORLD'S FORESTS

Latitudinal Belt Carbon Densities (tC/ha)

Vegetation Soils

HighRussia 83 281Canada 28 484Alaska 39 212

Mean 64 (15.7%) 343 (84.3%)

MidUSA 62 108Europe* 32 90China 114 136Australia 45 83

Mean 57 (37%) 96 (63%)

LowAsia 132-174 139Africa 99 120Americas 130 120

Mean 121 (49.6%) 123 (50.4%)


TABLE 5.4

ESTIMATED CARBON DENSITIES PER UNIT OF FOREST AREA IN VEGETATION AND SOILS OF THE WORLD'S FORESTS

Latitudinal Belt Carbon Densities ItC/ha)

Vegetation Soils

High Russia 83 281 Canada 28 484 Alaska 39 212

Mean 64 115.7%) 343 184.3%)

Mid USA 62 108 Europe· 32 90 China 114 136 Australia 45 83

Mean 57 137%) 96 163%)

Low Asia 132-174 139 Africa 99 120 Americas 130 120

Mean 121 149.6%) 123150.4%)

• Includes Nordic countries.

Source: Dixon et al 1994.

51

52 Clifnate Change, Forests and Forest Management

Box 5.1 The role of forest plantations inNew Zealand's carbon balance.

According to estimates made by a team ofresearch scientists in New Zealand, thecountry's 1.24 million ha of plantationforests absorbed 4.5 ± 0.8 million tonnesof carbon between 1 April 1988 and 1 April1989. The total above ground carbonstored in New Zealand's forest plantationestate is approximately 88 million tonnes.

Carbon absorption by New Zealand's forestplantations for the period studied wasequivalent to approximately 70% of thecountry's fossil fuel emissions but <0.1%of the total global fossil fuel emissions.

The high annual rate of carbon uptake bythese plantations is a consequence of thelarge area of new plantings establishedduring the 1970s and 1980s. Withoutcontinued new plantings, the net annualrate of carbon absorption of theseplantations will rapidly approach zero(Hollinger et al 1993) .


Box 5.1 The role of forest . plantations in New Zealand's carbon balance.

According to estimates made by a team of research scientists in New Zealand, the country's 1.24 million ha of plantation forests absorbed 4.5 ± 0.8 million tonnes of carbon between 1 April 1988 and 1 April 1989. The total above ground carbon stored in New Zealand's forest plantation estate is approximately 88 million tonnes.

Carbon absorption by New Zealand's forest plantations for the period studied was equivalent to approximately 70% of the country's fossil fuel emissions but < 0.1 % of the total global fossil fuel emissions.

The high annual rate of carbon uptake by these plantations is a consequence of the large area of new plantings established during the 1970s and 1980s. Without continued new plantings, the net annual rate of carbon absorption of these plantations will rapidly approach zero (Hollinger et al 1993) .


Studies of carbon absorption rates in tropical forest plantationsindicate that maximum growth and carbon uptake occursduring age classes 0-5 and 6-10 years (62%). Carbon uptakedecreases by about 50% during the next 5 years anddecreases even further after age 16 (Brown et al 1986).29.

29. WHICH HUMAN ACTIVITIES IN FORESTS ANDWOODLANDS CONTRIBUTE TO INCREASES IN THELEVELS OF GHGS?

DEFORESTA TION - Felling and burning of forests to make landavailable for agriculture or livestock grazing, is the major forestsector contributor to increases in the levels of GHGs and is thesecond largest human caused source of GHGs.

Human societies have been cutting forests for millennia. Untilthe early part of this century, deforestation occurred mainly intemperate forests. More recently, it has been concentrated inthe tropics. Deforestation, and associated burning, results ina massive and rapid release of carbon into the atmosphere,primarily as CO2. Smaller amounts of CH4 and CO are alsoemitted. Tropical forests play an important role in the globalcarbon cycle because they store about 50% of the world'sliving terrestrial carbon (Dixon et al 1994). High rates ofdeforestation in the tropics is the reason that forests presentlymake a net contribution to atmospheric carbon, despite thefact that they are able to store large quantities of carbon.

Deforestation can also alter climate directly by increasingreflectivity (albedo) and decreasing evapo-transpiration.Experiments with climate models predict that the replacementof all of the forests of the Amazon Basin with grassland wouldreduce the rainfall over the basin by about 20% and increasethe average regional temperature by several degrees (Maunder1990).


Studies of carbon absorption rates in tropical forest plantations indicate that maximum growth and carbon uptake occurs during age classes 0-5 and 6-10 years (62%). Carbon uptake decreases by about 50% during the next 5 years and decreases even further after age 16 (Brown et al 1986).29.

29. WHICH HUMAN ACTIVITIES IN FORESTS AND WOODLANDS CONTRIBUTE TO INCREASES IN THE LEVELS OF GHGS?

DEFORESTA TION - Felling and burning of forests to make land available for agriculture or livestock grazing, is the major forest sector contributor to increases in the levels of GHGs and is the second largest human caused source of GHGs.

Human societies have been cutting forests for millennia. Until the early part of this century, deforestation occurred mainly in temperate forests. More recently, it has been concentrated in the tropics. Deforestation, and associated burning, results in a massive and rapid release of carbon into the atmosphere, primarily as CO 2 , Smaller amounts of CH, and CO are also emitted. Tropical forests play an important role in the global carbon cycle because they store about 50% of the world's living terrestrial carbon (Dixon et al 1994). High rates of deforestation in the tropics is the reason that forests presently make a net contribution to atmospheric carbon, despite the fact that they are able to store large quantities of carbon.

Deforestation can also alter climate directly by increasing reflectivity (albedo) and decreasing evapo-transpiration. Experiments with climate models predict that the replacement of all of the forests of the Amazon Basin with grassland would reduce the rainfall over the basin by about 20% and increase the average regional temperature by several degrees (Maunder 1990).


BIOMASS BURNING - The term "biomass burning" includesall intentional human activities associated with forest clearing,the burning of savanna vegetation to stimulate regeneration ofgrasses for livestock, burning of fuel wood and charcoal andconsumption of agricultural residues. The area of savannavegetation burned each year is estimated at 750 million ha.About half of this area is in Africa (Fig 5.1). Shiftingcultivation, a practice in which the natural vegetation iscleared, used for agriculture for 2 to 5 years and then allowedto remain fallow and revegetate with natural vegetation for 7to 12 years before being cleared again, is practised by 200million people world wide on 300 to 500 million ha.Approximately 87% of the biomass burning occurs in thetropics.

WILDFIRES - A "wildfire" is defined as any fire occurring onwild (undeveloped) lands except a fire under prescription (onewhich is set intentionally) (FAO 1986). Recent estimatesindicate that between 12 and 13 million ha of forests andother wooded lands are burned annually (Calabri and Ciesla1992). With the exception of remote forest areas in portionsof North America and Siberia, most forest and other wildlandfires are of human origin. Human causes of wildfires includeescaped prescribed fires, carelessness, and arson. Naturalcauses of wildfires are lightning storms, volcanic activity andburning of underground peat and coal deposits.

OTHER ACTIVITIES - Other human activities connected withforests and forest products which contribute to elevated levelsof greenhouse gases include degradation of forests anddisposal of wood products, especially paper products, afterthey have served their period of usefulness.


B/OMASS BURNING - The term "biomass burning" includes all intentional human activities associated with forest clearing, the burning of savanna vegetation to stimulate regeneration of grasses for livestock, burning of fuel wood and charcoal and consumption of agricultural residues. The area of savanna vegetation burned each year is estimated at 750 million ha. About half of this area is in Africa (Fig 5.1) . Shifting cultivation, a practice in which the natural vegetation is cleared, used for agriculture for 2 to 5 years and then allowed to remain fallow and revegetate with natural vegetation for 7 to 12 years before being cleared again, is practised by 200 million people world wide on 300 to 500 million ha . Approximately 87% of the biomass burning occurs in the tropics.

W/LDFIRES - A "wildfire" is defined as any fire occurring on wild (undeveloped) lands except a fire under prescription (one which is set intentionally) (FAO 1986). Recent estimates indicate that between 12 and 13 million ha of forests and other wooded lands are burned annually (Calabri and Ciesla 1992). With the exception of remote forest areas in portions of North America and Siberia, most forest and other wildland fires are of human origin. Human causes of wildfires include escaped prescribed fires, carelessness, and arson. Natural causes of wild fires are lightning storms, volcanic activity and burning of underground peat and coal deposits.

OTHER ACTIVITIES - Other human activities connected with forests and forest products which contribute to elevated levels of greenhouse gases include degradation of forests and disposal of wood products, especially paper products, after they have served their period of usefulness.

Figure 5.1 - An aerial view of a brush fire in the Sudan. Roughly750 million ha of savanna vegetation are burned annually, resultingin a massive release of greenhouse gases.

30. WHAT ARE THE CURRENT RATES OFDEFORESTATION IN THE WORLD'S FORESTS?

The average annual rate of tropical deforestation during thedecade of 1981-90 was 15.4 million ha (FAO 1993). Theserates of deforestation are roughly equivalent to the total landarea of Nepal, Nicaragua or Greece and resulted in a reductionin the area of tropical forests from 1 910 million ha at the endof 1980 to 1 756 million ha at the end of 1990. On a regionalbasis, the annual loss of forest cover was: Latin America andthe Caribbean, 7.4 million ha (0.8% of the total forest area),Asia and the Pacific, 3.9 million ha (1.2 %) and Africa, 4.1million ha (0.7%). The forest area of the temperate and borealzones did not change significantly during the same period.

Climate Change, Forests and Forest Management 55Climate Change, Forests and Forest Management 55

Figure 5.1 - An aerial view of a brush fire in the Sudan . Roughly 750 million ha of savanna vegetation are burned annually, resulting in a massive release of greenhouse gases.

30. WHA T ARE THE CURRENT RA TES OF DEFORESTA TlON IN THE WORLD'S FORESTS?

The average annual rate of tropical deforestation during the decade of 1981-90 was 15.4 million ha (FAO 1993). These rates of deforestation are roughly equivalent to the total land area of Nepal, Nicaragua or Greece and resulted in a reduction in the area of tropical forests from 1 910 million ha at the end of 1980 to 1 756 million ha at the end of 1990. On a regional basis, the annual loss of forest cover was: Latin America and the Caribbean, 7.4 million ha (0.8 % of the total forest area), Asia and the Pacific, 3.9 million ha (1.2 %) and Africa, 4 .1 million ha (0 .7 % ). The forest area of the temperate and boreal zones did not change significantly during the same period .


Annual rates of deforestation in the tropics have increasedwhen compared to the previous decade. During the 1980s,the annual rate of tropical deforestation was 11.3 million ha(Lanly 1982).

Forests in developed temperate regions now cover muchsmaller areas than in the past. These forests have historicallycontributed heavily to global carbon emissions as forests inEurope and North America were cleared for agriculture.However, the area of these forests has stabilized and evenincreased slightly over the past 100 years as agricultural landswere abandoned and reverted to forest cover. France, forexample, had forest cover on only 14% of the country's landarea in 1798. Today 27% of its land area is forested.Deforestation and agricultural development in the state ofVermont, USA had reduced the surface area of forest cover toabout 15% of the total land area about 100 years ago. Todaythe state is 85% forested.

31. HOW ARE FOREST SOILS AFFECTED BYDEFORESTATION?

In addition to increasing susceptibility of soils to erosion bywind and water, the clearing of forests and woodlands tosupport agriculture in the tropics can result in a loss of 20 to50% of the soil carbon contained in the topsoil. Someestimates indicate that deforestation in the tropics caused anet release of between 0.1 and 0.3 Gt of soil carbon in theyears around 1990 compared with 0.3 and 1.3 Gt as a resultof burning and decay of vegetation respectively (Sombroek etal 1993).


Annual rates of deforestation in the tropics have increased when compared to the previous decade. During the 1980s, the annual rate of tropical deforestation was 11.3 million ha (Lanly 1982).

Forests in developed temperate regions now cover much smaller areas than in the past. These forests have historically contributed heavily to global carbon emissions as forests in Europe and North America were cleared for agriculture. However, the area of these forests has stabilized and even increased slightly over the past 100 years as agricultural lands were abandoned and reverted to forest cover. France, for example, had forest cover on only 14% of the country's land area in 1798. Today 27% of its land area is forested. Deforestation and agricultural development in the state of Vermont, USA had reduced the surface area of forest cover to about 15% of the total land area about 100 years ago. Today the state is 85% forested.

31. HOW ARE FOREST SOILS AFFECTED BY DEFORESTA TlON?

In addition to increasing susceptibility of soils to erosion by wind and water, the clearing of forests and woodlands to support agriculture in the tropics can result in a loss of 20 to 50% of the soil carbon contained in the topsoil. Some estimates indicate that deforestation in the tropics caused a net release of between 0 .1 and 0.3 Gt of soil carbon in the years around 1990 compared with 0.3 and 1.3 Gt as a result of burning and decay of vegetation respectively (Sombroek et al 1993).


Chapter 6POSSIBLE EFFECTS OF CLIMATE

CHANGE ON FORESTS

32. WHAT CHANGES IN GRO WTH AND YIELD OF TREESAND FORESTS CAN BE EXPECTED AS A RESULT OFCLIMA TE CHANGE?

The implications of CO2 enrichment on growth and yield oftrees and forests are still unclear. Laboratory studies ongrowth rates and yield of plants grown in elevated CO2environments have documented increased rates ofphotosynthesis, lowered plant water use requirements,increased carbon sequestration and increased soil microbialactivity. These result in higher rates of nitrogen fixation,thereby stimulating growth. However in a natural ecosystem,where animals graze on plants, disease organism causedamage and tree death and plants compete for available light,water and nutrients, there are serious doubts that productionwould actually increase. In addition, higher growth and yieldcould be offset by higher losses due to fire, insects anddisease (See questions 35 and 36).

To date, little work has been done to test the effects of higherCO2 concentrations on forests or other natural plantcommunities over extended time frames. Therefore the neteffect of climate change on forest growth and yield uncertain.Sedjo and Solomon (1989) conclude that the phenomenon ofCO2 fertilization has not yet been detected in trees, despiteextensive searches for it in the field and in growth chambers.


Chapter 6 POSSIBLE EFFECTS OF CLIMATE

CHANGE ON FORESTS

32, WHA T CHANGES IN GROWTH AND YIELD OF TREES AND FORESTS CAN BE EXPECTED AS A RESUL T OF CL/MA TE CHANGE?

The implications of CO, enrichment on growth and yield of trees and forests are still unclear. Laboratory studies on growth rates and yield of plants grown in elevated CO, environments have documented increased rates of photosynthesis, lowered plant water use requirements, increased carbon sequestration and increased soil microbial activity. These result in higher rates of nitrogen fixation, thereby stimulating growth. However in a natural ecosystem, where animals graze on plants, disease organism cause damage and tree death and plants compete for available light, water and nutrients, there are serious doubts that production would actually increase. In addition, higher growth and yield could be offset by higher losses due to fire, insects and disease (See questions 35 and 36).

To date, little work has been done to test the effects of higher CO, concentrations on forests or other natural plant communities over extended time frames. Therefore the net effect of climate change on forest growth and yield uncertain. Sedjo and Solomon (1989) conclude that the phenomenon of CO, fertilization has not yet been detected in trees, despite extensive searches for it in the field and in growth chambers.


33. WHAT CHANGES CAN BE EXPECTED IN THENATURAL RANGES OF TREE SPECIES AND PLANTCOMMUNITIES DUE TO CLIMA TE CHANGE?

When temperature and rainfall patterns change, the ranges ofboth animal and plant species change. As the Earth warms,species tend to shift their distributions toward higher latitudesand altitudes. For each 1°C of warming, tree ranges in thenorthern hemisphere have the potential to expand 100 kmnorthward while southern boundaries retreat. This is aprocess which has been tracked since the last Ice Age (Davis1989).

There is ample evidence in the fossil record that plants haveundergone significant range shifts in response to changingclimates. Analysis of fossil pollen data also providesinformation on the composition of past vegetation (Brubaker1975, Solomon and Bartlein 1992) (Fig 6.1). During thePleistocene interglacial eras, temperatures in North Americawere from 2° to 3° C higher than they are now. Tree speciessuch as sweetgum, Liquidambar styraciflua, and Osageorange, Maclura pomifera, which today are considered typicalcomponents of forest vegetation in the southeastern UnitedStates, occurred near Toronto, Canada. During the lastinterglacial era, which ended more than 100 000 years ago,areas covered presently with boreal vegetation in northwesternEurope, were predominantly temperate. More recently inSweden, the range of the birch, Betula pubescens, respondedrapidly to warming during the first half of the twentiethcentury by expanding its range northward into the tundra(Peters 1990).

Shifts in the ranges of tree species could be important forseveral reasons. First, there are indications that climate couldchange faster than some tree species can respond throughmigration. Second, new sites may not be edaphically suitablefor the migration of species. Finally, future climate zones,


33, WHA T CHANGES CAN BE EXPECTED IN THE NA TURAL RANGES OF TREE SPECIES AND PLANT COMMUNITIES DUE TO CL/MA TE CHANGE?

When temperature and rainfall patterns change, the ranges of both animal and plant species change. As the Earth warms, species tend to shift their distributions toward higher latitudes and altitudes. For each 1°C of warming, tree ranges in the northern hemisphere have the potential to expand 100 km northward while southern boundaries retreat. This is a process which has been tracked since the last Ice Age (Davis 1989).

There is ample evidence in the fossil record that plants have undergone significant range shifts in response to changing climates. Analysis of fossil pollen data also provides information on the composition of past vegetation (Brubaker 1975, Solomon and Bartlein 1992) (Fig 6.1). During the Pleistocene interglacial eras, temperatures in North America were from 2° to 3° C higher than they are now. Tree species such as sweetgum, Liquidambar styraciflua, and Osage orange, Maclura pomifera, which today are considered typical components of forest vegetation in the southeastern United States, occurred near Toronto, Canada. During the last interglacial era, which ended more than 100 000 years ago, areas covered presently with boreal vegetation in northwestern Europe, were predominantly temperate. More recently in Sweden, the range of the birch, Betula pubescens, responded rapidly to warming during the first half of the twentieth century by expanding its range northward into the tundra (Peters 1990).

Shifts in the ranges of tree species could be important for several reasons. First , there are indications that climate could change faster than some tree species can respond through migration. Second , new sites may not be edaphically suitable for the migration of species. Finally, future climate zones,


AGE(yeo,$)

3000

8000

3000

8000

CC

L.1Z

-

CAMP 11 LAKE (SILT LOAM)

LOST LAKE (SANO LOAM)

YELLOW DOG POND (SAND)

I t J t0 20 40 60 80 100 `10

PERCENTAGE OF TOTAL POLLEN

Figure 6.1 - Fossil pollen diagrams made from analysis of lakesediments in the Upper Peninsula of Michigan, USA. These dataprovide clues as to the composition of forests which occupied thisarea in the past (Source: Solomon and Bartlein 1992).

leading to displaced forest ecosystems will not be related tocurrent political boundaries and (or) land use patterns (Izrael etal 1990).

Studies have been done which predict shifts in the naturalranges of plant ecosystems (Fig 6.2) and individual treespecies which could result from temperature and moisturechanges due to atmospheric levels of GHGs. Miller et al

l.1_1

YCL L"s LL <1

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0000


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8000

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LOS T LAK E (SAND LOAM)

30oo l---

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YELLOW DOG POND (SAND)

3000

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l..l...l....LJ.-LI....L~ o 20 '10 60 80 tOO "~

~ z r • w 0 ~ u w ~ ~

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PERCENTAGE OF TOTAL POLLEN

59

w ~ w ~ > • ~ , ~ • • w

~ ~ > m • Z W , ~ 0 ~ > r

• ~ w 0 ~ ,-U ~ ~ r w 0

Figure 6.1 - Fossil pollen diagrams made from analysis of lake sediments in the Upper Peninsula of Michigan, USA. These data provide clues as to the composition of forests which occupied this area in the past (Source: Solomon and Bartlein 1992).

leading to displaced forest ecosystems will not be related to current political boundaries and (or) land use patterns (lzrael et al 1990).

Studies have been done which predict shifts in the natural ranges of plant ecosystems (Fig 6.2) and individual tree species which could result from temperature and moisture changes due to atmospheric levels of GHGs. Miller et aJ

Figure 6.3 - Possible redistribution of loblolly pine, Pinus taeda in thesoutheastern United States due to a doubling of atmospheric CO2(Source - Miller et al 1987).

LegendLoblay pine range

1 (Gain)

-2 (No change)

3 (Loss)

Figure 6.4 - Examples of species redistribution in high mountainregions due to a 2°C increase in mean annual temperature: a =mountains of eastern Africa resulting in a relatively small increase inarea and b = highlands of Uganda resulting in a near disappearanceof a high elevation vegetation zone (Source: Sombroek 1990).

62 Climate Change, Forests and Forest Management62 Climate Change, Forests and Forest Management

Legend

Labially pine range

~-lIGoin)

[eH -2 (No change)

~ -3 ILoss)

Figure 6.3 - Possible redistribution of loblolly pine, Pinus taeda in the southeastern United States due to a doubling of atmospheric CO2

(Source - Miller et al 1987).

0..)

lGOO~~ ~~-)A-~II~~---____ _ _ /

I I

I

\ , \ \

Figure 6.4 - Examples of species redistribution in high mountain regions due to a 2°C increase in mean annual temperature : a =

mountains of eastern Africa resulting in a relatively small increase in area and b = highlands of Uganda resulting in a near disappearance of a high elevation vegetation zone (Source: Sombroek 1990) .


Box 6.1 Will the future forests of the worldbe drier?

Plants may have reduced rates oftranspiration in an atmosphere with elevatedlevels of CO2. The outcome could be aworld with reduced cloud formation and lessrain, according to a report by the TerrestrialInitiative on Global Environmental Research(TIGER) of the Natural EnvironmentalResearch Council of the United Kingdom.

Several research groups have successfullylinked computer models of land surfaceprocesses to climate prediction models. Asimple climate model predicted nearly 10%more evaporation and 3% more rainfall overthe tropical rain forests in a future high CO2environment. However, when the rainforestwas described more realistically, a newchain of events was started, leading to lesswater being available for cloud formationand less evaporation and rain (WMO 1994).


Box 6.1 Will the future forests of the world be drier?

Plants may have reduced rates of transpiration in an atmosphere with elevated levels of CO,. The outcome could be a world with reduced cloud formation and less rain, according to a report by the Terrestrial Initiative on Global Environmental Research (TIGER) of the Natural Environmental Research Council of the United Kingdom.

Several research groups have successfully linked computer models of land surface processes to climate prediction models. A simple climate model predicted nearly 10% m9re evaporation and 3% more rainfall over the tropical rain forests in a future high CO, environment. However. when the rainforest was described more realistically, a new chain of events was started. leading to less water being available for cloud formation and less evaporation and rain (WMO 1994).

63


Sea level rise, associated with rising temperatures, couldeffect the distribution and abundance of mangrove forests.These coastal forests provide a wealth of wood and non woodforest products and services. In addition to meeting needs forwood products for the inhabitants of coastal zones in thetropics, they provide a rich habitat for fisheries andaquaculture. They also protect coastal zones from tropicalstorms and shoreline erosion and offer breeding sites for alarge number of wildlife species (FAO 1994, Gable et al 1990).

Future shifts in the natural ranges of trees and forestcommunities could have both positive and negative effects onsupplies of lumber and other forest products, distance tomarkets, species diversity and susceptibility to fire, pests anddisease.

34. WHAT IS THE LIKELIHOOD THAT CLIMA TE CHANGECOULD THREA TEN SOME SPECIES OR PLANTCOMMUNITIES WITH EXTINCTION?

The likelihood that plant or animal species could be lost due toclimate change is uncertain. Because of their mobility, animalsare generally at less risk because they are able to disperse tohabitats which are more favourable. Plants, on the otherhand, are stationary, and must rely on dispersal of seeds fromareas which are no longer favourable to new areas resulting ina gradual shift in the their natural ranges. During thePleistocene glacial eras many tree species were lost from theboreal and temperate forests of Europe because they wereunable to shift their ranges southward due to the presence ofthe Alps, the Pyrenees and other predominantly east-westmountain ranges which served as a natural barrier to plantmigration. Consequently, the forests of northern Europecontain considerably fewer species than those which occur atequivalent latitudes in Asia and North America.


Sea level rise, associated with rising temperatures, could effect the distribution and abundance of mangrove forests. These coastal forests provide a wealth of wood and non wood forest products and services. In addition to meeting needs for wood products for the inhabitants of coastal zones in the tropics, they provide a rich habitat for fisheries and aquaculture. They also protect coastal zones from tropical storms and shoreline erosion and offer breeding sites for a large number of wildlife species (FAO 1994, Gable et al 1990).

Future shifts in the natural ranges of trees and forest communities could have both positive and negative effects on supplies of lumber and other forest products, distance to markets, species diversity and susceptibility to fire, pests and disease.

34. WHA T IS THE LIKELIHOOD THA T CLlMA TE CHANGE COULD THREA TEN SOME SPECIES OR PLANT COMMUNITIES WITH EXTINCTION?

The likelihood that plant or animal species could be lost due to climate change is uncertain. Because of their mobility, animals are generally at less risk because they are able to disperse to habitats which are more favourable. Plants, on the other hand, are stationary, and must rely on dispersal of seeds from areas which are no longer favourable to new areas resulting in a gradual shift in the their natural ranges. During the Pleistocene glacial eras many tree species were lost from the boreal and temperate forests of Europe because they were unable to shift their ranges southward due to the presence of the Alps, the Pyrenees and other predominantly east-west mountain ranges which served as a natural barrier to plant migration. Consequently, the forests of northern Europe contain considerably fewer species than those which occur at equivalent latitudes in Asia and North America.

Clima te Change, Forests and Forest Management 65

In general, plant ecologists believe that plant species withbroad geographic ranges and many populations will be themost likely to survive climate change. Examples includespecies such as Pinus sylvestris, which occurs from westernEurope to Siberia, Populus tremula and P. tremuloides, both ofwhich have transcontinental distributions. Rare orgeographically restricted species would be at greater risk ofextinction. This is especially true of species restricted to highelevation zones which would ultimately be unable to shift theirranges further upslope in response to a warmer climate. Anexample is the Fraser or southern balsam fir, Ab/es fraseri, atree whose natural range is restricted to the highest elevationsof six areas in the Southern Appalachian Mountains in theUnited States (Fig 6.5). Another category of plants which areat some risk of extinction are those with heavy seeds whichare not readily dispersed.

Figure 6.5 - A forest of Ab/es fraseri and Picea rubens straddles thehighest ridges in the Black Mountains of North Carolina, USA.Forests such as these would be unable to shift their ranges upslopein response to a warming climate.


In general, plant ecologists believe that plant species with broad geographic ranges and many populations will be the most likely to survive climate change. Examples include species such as Pinus sy/vestris, which occurs from western Europe to Siberia, Popu/us tremu/a and P. tremu/oides, both of which have transcontinental distributions. Rare or geographically restricted species would be at greater risk of extinction. This is especially true of species restricted to high elevation zones which would ultimately be unable to shift their ranges further upslope in response to a warmer climate. An example is the Fraser or southern balsam fir, Abies fraseri, a tree whose natural range is restricted to the highest elevations of six areas in the Southern Appalachian Mountains in the United States (Fig 6.5). Another category of plants which are at some risk of extinction are those with heavy seeds which are not readily dispersed.

Figure 6.5 . A forest of. Abies fraseri and Picea rubens straddles the highest ridges in the Black Mountains of North Carolina, USA. Forests such as these would be unable to shift their ranges ups lope in response to a warming climate.


Other ecologists argue that the risk of extinction of plantspecies and resultant loss of biodiversity is minimal becauseplants possess genetic variation which allows them to adaptto changing environmental conditions. Genetic variation is aprerequisite for evolution and a powerful mechanism whichallows both animals and plants to change and adapt (Erikssonet al 1993).

35. HOW MIGHT CLIMATE CHA NGE INFLUENCE THEINCIDENCE AND INTENSITY OF WILDFIRES?

As the structure, composition and biomass of forests respondto changing climate, so will the behaviour of fire (Fosberg etal 1990). Some expected changes include increases in thefrequency and severity of fires and a lengthening of fireseasons in areas which are already prone to fire events.

Some tropical rain forests are subject to periodic episodes ofprolonged droughts such as those caused by the El NiñoSouthern Oscillation (ENSO). These droughts can drasticallychange the fuel conditions and flammability of the vegetation.Once precipitation falls below 100 mm per month, and periodsof two or more weeks without rain occur, the forestvegetation sheds its leaves progressively with increasingdrought stress. In addition, the moisture content of surfacefuels is lowered, while fallen woody material and looselypacked leaf litter contributes to the build-up and spread ofsurface fires. Aerial fuels such as desiccated climbers andlianas become fire ladders leading to crown fires (Goldammerand Seibert 1990). It is this sequence of events which set thestage for the catastrophic fires which occurred in EastKalimantan, Indonesia during 1982-83 and resulted in thedestruction of over 3.5 million ha of primary and secondarymoist forest. Some global circulation models (GCM) predictincreased drought episodes in some tropical forests.Consequently the incidence of large wildfires, such as the oneswhich occurred in East Kalimantan, could increase.


Other ecologists argue that the risk of extinction of plant species and resultant loss of biodiversity is minimal because plants possess genetic variation which allows them to adapt to changing environmental conditions. Genetic variation is a prerequisite for evolution and a powerful mechanism which allows both animals and plants to change and adapt (Eriksson et al 1993).

35. HOW MIGHT CL/MA TE CHANGE INFLUENCE THE INCIDENCE AND INTENSITY OF WILDFIRES?

As the structure, composition and biomass of forests respond to changing climate, so will the behaviour of fire (Fosberg et al 1990). Some expected changes include increases in the frequency and severity of fires and a lengthening of fire seasons in areas which are already prone to fire events.

Some tropical rain forests are subject to periodic episodes of prolonged droughts such as those caused by the El Nifio Southern Oscillation (EN SO) . These droughts can drastically change the fuel conditions and flammability of the vegetation. Once precipitation falls below 100 mm per month, and periods of two or more weeks without rain occur, the forest vegetation sheds its leaves progressively with increasing drought stress. In addition, the moisture content of surface fuels is lowered, while fallen woody material and loosely packed leaf litter contributes to the build-up and spread of surface fires. Aerial fuels such as desiccated climbers and lianas become fire ladders leading to crown fires (Goldammer and Seibert 1990). It is this sequence of events which set the stage for the catastrophic fires which occurred in East Kalimantan, Indonesia during 1982-83 and resulted in the destruction of over 3.5 million ha of primary and secondary moist forest. Some global circulation models (GCM) predict increased drought episodes in some tropical forests . Consequently the incidence of large wild fires, such as the ones which occurred in East Kalimantan, could increase.


Certain tropical rain forests, especially those in the sub-equatorial tropics (from 10 to 23° latitude) are subject tohurricanes. Damage associated with these storms promotesinvasion of vines, which can contribute to foliar biomassaccumulation on soil surface openings, particularly duringoccasional dry spells. This results in fuel loadings that canlead to fires (Mueller-Dombois and Goldammer 1990).

Fuel accumulation resulting from the direct effects of tropicalstorms can also increase the hazard of wildfire. In 1988,Hurricane Gilbert swept across part of Mexico's YucatanPeninsula and damaged over 1 million ha of tropical forests.The volume of combustible fuel created by the debrisincreased the risk of wildfire. During the following year, over120,000 ha of Mexico's largest area of tropical forest burned(Ciesla 1993). One of the more uncertain effects of predictedclimate change is the possibility of an increased frequency andintensity of tropical storms. This would increase the levels ofcombustible fuels.

In some remote forest areas, lightning is a major cause of fire.A study using GCMs was done to determine lightningfrequency for a doubled CO, climatic regime. This studypredicts an increase in lightning frequency at all latitudes witha mean global increase of 26% (Fosberg et al 1990).

36. WHAT ARE THE EXPECTED EFFECTS OF CLIMA TECHANGE ON FOREST HEALTH INCLUDINGSUSCEPTIBILITY TO PESTS AND DISEASE ORDECLINE?

An increase in insect and disease caused losses in forestscould become one of the first observed effects of climatechange. Evidence of this can be found in the pest epidemicswhich are the result of stress brought on by periodic droughtor excess rainfall. Reviews by Kristiansen (1993) andSauerbeck (1992) of potential effects of climate change on


Certain tropical rain forests, especially those in the subequatorial tropics (from 10 to 23° latitude) are subject to hurricanes. Damage associated with these storms promotes invasion of vines, which can contribute to foliar biomass accumulation on soil surface openings, particularly during occasional dry spells. This results in fuel loadings that can lead to fires (Mueller-Dombois and Goldammer 1990).

Fuel accumulation resulting from the direct effects of tropical storms can also increase the hazard of wildfire. In 1988, Hurricane Gilbert swept across part of Mexico's Yucatan Peninsula and damaged over 1 million ha of tropical forests. The volume of combustible fuel created by the debris increased the risk of wildfire. During the following year, over 120,000 ha of Mexico's largest area of tropical forest burned (Ciesla 1993). One of the more uncertain effects of predicted climate change is the possibility of an increased frequency and intensity of tropical storms. This would increase the levels of combustible fuels.

In some remote forest areas, lightning is a major cause of fire. A study using GCMs was done to determine lightning frequency for a doubled CO 2 climatic regime. This study predicts an increase in lightning frequency at all latitudes with a mean global increase of 26% (Fosberg et al 1990).

36. WHA T ARE THE EXPECTED EFFECTS OF CLlMA TE CHANGE ON FOREST HEAL TH INCLUDING SUSCEPTIBILITY TO PESTS AND DISEASE OR DECLINE?

An increase in insect and disease caused losses in forests could become one of the first observed effects of climate change. Evidence of this can be found in the pest epidemics which are the result of stress brought on by periodic drought or excess rainfall. Reviews by Kristiansen (1993) and Sauerbeck (1 992) of potential effects of climate change on

68 Clima te Change, Forests and Forest Management

pests and diseases in agriculture provide a framework fromwhich to identify potential forest sector effects. They includeboth positive and negative responses.

Some anticipated negative effects on forest health are:

In a given location, higher temperatures couldresult in more generations of insect pests peryear, thus increasing their destructive potential.This is especially true for those insects whichalready have more than one generation a year.An example of a destructive forest insect oftropical forests whose number of generationscould increase under a warming scenario is thepine caterpillar, Dendrolimus punctatus, animportant defoliator of tropical pines in southernChina and Southeast Asia (Fig 6.6)

The ratios of pest species to their naturalenemies could change in favour of the pests.This would increase the reproductive potentialof destructive pests and result in higher levelsof damage.

Increased climatic anomalies are predicted tooccur as part of climate change. A higherincidence of droughts, storms, deep freezeevents or periods of excess rainfall will putadditional stresses on trees and forests makingthem more susceptible to attack by pests anddisease. Climatic anomalies may also increasethe sensitivity of trees to air pollution frornanthropogenic sources. Episodes of forestdecline may also increase. These are the resultof a complex interaction of forests with climate,site, pests and disease and, in many cases,human activities (Mueller-Dombois 1992).Examples include diebacks of Metrosideros


pests and diseases in agriculture provide a framework from which to identify potential forest sector effects. They include both positive and negative responses.

Some anticipated negative effects on forest health are:

•

•

•

In a given location, higher temperatures could result in more generations of insect pests per year, thus increasing their destructive potential. This is especially true for those insects which already have more than one generation a year. An example of a destructive forest insect of tropical forests whose number of generations could increase under a warming scenario is the pine caterpillar, Dendrolimus punctatus, an important defoliator of tropical pines in southern China and Southeast Asia (Fig 6.6)

The ratios of pest species to their natural enemies could change in favour of the pests. This would increase the reproductive potential of destructive pests and result in higher levels of damage.

Increased climatic anomalies are predicted to occur as part of climate change. A higher incidence of droughts, storms, deep freeze events or periods of excess rainfall will put additional stresses on trees and forests making them more susceptible to attack by pests and disease. Climatic anomalies may also increase the sensitivity of trees to air pollution from anthropogenic sources. Episodes of forest decline may also increase. These are the result of a complex interaction of forests with climate, site, pests and disease lInd, in many cases, human activities (Mueller-Dombois 1992). Examples include diebacks of Metrosideros

Figure 6.6 - Insects such as the pine caterpillar, Dendrolimuspunctatus, a destructive defoliator of tropical pines in SoutheastAsia, can undergo additional generations in warmer climates.

69C//mate Change, Forests and Forest ManagementClimate Change, Forests and Forest Management 69

Figure 6.6 - Insects such as the pine caterpillar, Dendrolimus punctatus, a destructive defoliator of tropical pines in Southeast Asia, can undergo additional generations in warmer climates.


polymorpha in the Hawaiian Islands, USA, Azadirachta indicain the Sahel region of Africa, Acacia nilotica in the Sudan andEucalyptus spp in Australia and South America (Ciesla andDonaubauer 1994).

Widening carbon/nitrogen ratios in trees due toelevated levels of CO2 could increase foliageconsumption by insects as has beendemonstrated in laboratory studies. Forexample, Lincoln et al (1984) showed thatfeeding rates of lepidopterous larvae rose withcorresponding increases in atmospheric CO2.Forest defoliators such as the sprucebudworms, Choristoneura spp., in NorthAmerica and pine caterpillars, Dendrolimus spp.in Asia could be similarly affected. As a resultoutbreaks could cause more severe defoliation.More recently Lincoln (1993) showed similarfeeding responses from larvae representinganother group of foliage feeding insects; pinesawflies, Neodiprion sp. (Hymenoptera:Diprionidae).

A higher incidence of insect and diseaseoutbreaks due to stress on trees associatedwith climate change will result in higher levelsof combustible fuels in forests increasing therisk of wildfires. In the conifer forests ofwestern North America, recent outbreaks ofseveral species of bark beetles (FamilyScolytidae) have increased the volumes offlammable fuels to dangerously high levelsThese have resulted in large fires of highintensity including the 1988 fire in YellowstoneNational Park in the USA. These outbreaks arebelieved to be related to fire exclusion and notclimate change, however they serve as anexample of what could happen as a result of


polymorpha in the Hawaiian Islands. USA. Azadirachta indica in the Sahel region of Africa. Acacia nilotica in the Sudan and Eucalyptus spp in Australia and South America (Ciesla and Donaubauer 1994).

*

*

Widening carbon/nitrogen ratios in trees due to elevated levels of CO 2 could increase foliage consumption by insects as has been demonstrated in laboratory studies. For example. Lincoln et al (1984) showed that feeding rates of lepidopterous larvae rose with corresponding increases in atmospheric CO 2 ,

Forest defoliators such as the spruce budworms. Choristoneura spp.. in North America and pine caterpillars, Dendro/imus spp. in Asia could be similarly affected. As a result outbreaks could cause more severe defoliation. More recently Lincoln (1993) showed similar feeding responses from larvae representing another group of foliage feeding insects; pine sawflies. Ne 0 diprion sp. (Hymenoptera: Diprionidae).

A higher incidence of insect and disease outbreaks due to stress on trees associated with climate change will result in higher levels of combustible fuels in forests increasing the risk of wildfires. In the conifer forests of western North America. recent outbreaks of several species of bark beetles (Family Scolytidae) have increased the volumes of flammable fuels to dangerously high levels. These have resulted in large fires of high intensity including the 1988 fire in Yellowstone National Park in the USA. These outbreaks are believed to be related to fire exclusion and not climate change. however they serve as an example of what could happen as a result of


predicted climate change (Hessburg et al 1994,USDA 1994)

Some possible positive effects are:

The higher growth rates which are projected bysome scientists, due to warmer temperaturesand elevated CO2 levels might allow forests tosustain higher levels of insect and diseasedamage without reductions in growth and yield.

The increased vigour of trees and forestsgrowing in elevated CO2 levels could be moreresistant to attack by insects and disease.

Elevated CO2 may benefit plant health andproductivity by altering the morphology andphysiology of plants to the detriment of diseasecausing organisms.

The hazard of destructive insect and disease outbreaks intropical forests is believed to be minimal when compared totemperate and boreal forests because of their inherentdiversity. While this may be true in tropical forests of naturalorigin, it must be kept in mind that many tropical countries, tomeet their needs for wood products, rely on single speciesplantations, often of fast growing exotics. Many of theseplantations are established with material representing a narrowgenetic base. These are often unable to adapt to changingenvironmental conditions. In 1990, there were an estimated30.7 million ha of forest plantations in 90 tropical countries(FAO 1993). A total of 23% were of Eucalyptus spp and 10%were of various species of Pinus. These are subject to attackby a variety of pests, many of which are accidentallyintroduced. An excellent review of forest insect and diseaseplantation pests of the Asia-Pacific Region is provided byHutacharern et al (1990). This review clearly indicates that in


predicted climate change (Hessburg et al 1994, USDA 1994)

Some possible positive effects are:

•

•

•

The higher growth rates which are projected by some scientists, due to warmer temperatures and elevated CO, levels might allow forests to sustain higher levels of insect and disease damage without reductions in growth and yield.

The increased vigour of trees and forests growing in elevated CO, levels could be more resistant to attack by insects and disease.

Elevated CO, may benefit plant health and productivity by altering the morphology and physiology of plants to the detriment of disease causing organisms.

The hazard of destructive insect and disease outbreaks in tropical forests is believed to be minimal when compared to temperate and boreal forests because of their inherent diversity. While this may be true in tropical forests of natural origin, it must be kept in mind that many tropical countries, to meet their needs for wood products, rely on single species plantations, often of fast growing exotics. Many of these plantations are established with material representing a narrow genetic base. These are often unable to adapt to changing environmental conditions. In 1990, there were an estimated 30.7 million ha of forest plantations in 90 tropical countries (FAO 1993). A total of 23% were of Eucalyptus spp and 10% were of various species of Pinus. These are subject to attack by a variety of pests, many of which are accidentally introduced. An excellent review of forest insect and disease plantation pests of the Asia-Pacific Region is provided by Hutacharern et al (1990). This review clearly indicates that in


tropical managed forests, there is an ample number of insectand disease pests which could respond to changes in climate.


tropical managed forests, there is an ample number of insect and disease pests which could respond to changes in climate.


Box 6.2. Dieback of Juaiperus procera inKenya - an example of the effects of aregional climate change?

Die back and mortality of Juniperus procera,an irnportant component of highland forestsin Kenya has been occurring at least sincethe early 1980's. In some places, up to90% of the trees have been affected. Theheaviest dieback and mortality occurs in thedrier low elevation forests. Higher elevationstands, which receive more precipitationand grow on better soils appear to be in areasonably good state of health.

The factors responsible for this conditionare unknown. One hypothesis is that theseforests have been stressed by a long termregional warming and drying trend whichhas affected the low elevation sites to thepoint where they are no longer suitable forthis species (Ciesla et al 1994). As a result,the altitudinal range of this species couldbecome more restricted in the future.


Box 6.2. Dieback of plocers in Kenya - an example of the effects of a regional climate change 7

Dieback and mortality of Juniperus pracera, an important component of highland forests in Kenya has been occurring at least since the early 1980's. In some places, up to 90% of the trees have been affected . The heaviest die back and mortality occurs in the drier low elevation forests. Higher elevation stands, which receive more precipitation anp grow on better soils appear to be in a reasonably good state of health.

The factors responsible for this condition are unknown. One hypothesis is that these forests have been stressed by a long term regional warming and " drying trend which ha~ affected the low elevation sites to the point where they are no longer suitable for this species (Ciesla et al 1994). As a result, the altitudinal range of this species could become more restricted in the future.

73


Chapter 7HELPING FORESTS ADAPT TO CLIMATE CHANGE

37. HOW CAN WE RESPOND TO PREDICTED CLIMATECHANGE?

There are two overall approaches to responding to predictedclimate change; adaptation and mitigation. These approachesapply to all sectors involved in the climate change issue.

ADAPTATION is concerned with responses to the effects ofclimate change. It refers to any adjustment, whether passive,reactive or anticipatory that can be adopted to ameliorate theanticipated expected or actual adverse consequences effectsof climate change. Adaptation also includes taking advantageof any possible beneficial effects such as longer growingseasons which might allow planting of certain crops at higherlatitudes.

Many adaptation policies make good sense regardless ofclimate change because present day climatic variability andextreme climatic events, such as droughts, severe storms andfloods already cause significant damage in most parts of theworld. Adaptation to these events can help reduce damage inthe short term regardless of any long term changes in climate.

MITIGATION or "limitation" attempts to address the causes ofclimate change. It achieves this through actions whichprevent or retard increases in levels of atmospheric GHGs bylimiting current and future emission sources and enhancingpotential sinks of GHGs.

Both adaptation and mitigation strategies should be consideredin an integrated approach when designing responses to climatechange. This chapter addresses opportunities for helpingforests adapt to climate change while Chapter 8 addressesmitigation options.


Chapter 7 HELPING FORESTS ADAPT TO CLIMATE CHANGE

37, HOW CAN WE RESPOND TO PREDICTED CLIMATE CHANGE?

There are two overall approaches to responding to predicted climate change; adaptation and mitigation. These approaches apply to all sectors involved in the climate change issue.

ADAPTA TION is concerned with responses to the effects of climate change. It refers to any adjustment, whether passive, reactive or anticipatory that can be adopted to ameliorate the anticipated expected or actual adverse consequences effects of climate change. Adaptation also includes taking advantage of any possible beneficial effects such as longer growing seasons which might allow planting of certain crops at higher latitudes.

Many adaptation policies make good sense regardless of climate change because present day climatic variability and extreme climatic events, such as droughts, severe storms and floods already cause significant damage in most parts of the world. Adaptation to these events can help reduce damage in the short term regardless of any long term changes in climate.

MITlGA TION or "limitation" attempts to address the causes of climate change . It achieves this through actions which prevent or retard increases in levels of atmospheric GHGs by limiting current and future emission sources and enhancing potential sinks of GHGs.

Both adaptation and mitigation strategies should be considered in an integrated approach when designing responses to climate change. This chapter addresses opportunities for helping forests adapt to climate change while Chapter 8 addresses mitigation options.


DO NATURAL PROCESSES EXIST WHICH CAN HELPTREES AND FORESTS ADAPT TO A CHANGINGCLIMA TE?

Some populations of trees, because of their genetic variability,will be able to survive the effects of climate change byadjusting to the new conditions through acclimation ratherthan by migrating to new locations with climates similar to theoriginal habitat. Another potential adaptive mechanism is thatcertain physiological and developmental traits will undergopermanent changes as a result of evolution.

In many cases, the boundaries of a species' range may be aconsequence of factors operating in addition to climate. Oneof these factors is competition. In the northern hemisphere,the southern limits or lower elevation limits of the ranges ofmany species are determined by competitive relationships withspecies to the south or at lower elevations. Thus, manynorthern species grow quite well in non-competitive situationsfar south of their natural ranges. If climate changes, thesespecies may be able to persist in their original locations if thebetter competitors do not invade immediately.

Often, reproduction and seedling establishment is moresensitive to climate change than is the survival of matureindividuals. In such cases, adult individuals may persist in anarea long after regeneration has disappeared.

HOW CAN FOREST MANAGEMENT HELP FORESTSADAPT TO CLIMA TE CHANGE?

Good silvicultural practices, including maintenance of optimumstocking levels and selection of trees which are best adaptedto existing sites should ensure that forests remain vigorousand relatively free of site and stand related stress. Thesepractices should help forests adapt to climate change.


38, DO NA TURAL PROCESSES EXIST WHICH CAN HELP TREES AND FORESTS ADAPT TO A CHANGING CLIMATE?

Some populations of trees, because of their genetic variability, will be able to survive the effects of climate change by adjusting to the new conditions through acclimation rather than by migrating to new locations with climates similar to the original habitat. Another potential adaptive mechanism is t hat certain physiological and developmental traits will undergo permanent changes as a result of evolution.

In many cases, the boundaries of a species' range may be a consequence of factors operating in addition to climate . One of these factors is competition . In the northern hemisphere, the southern limits or lower elevation limits of the ranges of many species are determined by competitive relationships with species to the south or at lower elevations. Thus, many northern species grow quite well in non-competitive situations far south ot their natural ranges. If climate changes, these species may be able to persist in their original locations if the better competitors do not invade immediately.

Often, reproduction and seedling establishment is more sensitive to climate change than is the survival of mature individuals. In such cases, adult individuals may persist in an area long after regeneration has disappeared.

39. HOW CAN FOREST MANAGEMENT HELP FORESTS ADAPT TO CLlMA TE CHANGE?

Good silvicultural practices, including maintenance of optimum stocking levels and selection of trees which are best adapted to existing sites should ensure that forests remain vigorous and relatively free of site and stand related stress. These practices should help forests adapt to climate change.


feasible in mixed species plantings, which arewell adapted to local sites and climaticconditions and meet national needs for forestproducts and services.

Establish in-situ and ex-situ reserves of keyforest species to ensure that a gene pool ofsufficient variability is available for treeimprovement programmes which have theobjective of developing varieties capable ofadapting to climate change.

Accelerate timber salvage and fuel managementprogrammes to reduce the hazard of wildfire inforests, especially those which have sufferedfrom high levels of pest and disease damage orforest decline events.

Design insect and disease monitoringprogrammes which are capable of detectingincreases in the occurrence and intensity offorest decline events and in the activity of newpests and diseases (both indigenous andintroduced) in addition to those which havehistorically caused losses. Monitoring systemsshould also be capable of detecting changes inthe biology, ecology and natural ranges of pestspecies including timing of key events in theirlife histories, number of generations, feedingpatterns and pest/host interactions.

Initiate research programmes to determineeffects of long term climate change on thebiology and pest-disease/host interactions oftraditional pest species. In addition, identifythose species which have a potential forbecoming pests under a climate change

78

•

•

•

•


feasible in mixed species plantings, which are well adapted to local sites and climatic conditions and meet national needs for forest products and services.

Establish in-situ and ex-situ reserves of key forest species to ensure that a gene pool of sufficient variability is available for tree improvement programmes which have the objective· of developing varieties capable of adapting to climate change.

Accelerate timber salvage and fuel management programmes to reduce the hazard of wildfire in forests, especially those which have suffered from high levels of pest and disease damage or forest decline events.

Design insect and disease monitoring programmes which are capable of detecting increases in the occurrence and intensity of forest decline events and in the activity of new pests and diseases (both indigenous and introduced) in addition to those which have historically caused losses. Monitoring systems should also be capable of detecting changes in the biology, ecology and natural ranges of pest species including timing of key events in their life histories, number of generations, feeding patterns and pest/host interactions.

Initiate research programmes to determine effects of long term climate change on the biology and pest-disease/host interactions of traditional pest species. In addition, identify those species which have a potential for becoming pests under a climate change


scenario. Integrate new research informationinto operating programmes as soon as possible.

Conduct studies on the effects of fire, insectsand disease on biodiversity in terms ofcolonizers, successional and climax species.Determine the degree of "disruptions" in the selfrepairing process of vegetation systems due toclimate change. Examples include the inabilityof forests to re-invade burned or harvestedareas, or an "arrested" succession, where scrubor liana vegetation is no longer replaced byforest.

Initiate studies to determine the effects ofclimatic anomalies on forest stability.


•

•

scenario. Integrate new research information into operating programmes as soon as possible.

Conduct studies on the effects of fire, insects and disease on biodiversity in terms of colonizers, successional and climax species. Determine the degree of "disruptions" in the self repairing process of vegetation systems due to climate change. Examples include the inability of forests to re-invade burned or harvested areas, or an "arrested" succession, where scrub or liana vegetation is no longer replaced by forest .

Initiate studies to determine the effects of climatic anomalies on forest stability.


CHAPTER 8THE ROLE OF FORESTS AND FORESTRY FOR

MITIGATING THE EFFECTS OF CLIMATE CHANGE

41. WHAT OPPORTUNITIES DO FORESTS AND FORESTMANAGEMENT OFFER FOR MITIGATING THEEFFECTS OF PREDICTED CLIMA TE CHANGE?

Forests provide opportunities to partially mitigate the predictedeffects of climate change. This can be accomplished throughthree overall approaches:

Reducing sources of greenhouse gases.

Maintaining existing sinks of greenhouse gases.

Expanding sinks of greenhouse gases.

Specific actions under each of these approaches are describedin sections 8A - 8C of this chapter.

Two things must be kept in mind when planning forest sectorstrategies and programmes designed to mitigate effects ofclimate change:

Trees and forests are only temporary carbon sinks.When trees are harvested, burned or die, some of thestored carbon is again released into the atmosphere.Forest sector policies and strategies therefore shouldaim at prolonging the carbon storage capacity of treesand forests as long as possible.

Any forest sector mitigation measures must be done inconcert with mitigation measures in other sectors thatcontribute significantly to the build up of GHGs in theatmosphere such as industry, agriculture,transportation and power generation.


CHAPTER 8 THE ROLE OF FORESTS AND FORESTRY FOR

MITIGATING THE EFFECTS OF CLIMATE CHANGE

41, WHAT OPPORTUNITIES DO FORESTS AND FOREST MANA GEMENT OFFER FOR MITIGA TING THE EFFECTS OF PREDICTED CL/MA TE CHANGE?

Forests provide opportunities to partially mitigate the predicted effects of climate change. This can be accomplished through three overall approaches:

Reducing sources of greenhouse gases.

Maintaining existing sinks of greenhouse gases.

Expanding sinks of greenhouse gases,

Specific actions under each of these approaches are described in sections SA - SC of this chapter.

Two things must be kept in mind when planning forest sector strategies and programmes designed to mitigate effects of climate change:

•

•

Trees and forests are only temporary carbon sinks . When trees are harvested, burned or die, some of the stored carbon is again released into the atmosphere. Forest sector policies and strategies therefore should aim at prolonging the carbon storage capacity of trees and forests as long as possible.

Any forest sector mitigation measures must be done in concert with mitigation measures in other sectors that contribute significantly to the build up of GHGs in the atmosphere such as industry, agriculture, transportation and power generation.


WHAT FEATURES SHOULD CHARACTERIZE ACTIONSTAKEN TO MITIGA TE POTENTIAL EFFECTS OFCLIMA TE CHANGE?

Regardless of what actions are taken to mitigate the predictedaffects of climate change, they should have the followingcharacteristics:

Ecologically Sustainable - Actions should provide forthe long term needs of both present and futuregenerations.

Economically Viable - Proposed actions should havelow start up costs and be socially integrative, buildingon local needs, life styles and traditions.

Technologically Simple - Actions should be capable ofbeing implemented successfully under a variety ofconditions with a minimum of specialized equipment,training or procedures.

Adaptable - They should have sufficient flexibility toadapt to changing economic, political, social, ecologicaland climatic conditions.

Socially Acceptable - Proposed actions should haveimmediate and clear benefits, especially to localresidents.

WHAT ADDITIONAL RESEARCH IS NEEDED TO MOREFULL Y UNDERSTAND THE POTENTIAL EFFECTS OFCLIMA TE CHANGE ON TREES AND FORESTS AND TODEVELOP ADAPTATION AND MITIGATION TACTICS?

There are many uncertainties associated with all aspects of theglobal climate change issue. With regard to forests and


42. WHA T FEA TURES SHOULD CHARACTERIZE ACTIONS TAKEN TO MITIGATE POTENTIAL EFFECTS OF CL/MA TE CHANGE?

Regardless of what actions are taken to mitigate the predicted affects of climate change, they should have the following characteristics:

Ecologically Sustainable - Actions should provide for the long term needs of both present and future generations.

Economically Viable - Proposed actions should have low start up costs and be socially integrative, building on local needs, life styles and traditions.

Technologically Simple - Actions should be capable of being implemented successfully under a variety of conditions with a minimum of specialized equipment, training or procedures.

Adaptable - They should have sufficient flexibility to adaptto changing economic, political, social, ecological and climatic conditions.

Socially Acceptable - Proposed actions should have immediate and clear benefits, especially to local residents.

43. WHA T ADDITIONAL RESEARCH IS NEEDED TO MORE FULL Y UNDERSTAND THE POTENTIAL EFFECTS OF CL/MA TE CHANGE ON TREES AND FORESTS AND TO DEVELOPADAPTA TION AND MITIGATION TACTICS?

There are many uncertainties associated with all aspects of the global climate change issue. With regard to forests and


forestry there are uncertainties concerning the impact ofpossible climate change on forest ecosystems, the adaptationof forests to climate change and the potential for mitigatingpredicted adverse effects of climate change by forests.

During a Ministerial Conference on the Protection of Forests inEurope held in Helsinki, Finland in 1993, the European statesand the European Union agreed to a programme of intensifiedresearch and cooperation on forestry and climate change. Thisprogramme provides a comprehensive model for national and(or) regional efforts and recommends the following lines ofinvestigation:

Achieve a greater understanding of the linkagesbetween climate change and forest ecosystems,including feed-backs from ecosystems to theclimate system.

Quantify the role of forests, forest soils andpeatlands as reservoirs, sinks and sources ofcarbon and understand the role of forests in theglobal carbon cycle. Research in this field mayinclude the development of commonmethodologies for research, for national andregional inventories and the development andmaintenance of data bases on reservoirs, sinksand sources of carbon in terrestrial ecosystems.

Identify the genetic variability associated withregionally important tree species and their abilityto respond to changes in climate and increasedconcentration of carbon dioxide, and on thedegree and rate of evolutionary processes andadaptation.

Determine the dynamic equilibrium of host-parasite relationships in new climaticenvironments.


forestry there are uncertainties concerning the impact of possible climate change on forest ecosystems, the adaptation of forests to climate change and the potential for mitigating predicted adverse effects of climate change by forests.

During a Ministerial Conference on the Protection of Forests in Europe held in Helsinki, Finland in 1993, the European states and the European Union agreed to a programme of intensified research and cooperation on forestry and climate change. This programme provides a comprehensive model for national and (or) regional efforts and recommends the following lines of investigation:

*

*

*

*

Achieve a greater understanding of the linkages between climate change and forest ecosystems, including feed-backs from ecosystems to the climate system.

Quantify the role of forests, forest soils and peatlands as reservoirs, sinks and sources of carbon and understand the role of forests in the global carbon cycle. Research in this field may include the development of common methodologies for research, for national and regional inventories and the development and maintenance of data bases on reservoirs, sinks and sources of carbon in terrestrial ecosystems.

Identify the genetic variability associated with regionally important tree species and their ability to respond to changes in climate and increased concentration of carbon dioxide, and on the degree and rate of evolutionary processes and adaptation.

Determine the dynamic equilibrium of hostparasite relationships in new climatic environments.


Study changes in soil formation processes,including the mineralisation of organic matterand leaching, in response to climate change.

Develop process-based predictive ecosystemmodels applicable on a regional scale which maybe used in to integrate anticipated changes inclimate, interactions with air pollution, effectson forest ecosystems, fluxes of greenhousegases and effects on forests and forestmanagement.

Define ways to alter forest managementsystems to optimise adaptation to climatechange, ensure the health and functions offorests and to optimise the sequestration andstorage of carbon.

A conceptual plan for research in forest/atmosphericinteractions in the United States has also been designed byUSDA Forest Service (USDA 1988).

44. DO INTERNATIONAL AGREEMENTS EXIST WHICHENCOURAGE DEVELOPMENT AND PROTECTION OFFORESTS TO ENHANCE THEIR ABILITY TO MITIGA TETHE EFFECTS OF CLIMATE CHANGE?

Several international instruments and targets have beendeveloped which support large scale forest sector developmentas a means of mitigating the effects of predicted climatechange.

One of the first international accords on climate change whichreferred directly to forestry was the Nordwijk Declaration onClimate Change which was developed in 1989. Thisdeclaration established a target of a net growth in forest areaof 12 million ha/yr by the beginning of the next century. A


•

•

•

Study changes in soil formation processes, including the mineralisation of organic matter and leaching, in response to climate change.

Develop process-based predictive ecosystem models applicable on a regional scale which may be used in to integrate anticipated changes in climate, interactions with air pollution, effects on forest ecosystems, fluxes of greenhouse gases and effects on forests and forest management.

Define ways to alter forest management systems to optimise adaptation to climate change, ensure the health and functions of forests and to optimise the sequestration and storage of carbon.

A conceptual plan for research in forest/atmospheric interactions in the United States has also been designed by USDA Forest Service (USDA 1 988).

44. DO INTERNATIONAL AGREEMENTS EXIST WHICH ENCOURAGE DEVELOPMt;NT AND PROTECTION OF FORESTS TO ENHANCE THEIR ABILITY TO MITlGA TE THE EFFECTS OF CLlMA TE CHANGE?

Several international instruments and targets have been developed which support large scale forest sector development as a means of mitigating the effects of predicted climate change.

One of the first international accords on climate change which referred directly to forestry was the Nordwijk Declaration on Climate Change which was developed in 1989. This declaration established a target of a net growth in forest area of 12 million ha/yr by the beginning of the next century. A


follow up workshop held in Bangkok, Thailand in 1991concluded that the prospect for attaining such a target wasvery limited (IPCC 1992).

During the United Nations Conference on Environment andDevelopment (UNCED), held in Rio de Janiero, Brazil, aFramework Convention on Climate Change, designed tocontrol and reduce future GHG emissions was signed. Thisconvention was ratified by 100 signatory countries byDecember 1994.

A non-legally binding authoritative statement entitled"Principles for a Global Consensus on the Management,Conservation and Sustainable Development of all Types ofForests" was adopted at the UNCED conference. Thestatement stresses that forest lands should be sustainablymanaged to meet the social, economic, ecological, cultural andspiritual human needs of present and future generations.These principles and Agenda 21, an environmental programmefor the 21st century which was also promulgated at UNCED,propose forest conservation measures to conserve carbonpools and increase the security of these pools.

These statements which must be translated into actionprogrammes at the country and community level in order to beimplemented. Several countries, including China, Denmark,Finland, France and Italy have developed strategic action plansunder the umbrella of these international agreements. France,for example, has targeted the addition of 30 000 ha ofafforestation annually for the next 50 years and the promotionof more durable uses of wood (e.g. in construction) (Ministèrede l'Agriculture et de la Pbche 1994).

International agencies, such as FAO, can provide a wide rangeof technical assistance and training related to climate changeand identification of opportunities for forests to mitigate itseffects.


follow up workshop held in Bangkok, Thailand in 1991 concluded that the prospect for attaining such a target was very limited (lPCC 1992).

During the United Nations Conference on Environment and Development (UNCEDL held in Rio de Janiero, Brazil, a Framework Convention on Climate Change, designed to control and reduce future GHG emissions was signed. This convention was ratified by 100 signatory countries by December 1994.

A non-legally binding authoritative statement entitled "Principles for a Global Consensus on the Management, Conservation and Sustainable Development of all Types of Forests" was adopted at the UNCED conference. The statement stresses that forest lands should be sustainably managed to meet the social, economic, ecological, cultural and spiritual human needs of present and future generations. These principles and Agenda 21 , an environmental programme for the 21 st century which was also promulgated at UNCED, propose forest conservation measures to conserve carbon pools and increase the security of these pools.

These statements which must be translated into action programmes at the country and community level in order to be implemented. Several countries, including China, Denmark, Finland, France and Italy have developed strategic action plans under the umbrella of these international agreements. France, for example, has targeted the addition of 30 000 ha of afforestation annually for the next 50 years and the promotion of more durable uses of wood (e.g . in construction) (Ministere de l'Agriculture et de la Peche 1994).

International agencies, such as FAO, can provide a wide range of technical assistance and training related to climate change and identification of opportunities for forests to mitigate its effects.


45. HOW CAN THE TROPICAL FORESTS ACTIONPROGRAMME (TFAP) ASSIST IN DEVELOPING FORESTSECTOR PROGRAMMES TO HELP MITIGA TE EFFECTSOF CLIMA TE CHANGE?

TFAP is designed to assist countries in the conservation andsustainable use of tropical forest resources. The plan grewout of parallel efforts sponsored by FAO, The World Bank(WB), the United Nations Development Programme (UNDP) andthe World Resources Institute (WRI). The Programme wasformalized in 1987 and strengthened in 1991. Leadership forthe programme is housed in FAO.

TFAP is a country-driven approach to forest resource planningand management. The process involves a high level ofparticipation by local people and non-governmentorganisations, is multidisciplinary and intersectorial. TFAPbegins with the formulation or revision of a long term forestpolicy and strategy and the development of a national forestplan. This process can facilitate the integration of clinnatechange considerations into the development andimplementation of long range forest sector policies, strategiesand plans.


45. HOW CAN THE TROPICAL FORESTS ACTION PROGRAMME (TFAP) ASSIST IN DEVELOPING FOREST SECTOR PROGRAMMES TO HELP MITIGA TE EFFECTS OF CL/MA TE CHANGE?

TFAP is designed to assist countries in the conservation and sustainable use of tropical forest resources. The plan grew out of parallel efforts sponsored by FAO. The World Bank (WB). the United Nations Development Programme (UNDP) and the World Resources Institute (WRll. The Programme was formalized in 1987 and strengthened in 1991. Leadership for the programme is housed in FAO.

TFAP is a country-driven approach to forest resource planning and management. The process involves a high level of participation by local people and non-government organisations, is multidisciplinary and intersectorial. TFAP begins with the formulation or revision of a long term forest policy and strategy and the development of a national forest plan. This process can facilitate the integration of climate change considerations into the development and implementation of long range forest sector policies, strategies and plans.


8AREDUCING SOURCES OF GREENHOUSE GASES

46. WHAT ACTIONS CAN BE TAKEN TO REDUCE THECURRENT RATES OF TROPICAL DEFORESTATIONAND HOW MIGHT THIS AFFECT EMISSIONS OF GHGSFROM FORESTS?

Arresting the current rates of deforestation requires actionswhich reduce pressures to convert forest lands to other usesand to protect remaining forests so that they can be managedon a sustainable basis. Most deforestation is caused by theexpansion of agriculture. This is in direct response toexpanding human populations and economic development.Programmes aimed at reducing deforestation must, therefore,be accompanied by efforts to increase productivity andsustainability of existing agricultural lands so that productionkeeps pace with increasing demands. In many cases,deforestation has been considered as being only a forestsector problem when in reality it is a multisectoral issue.

According to one estimate, as much as 80% of forest clearingfor shifting and sedentary agriculture can be eliminated bysubstituting sustainable cropping systems (Lashof and Tirpak(1989). They suggest the following actions for reducing theexpansion of agriculture into tropical forests:

* Introduce crop mixes, planting and managementsystems and improved genetic strains of cropsto increase productivity per unit area on existingagricultural lands. In some cases, investment infertilizers, irrigation systems and capital (highinput systems) will be needed to achieveadequate agricultural intensification andsustainability.


8A REDUCING SOURCES OF GREENHOUSE GASES

46. WHAT ACTIONS CAN BE TAKEN TO REDUCE THE CURRENT RA TES OF TROPICAL DEFORESTA TlON AND HOW MIGHT THIS AFFECT EMISSIONS OF GHGS FROM FORESTS?

Arresting the current rates of deforestation requires actions which reduce pressures to convert forest lands to other uses and to protect remaining forests so that they can be managed on a sustainable basis. Most deforestation is caused by the expansion of agriculture . This is in direct response to expanding human populations and economic development. Programmes aimed at reducing deforestation must. therefore. be accompanied by efforts to increase productivity and sustainability of existing agricultural lands so that production keeps pace with increasing demands. In many cases. deforestation has been considered as being only a forest sector problem when in reality it is a multisectoral issue.

According to one estimate , as much as 80% of forest clearing for shifting and sedentary agriculture can be eliminated by substituting sustainable cropping systems (Lashof and Tirpak (1989). They suggest the following actions for reducing the expansion of agriculture into tropical forests:

• Introduce crop mixes, planting and management systems and improved genetic strains of crops to increase productivity per unit area on existing agricultural lands . In some cases. investment in fertilizers, irrigation systems and capital (high input systems) will be needed to achieve adequate agricultural intensification and sustainability.


Conduct research on use of low external inputcropping systems where high inputs are notfeasible.

Develop opportunities for raising of cash cropsas well as subsistence crops so that farmerscan acquire needed cash to invest in fertilizers,irrigation equipment and other technologies.

Intensify management of existing pasture landsto increase site productivity through theintroduction of optimized foraging strategies,fertilization, mechanisation and improvedlivestock management.

Focus agricultural development on sites withadequate non-forest soils such as savannah,pasture and under-utilised crop lands.

The opportunities for implementing these and other optionsshould be determined through the development of strategicland and resource management plans at the national level.

47. WHAT CAN BE DONE TO REDUCE THE FREQUENCYAND SCALE OF FORESTS AND SAVANNAWOODLAND CONSUMED BY BIOMASS BURNING?

Most fires which occur in the savannas and woodlands of thetropics are prescribed or intentional fires. These are set bylocal residents who use fire to clear land, dispose ofagricultural residues, improve the quality of forage forlivestock or to drive game animals. These practices are basedon traditions which are often thousands of years old. Unlessthere are massive changes in agricultural and rangemanagement practices in these countries in the near future,these practices and resultant carbon emissions will continue inthe future.


•

•

•

•

Conduct research on use of low external input cropping systems where high inputs are not feasible.

Develop opportunities for raising of cash crops as well as subsistence crops so that farmers can acquire needed cash to invest in fertilizers, irrigation equipment and other technologies.

Intensify management of existing pasture lands to increase site productivity through the introduction of optimized foraging strategies, fertilization, mechanisation and improved livestock management.

Focus agricultural development on sites with adequate non-forest soils such as savannah, pasture and under-utilised crop lands.

The opportunities for implementing these and other options should be determined through the development of strategic land and resource management plans at the national level.

47. WHA T CAN BE DONE TO REDUCE THE FREQUENCY AND SCALE OF FORESTS AND SAVANNA WOODLAND CONSUMED BY BIOMASS BURNING?

Most fires which occur in the savannas and woodlands of the tropics are prescribed or intentional fires. These are set by local residents who use fire to clear land, dispose of agricultural residues, improve the quality of forage for livestock or to drive game animals. These practices are based on traditions which are often thousands of years old. Unless there are massive changes in agricultural and range management practices in these countries in the near future, these practices and resultant carbon emissions will continue in the future.


Prescribed fires often escape and burn over areas which arenot intended to be burned. The number and area burned bywildfires or unintentional fires can be reduced throughimplementation of integrated fire management programmes.While the primary benefit of these programmes is theprotection of forest and other wildland resources from wildfire,they will also reduce carbon emissions.

The elements of an integrated wildfire managementprogramme include fire prevention, presuppression planning(fire detection, fire danger rating based on local fire weatherand fuel conditions (Fig 8.1), training and equipping of firebrigades) and suppression, the actual fighting of forest andwoodland fires.

Prevention should be directed toward specific groups of peoplewhich cause wildfires. For example, in Indonesia, woodlandsin several national parks are under a high risk of wildfirebecause of agricultural burning by neighbouring farmers. Thiswas one of the target groups identified as part of a projectfunded through the FAO Technical Cooperation Programme(TCP) in wildfire management. The subsequent fire preventionprogramme specifically addressed this group. Another keyaspect of prevention is fuels management. This includesestablishment of fuel breaks in strategic locations and periodicuse of prescribed burning to reduce volumes of combustiblefuels. A relatively simple procedure such as teaching farmershow to construct fire breaks around pastures or fields whichare to be burned can prevent prescribed fires from escapingand burning surrounding forests and woodlands.

When designing wildfire management programmes, it isnecessary to have an understanding of the ecological role ofnatural fires in the areas which are to be protected. In manysemi-arid ecosystems, fire plays a key role in plant succession.Fire exclusion can result in the establishment of morevegetative biomass than the site is capable of carrying. This


Prescribed fires often escape and burn over areas which are not intended to be burned. The number and area burned by wildfires or unintentional fires can be reduced through implementation of integrated fire management programmes. While the primary benefit of these programmes is the protection of forest and other wildland resources from wildfire, they will also reduce carbon emissions.

The elements of an integrated wildfire management programme include fire prevention. presuppression planning (fire detection, fire danger rating based on local fire weather and fuel conditions (Fig 8.1), training and equipping of fire brigades) and suppression. the actual fighting of forest and woodland fires.

Prevention should be directed toward specific groups of people which cause wildfires. For example, in Indonesia. woodlands in several national parks are under a high risk of wildfire because of agricultural burning by neighbouring farmers. This was one of the target groups identified as part of a project funded through the FAO Technical Cooperation Programme (TCP) in wildfire management. The subsequent fire prevention programme specifically addressed this group. Another key aspect of prevention is fuels management. This includes establishment of fuel breaks in strategic locations and periodic use of prescribed burning to reduce volumes of combustible fuels. A relatively simple procedure such as teaching farmers how to construct fire breaks around pastures or fields which are to be burned can prevent prescribed fires from escaping and burning surrounding forests and woodlands.

When designing wildfire management programmes, it is necessary to have an understanding of the ecological role of natural fires in the areas which are to be protected. In many semi·arid ecosystems, fire plays a key role in plant succession. Fire exclusion can result in the establishment of more vegetative biomass than the site is capable of carrying. This

Figure 8.1 - A forester in Mexico's Yucatan Peninsula assessesforest fuels. Knowledge of fuel conditions is an important factor inplanning forest fire management programmes.

89Climate Chango, Forests and Forest ManagementClimate Change, Forests and Forest Management 89

Figure 8.1 - A forester in Mexico's Yucatan Peninsula assesses forest fuels. Knowledge of fuel conditions is an important factor in planning forest fire management programmes.


vegetation subsequently becomes susceptible to attack byinsects, disease and other damaging agents resulting inexcessively high accumulations of combustible fuels.Consequently, when a wildfire does occur after a long periodof fire exclusion, it burns with greater intensity and can bemore damaging (Hessburg et al 1994, USDA 1994).

48. HOW CAN INCREASING THE EFFICIENCY OF BURNINGFUEL WOOD AND OTHER BIOFUELS REDUCEEMISSIONS OF GHGS?

Fuelwood and other biofuels, including charcoal, crop residues,animal dung and other forms of biomass are used in manyparts of the world for cooking, heating and processing of rawmaterials at the household level (Fig 8.2). Biofuels arepresently the fourth most important source of energy in theworld with fuelwood and charcoal consumption aloneaccounting for 10% of overall world energy consumption. Indeveloping countries, biomass is the dominant energy source.For example, in Ethiopia, biofuels account for over 93% of thenational energy supply (Karekezi 1 994). Use of householdbiofuels is estimated to contribute between 2 and 7% of theannual emissions of GHGs from human sources. Fuelwoodand other biofuels are also used in many developing countriesto support many small and medium scale rural industries suchas charcoal kilns, bakery ovens, brick kilns, tobacco and coffeeprocessing plants.

In most cases, household biofuels are converted into energyusing methods which are inefficient and produce a low energyoutput. They also produce a high GHG output per unit ofenergy produced. The use of more efficient combustionsystems provides an opportunity to increase energy output andreduce the per unit output of GHGs. They provide an addedbenefit of reduced pressure on existing biofuel resources. Thisis especially important in many semi-arid regions where rapidly


vegetation subsequently becomes susceptible to attack by insects, disease and other damaging agents resulting in excessively high accumulations of combustible fuels. Consequently, when a wildfire does occur after a long period of fire exclusion, it burns with greater intensity and can be more damaging (Hessburg et al 1994, USDA 1994).

48. HOW CAN INCREASING THE EFFICIENCY OF BURNING FUEL WOOD AND OTHER BIOFUELS REDUCE EMISSIONS OF GHGS?

Fuelwood and other biofuels, including charcoal, crop residues, animal dung and other forms of biomass are used in many parts of the world for cooking, heating and processing of raw materials at the household level (Fig 8.2) . Biofuels are presently the fourth most important source of energy in the world with fuel wood and charcoal consumption alone accounting for 10% of overall world energy consumption. In developing countries, biomass is the dominant energy source. For example, in Ethiopia, biofuels account for over 93% of the national energy supply (Karekezi 1994). Use of household biofuels is estimated to contribute between 2 and 7% of the annual emissions of GHGs from human sources. Fuelwood and other biofuels are also used in many developing countries to support many small and medium scale rural industries such as charcoal kilns, bakery ovens, brick kilns, tobacco and coffee processing plants.

In most cases, household biofuels are converted into energy using methods which are inefficient and produce a low energy output. They also produce a high GHG output per unit of energy produced. The use of more efficient combustion systems provides an opportunity to increase energy output and reduce the per unit output of GHGs. They provide an added benefit of reduced pressure on existing biofuel resources. This is especially important in many semi-arid regions where rapidly

Figure 8.2 - Fuelvvood is taken from a forest plantation to a villagein Indonesia. Rural people in developing countries rely heavily onfuelwood for cooking and heating. More efficient use of biofuelsoffers another opportunity to reduce GHG emissions.

91Climate Change, Forests and Forest ManagementClimate Change, Forests and Forest Management 91

Figure 8.2 - Fuelwood is taken from a forest plantation 10 a village in Indonesia. Rural people in developing countries rely heavily on fuel wood for cooking and heating. More efficient use of biofuels offers another opportunity to reduce GHG emissions.


expanding populations are putting increased pressure onbiofuel resources, leading to deforestation and desertification.

The introduction of more efficient cooking stoves andindustrial processes could reduce fuelwood requirements by25-70% at a low investment cost. This can also contribute toreduced GHG emissions. In addition, the use of better qualitybiomass in terms of size, moisture content and heating value,if available, can contribute to heating efficiencies and reducedGHG output. In order to achieve maximum benefits from moreenergy efficient technologies, their introduction must beaccompanied by adequate training in their use such asprogrammes which are offered by NGO's such as theFoundation for Woodstove Dissemination.

49. HOW CAN USE OF WOOD AND OTHER "BIOFUELS"IN PLACE OF FOSSIL FUELS HELP REDUCE LEVELS OFGHGS IN THE ATMOSPHERE?

The substitution of biomass in place of fossil fuels as amodern energy source has the potential to dramatically changethe global warming implications of rising energy consumption,especially in tropical countries. Opportunities exist to uselarge quantities of agricultural and forest residues that wouldotherwise go to waste. There are also opportunities todevelop biomass crops primarily for energy production. Ifproduced efficiently, "biofuels" could supply a significantproportion of commercial energy demand in coming decades.

The benefits of bioenergy utilization go beyond substitution offuel sources. Biofuels can not only help to close the CO2 cycleand reduce GHG emissions, but biomass plantations,established on presently fallow lands, would also expandcarbon reservoirs. In addition, the substitution of domesticallyproduced biomass could also contribute to improve the balanceof payments of energy poor countries. Other benefits include


expanding populations are putting increased pressure on biofuel resources, leading to deforestation and desertification.

The introduction of more efficient cooking stoves and industrial processes could reduce fuelwood requirements by 25-70% at a low investment cost. This can also contribute to reduced GHG emissions. In addition, the use of better quality biomass in terms of size, moisture content and heating value, if available, can contribute to heating efficiencies and reduced GHG output. In order to achieve maximum benefits from more energy efficient technologies, their introduction must be accompanied by adequate training in their use such as programmes which are offered by NGO's such as the Foundation for Woodstove Dissemination.

49. HOW CAN USE OF WOOD AND OTHER HBIOFUELSH IN PLACE OF FOSSIL FUELS HELP REDUCE LEVELS OF GHGS IN THE ATMOSPHERE?

The substitution of biomass in place of fossil fuels as a modern energy source has the potential to dramatically change the global warming implications of rising energy consumption, especially in tropical countries. Opportunities exist to use large quantities of agricultural and forest residues that would otherwise go to waste. There are also opportunities to develop biomass crops primarily for energy production. If produced efficiently, "biofuels" could supply a significant proportion of commercial energy demand in coming decades.

The benefits of bioenergy utilization go beyond substitution of fuel sources. Biofuels can not only help to close the CO2 cycle and reduce GHG emissions, but biomass plantations, established on presently fallow lands, would also expand carbon reservoirs. In addition, the substitution of domestically produced biomass could also contribute to improve the balance of payments of energy poor countries. Other benefits include


new job opportunities in rural areas and a decentralization ofenergy resources.

The most obvious opportunities for use of biomass for energyinvolve agricultural and industrial wastes. In Indonesia, forexample, large quantities of wood wastes from logging andwood processing operations are piled and burned, used forlandfill or dumped into rivers and the ocean. These materialsare presently considered to be a waste disposal problem ratherthan a source of energy. It is estimated that in Indonesia,wood wastes from sawmills and plywood plants would besufficient to produce 1 000 megawatts of electricity. This isequivalent to 20-30% of the energy presently derived fromfossil fuels. Sugar cane and rice wastes offer similaropportunities. Some agricultural and industrial wastes canalso be incorporated into the soil to increase carbon storage.

The potential for biomass utilization goes beyond the use ofwaste products. Tropical forestry plantations have recordedyields equivalent to more than 15 tons of carbon per ha peryear. Even assuming modest growth rates, these plantationscould make a significant contribution to both energy suppliesand temporary carbon storage if established over large areas(Trexler et al 1992).

50. HOW CAN MORE EFFICIENT TIMBER HARVESTINGREDUCE GHG EMISSIONS FROM FORESTS?

Uncontrolled timber harvesting operations result in excessivesoil disturbance, logging residues and damaged residual trees.This causes increased emissions of CO2 and other GHGs anddecreases the capacity of the residual forest to sequestercarbon (Pinard 1994). Timber harvesting is a damagingprocess, no matter how well planned and carefullyimplemented. However there are certain planning andoperational practices which can be implemented to reduce thedisruption of forest processes.


new job opportunities in rural areas and a decentralization of energy resources.

The most obvious opportunities for use of biomass for energy involve agricultural and industrial wastes. In Indonesia, for example, large quantities of wood wastes from logging and wood processing operations are piled and burned, used for landfill or dumped into rivers and the ocean. These materials are presently considered to be a waste disposal problem rather than a source of energy. It is estimated that in Indonesia, wood wastes from sawmills and plywood plants would be sufficient to produce 1 000 megawatts of electricity. This is equivalent to 20-30% of the energy presently derived from fossil fuels. Sugar cane and rice wastes offer similar opportunities. Some agricultural and industrial wastes can also be incorporated into the soil to increase carbon storage .

The potential for biomass utilization goes beyond the use of waste products. Tropical forestry plantations have recorded yields equivalent to more than 15 tons of carbon per ha per year. Even assuming modest growth rates, these plantations could make a significant contribution to both energy supplies and temporary carbon storage if established over large areas (Trexler et al 1992).

50. HOW CAN MORE EFFICIENT TIMBER HARVESTING REDUCE GHG EMISSIONS FROM FORESTS?

Uncontrolled timber harvesting operations result in excessive soil disturbance, logging residues and damaged residual trees. This causes increased emissions of CO2 and other GHGs and decreases the capacity of the residual forest to sequester carbon (Pinard 1994). Timber harvesting is a damaging process, no matter how well planned and carefully implemented. However there are certain planning and operational practices which can be implemented to reduce the disruption of forest processes.


Good timber harvesting begins with the development of forestmanagement and harvest plans. The forest management planincludes maps and descriptions of areas to be harvested, areasto be protected, contractual information and other generalpolicies. Harvest plans describe in detail the harvestingoperation.

Many of the reductions in logging damage which arecharacteristic of well managed forests are the results ofcareful harvest planning (Dykstra and Heinrich 1992). Theseenvironmental benefits are generally not expensive and mayactually increase the efficiency of the harvesting operation andreduce costs.

Several procedures can significantly reduce logging damage.Pre-felling of vines is often recommended where they bindtrees together to reduce felling damage. Directional felling isrecommended in areas which are to be selectively logged.This will reduce damage to potential future crop trees andfacilitate skidding. Yarding also deserves a great deal ofconsideration because it can cause damage to soils andresidual trees. Exposed soils are subject to erosion andleaching of organic matter including carbon. Yarding damagecan be reduced by restricting bulldozers to designated skidtrails and maximizing log winching distances. Soil damage canbe further minimized by use of yarding systems which movelogs suspended in the air (eg skylines, helicopters andballoons).

Increased utilization of felled trees will result in a reduction ofoverall land area which needs to be logged. A study by FAO(Dykstra 1994) revealed that in several tropical countries, lessthan 50% of the wood in the main stems of tropical treesfelled for harvest is actually utilized. The remainder of themain stem and the other parts of the tree are left in the forestas logging residues. By comparison, the average fraction ofthe main stems utilized in industrial countries is more than78%.


Good timber harvesting begins with the development of forest management and harvest plans. The forest management plan includes maps and descriptions of areas to be harvested, areas to be protected, contractual information and other general policies. Harvest plans describe in detail the harvesting operation.

Many of the reductions in logging damage which are characteristic of well managed forests are the results of careful harvest planning (Dykstra and Heinrich 1992). These environmental benefits are generally not expensive and may actually increase the efficiency of the harvesting operation and reduce costs.

Several procedures can significantly reduce logging damage. Pre-felling of vines is often recommended where they bind trees together to reduce felling damage. Directional felling is recommended in areas which are to be selectively logged. This will reduce damage to potential future crop trees and facilitate skidding. Yarding also deserves a great deal of consideration because it can cause damage to soils and residual trees. Exposed soils are subject to erosion and leaching of organic matter including carbon . Yarding damage can be reduced by restricting bulldozers to designated skid trails and maximizing log winching distances. Soil damage can be further minimized by use of yarding systems which move logs suspended in the air (eg skylines, helicopters and balloons).

Increased utilization of felled trees will result in a reduction of overall land area which needs to be logged. A study by FAO (Dykstra 1994) revealed that in several tropical countries, less than 50% of the wood in the main stems of tropical trees felled for harvest is actually utilized. The remainder of the main stem and the other parts of the tree are left in the forest as logging residues. By comparison, the average fraction of the main stems utilized in industrial countries is more than 78%.


Post harvest practices such as removal of stream crossingswhich impede water flow, proper slash disposal andtreatments to promote vegetation growth in denuded areas willhelp promote recovery of harvested areas (Putz 1994).

An example of the benefits of improved timber harvestingtechniques comes from a study done in dipterocarp forests inSabah, Malaysia (Pinard 1994). Normally, trees over 60 cm indiameter at breast height (dbh) are harvested and skidded tolandings by bulldozers. Approximately 8 to 15 trees per ha areremoved in this manner and up to 75% of the residual treessuffer logging damage. Prior to logging, these forests canstore up to 330 tC/ha. The harvesting operation removesabout 80 tC/ha. Through the use of controlled harvestingtechniques, it has been demonstrated that if damage to theresidual stand can be reduced from 40% to 20%, theadditional amount of carbon remaining in the residual forestafter 10 years could be over 65 tons/ha (Fig 8.3).

Conventional logging

Damagedtrees

Residual

1E1ì

Residualforest forest(120 tonnes Treetops 1185 tonnescarbon/ha)

Timbercarbon/ha)

Reduced-impact logging

Damagedtrees

4111111111111Treetops

4111117mber

Figure 8.3 - A comparison of residual carbon storage betweenconventional and reduced impact logging in Malaysia (Source: Pinard1994)


Post harvest practices such as removal of stream crossings which impede water flow, proper slash disposal and treatments to promote vegetation growth in denuded areas will help promote recovery of harvested areas (Putz 1994).

An example of the benefits of improved timber harvesting techniques comes from a study done in dipterocarp forests in Sabah, Malaysia (Pinard 1994). Normally, trees over 60 cm in diameter at breast height (dbh) are harvested and skidded to landings by bulldozers. Approximately 8 to 15 trees per ha are removed in this manner and up to 75% of the residual trees suffer logging damage. Prior to logging, these forests can store up to 330 tC /ha. The harvesting operation removes about 80 tC/ha. Through the use of controlled harvesting techniques, it has been demonstrated that if damage to the residual stand can be reduced from 40% to 20%, the additional amount of carbon remaining in the residual forest after 10 years could be over 65 tons/ha (Fig 8.3).

Residual forest (120 tonnes ca rbonJha)

Conventional logging

Damaged trees

Residual forest {1 85 tonnes ca rbon/hal

Reduced-impact logging

Figure 8.3 - A comparison of residual carbon storage between conventional and reduced impact logging in Malaysia (Source: Pinard 19941


SBMAINTAINING EXISTING SINKS

OF GREENHOUSE GASES

51. HOW CAN MANAGEMENT AND CONSERVATION OFNATURAL FORESTS ENHANCE THEIR CAPA CITY TOFIX AND STORE CARBON?

Improved management of natural forests can increaseproductivity and carbon storage potential through acceleratedgrowth, maintenance of optimum levels of stocking andprotection from fire, pests and disease (See question 40).There are many opportunities worldwide, to improve themanagement of natural forests. In the tropics, for example, anestimated 137 million ha of logged forests could benefit fromenrichment planting and regeneration because presentselective logging practices have reduced long term productivity(Grainger 1989) (See question 50).

The development and expansion of non-wood forest productswould provide increased incentives to maintain and protectforests. This could have the added desirable effect ofincreased carbon storage. Examples of opportunities todevelop non-wood forest products include production of latex,nuts, resin, mushrooms, wild meat and plants of medicinalvalue (Fig 8.4).

Establishment of reserved or protected forests, which areexcluded from timber harvesting will also help maintainexisting natural forests as carbon sinks, provided that they areprotected from damaging effects of fire, pests and disease.These forests still provide many opportunities for managementof non-timber forest resources. These include providinghabitat for wildlife, establishment of sites where rare orendangered plant species can be protected, in situ


88 MAINTAINING EXISTING SINKS

OF GREENHOUSE GASES

51, HOW CAN MANAGEMENT AND CONSERVATION OF NA TURAL FORESTS ENHANCE THEIR CAPACITY TO FIX AND STORE CARBON?

Improved management of natural forests can increase productivity and carbon storage potential through accelerated growth, maintenance of optimum levels of stocking and protection from fire, pests and disease (See Question -40). There are many opportunities worldwide, to improve the management of natural forests. In the tropics, for example, an estimated 137 million ha of logged forests could benefit from enrichment planting and regeneration because present selective logging practices have reduced long term productivity (Grainger 1989) (See Question 50).

The development and expansion of non-wood forest products would provide increased incentives to maintain and protect forests. This could have the added desirable effect of increased carbon storage. Examples of opportunities to develop non-wood forest products include production of latex, nuts, resin, mushrooms, wild meat and plants of medicinal value (Fig 8.4).

Establishment of reserved or protected forests, which are excluded from timber harvesting will also help maintain existing natural forests as carbon sinks, provided that they are protected from damaging effects of fire, pests and disease. These forests still provide many opportunities for management of non-timber forest resources. These include providing habitat for wildlife, establishment of sites where rare or endangered plant species can be protected, in. situ

Figure 8.4 - In Vietnam, a woman collects resin in a pine plantation.Non-wood forest products can provide economic incentives tomanage and protect forests, thus maintaining their capacity toabsorb and store carbon.

97Climate Change, Forests and Forest ManagementClimate Change, Forests and Forest Management 97

Figure 8.4 - In Vietnam, a woman collects resin in a pine plantation. Non-wood forest products can provide economic incentives to manage and protect forests , thus maintaining their capacity to absorb and store carbon.


conservation of genetic resources, development of outdoorrecreation opportunities, protection of soil and water resourcesand gathering of non-wood products such as wild fruits andmushrooms. Such forests would probably provide a limitedcarbon absorption potential however because they oftencontain large areas of mature forests where carbon absorptionis roughly equal to carbon release.

52. WHAT USES OF FORESTS AND FOREST PRODUCTSARE MOST DESIRABLE FROM THE STANDPOINT OFLONG TERM CARBOIV STORAGE?

From the perspective of CO2 storage, the most desirable usesof forest and forest products are those which extend rotationages and production of goods which are durable and longlasting. This will allow for the carbon to be stored in thewoody tissue for as long as possible. However local andnational needs for goods and services will prevail over globalconcerns for carbon sequestration. Therefore, from the socio-economic standpoint, forests should be put to whatever usesare required to support national and local needs, provided thatthese uses are sustainable. If forests provide for the needs ofpeople, then there are built in incentives to manage them ona sustainable basis and their probability of long term survivaland benefit is increased.

Conversion of trees into durable products such as furniture orwooden structures will extend their carbon sequestration.Recycling of paper products will reduce the need forharvesting trees for manufacture into new paper products.

98 Climate Change; Forests and Forest Management

conservation of genetic resources, development of outdoor recreation opportunities, protection of soil and water resources and gathering of non-wood products such as wild fruits and mushrooms. Such forests would probably provide a limited carbon absorption potential however because they often contain large areas of mature forests where carbon absorption is roughly equal to carbon release.

52. WHA T USES OF FORESTS AND FOREST PRODUCTS ARE MOST DESIRABLE FROM THE STANDPOINT OF LONG TERM CARBON STORAGE?

From the perspective of CO, storage, the most desirable uses of forest and forest products are those which extend rotation ages and production of goods which are durable and long lasting. This will allow for the carbon to be stored in the woody tissue for as long as possible. However local and national needs for goods and services will prevail over global concerns for carbon sequestration. Therefore, from the socioeconomic standpoint, forests should be put to whatever uses are required to support national and local needs, provided that these uses are sustainable. If forests provide for the needs of people, then there are built in incentives to manage them on a sustainable basis and their probability of long term survival and benefit is increased.

Conversion of trees into durable products such as furniture or wooden structures will extend their carbon sequestration. Recycling of paper products will reduce the need for harvesting trees for manufacture into new paper products.

Climate Change, Forests and Forest Management .9.9

ScEXPANDING SINKS OF GREENHOUSE GASES

53. HOW MUCH CARBON CAN BE FIXED IN WOOD ANDSOIL ON A PER HECTARE BASIS IN FORESTPLANTA TIONS IN BOREAL, TEMPERA TE ANDTROPICAL ZONES?

The rate of carbon fixing is a function of many variables.These include tree species, growth rates, longevity, site,annual precipitation, length of growing season, rotation length,etc. Annual rate of carbon fixing is highest in youngplantations.

Fixation rates for several tropical forest plantation species overa given rotation are summarized by Schroeder (1991) (Table8.1).

TABLE 8.1

CARBON FIXATION RATES FOR SEVERALTROPICAL FOREST PLANTATION SPECIES

(Source: Schroeder 1991)

Species Rotation(Yrs)

Mean AboveGround Carbon

Storage(Tonnes C/ha)

Pinus caribeaLeucaena sp.Casuarina sp.Pinus patulaCupressus lusitanicaAcacia nilotica

157-8102020

10-15

5921-4221-55

7257

1 2-17


SC EXPANDING SINKS OF GREENHOUSE GASES

53, HOW MUCH CARBON CAN BE FIXED IN WOOD AND SOIL ON A PER HECTARE BASIS IN FOREST PLANTA TIONS IN BOREAL, TEMPERA TE AND TROPICAL ZONES?

The rate of carbon fixing is a function of many variables. These include tree species, growth rates, longevity, site, annual precipitation, length of growing season, rotation length, etc. Annual rate of carbon fixing is highest in young plantations.

Fixation rates for several tropical forest plantation species over a given rotation are summarized by Schroeder (1991) (Table S.1 ).

TABLE 8.1

CARBON FIXATION RATES FOR SEVERAL TROPICAL FOREST PLANTATION SPECIES

(Source: Schroeder 1991)

Species Rotation Mean Above (Yrs) Ground Carbon

Storage (Tonnes C/ha)

Pinus caribea 15 59 Leucaena sp. 7-8 21-42 Casuarina sp. 10 21 -55 Pinus patula 20 72 Cupressus lusitanica 20 57 Acacia ni/otica 10-15 12-17


An overriding factor in afforestation or reforestation is tomatch the tree species, and provenance to the site on whichit is to be planted. In addition, species should be selectedwhich meet the objectives of the plantation and are acceptableto the people of the locality. If these conditions are met, andwith proper management and protection, t'ne plantationsshould be assured of high rates of survival, good growth andwill meet the objectives for which they are planted, includingsequestration of carbon (Fig 8.5).

54. HOW MUCH ADDITIONAL AREA OF FORESTPLANTA TIONS WOULD BE REQUIRED TO FULLYOFFSET PRESENT ANNUAL INCREASES INGREENHOUSE GAS LEVELS FROM ALL SOURCES?

A number of studies have been conducted to estimate forestarea required to offset various CO2emission goals. A study bySedjo and Solomon (1989) indicates that the current annualincrease in atmospheric carbon could be sequestered for about30 years in approximately 465 million ha of plantation forests.This would require an increase of more than 10% in thecurrent area of forests on the earth's surface. It would alsorepresent an increase of more than four times the presentplantation area in the world. This estimate is based on theassumption of an average annual growth of 15 m3/ha/yr. Anannual growth rate of 5 m3/ha/yr is more realistic forplantations in the boreal and temperate zones and for manytropical areas. Therefore this estimate may be highlyconservative.

Calculations are presented by Grainger (1990) for severalafforestation scenarios. These suggest the following:

* Planting 60 million ha per year for 10 yearswould establish sufficient forest area to absorb2.9 GtC per year, the net increment of CO2from all sources.


An overriding factor in afforestation or reforestation is to match the tree species, and provenance to the site on which it is to be planted. In addition, species should be selected which meet the objectives of the plantation and are acceptable to the people of the locality. If these conditions are met, and with proper management and protection, the plantations should be assured of high rates of survival, good growth and will meet the objectives for which they are planted, including sequestration of carbon (Fig 8.5).

54, HOW MUCH ADDITIONAL AREA OF FOREST PLANTA TIONS WOULD BE REQUIRED TO FULL Y OFFSET PRESENT ANNUAL INCREASES IN GREENHOUSE GAS LEVELS FROM ALL SOURCES?

A number of studies have been conducted to estimate forest area required to offset various CO 2 emission goals. A study by Sedjo and Solomon (1989) indicates that the current annual increase in atmospheric carbon could be sequestered for about 30 years in approximately 465 million ha of plantation forests. This would require an increase of more than 10% in the current area of forests on the earth's surface. It would also represent an increase of more than four times the present plantation area in the world. This estimate is based on the assumption of an average annual growth of 15 m3/ha/yr. An annual growth rate of 5 mJ/ha/yr is more realistic for plantations in the boreal and temperate zones and for many tropical areas. Therefore this estimate may be highly conservative.

Calculations are presented by Grainger (1990) for several afforestation scenarios. These suggest the following:

• Planting 60 million ha per year for 10 years would establish sufficient forest area to absorb 2.9 GtC per year, the net increment of CO2

from all sources.

Figure 8.5 - Plantations of fast growing trees, such as this plantationof Anus radiata in Chile, can absorb atmospheric CO, whileproviding a wide range of wood and non-wood products andservices.

101C//mate Change, Forests and Forest ManagementClimate Change~ Forests and Forest Management 101

Figure 8.5 - Plantations of fast growing trees, such as this plantation of Pinus radiata in Chile , can absorb atmospheric CO2 while providing a wide range of wood and non-wood products and services.


Planting 20 million ha per year beginning in1990 would achieve a carbon absorption equalto the current net annual CO, contribution bythe year 2020.

Planting 2 million ha per year for 30 yearswould establish a forest that could absorb 10%of the net annual increment of CO,.

Continuing the present rate of forest planting forthe next 40 years will offset less than 10% ofthe current net CO2 increase.

Afforestation of 2 to 5 million ha per year couldoffset the CO, emissions from tropical forestsby the year 2020.

The current rate of forest planting in the tropics is about 1.8million ha per year (FAO 1993).

55. TO WHAT EXTENT ARE SUITABLE LANDS AVAILABLEFOR AFFORESTATION AND REFORESTATION?WHERE ARE THEY?

In order to answer this question, the word "suitable" must firstbe qualified. It refers not just to a technical definition in termsof soils and climatic conditions. It also depends on social andeconomic factors. It is possible, at a price, to establish treesalmost anywhere; the cost, however, will be not only inmoney but in human terms, since much of the land that isclassified as "degraded" and available for plantations is in factused by landless people. The decision to commit land area toforest plantations must be technically sound, economicallyfeasible and socially acceptable.

Several estimates of land available for afforestation in thetropics have been made. Grainger (1990) estimates that there

102

•

•

•

•


Planting 20 million ha per year beginning in 1990 would achieve a carbon absorption equal to the current net annual CO, contribution by the year 2020.

Planting 2 million ha per year for 30 years would establish a forest that could absorb 10% of the net annual increment of CO,.

Continuing the present rate of forest planting for the next 40' years will offset less than 10% of the current net CO, increase.

Afforestation of 2 to 5 million ha per year could offset the CO, emissions from tropical forests by the year 2020 .

The current rate of forest planting in the tropics is about 1.8 million ha per year (FAO 1993).

55, TO WHATEXTENTARESUlTABLELANDSAVAILABLE FOR AFFORESTA TlON AND REFORESTA TION? WHERE ARE THEY?

In order to answer this question, the word "suitable" must first be qualified. It refers not just to a technical definition in terms of soils and climatic conditions. It also depends on social and economic factors. It is possible, at a price, to establish trees almost anywhere; the cost, however, will be not only in money but in human terms, since much of the land that is classified as "degraded" and available for plantations is in fact used by landless people. The decision to commit land area to forest plantations must be technically sound, economically feasible and socially acceptable .

Several estimates of land avai lable for afforestation in the tropics have been made. Grainger (1990) estimates that there


may be 621 million ha of land "technically" available. Thisestimate does not take into account socio-econonnicconsiderations. Of this, 418 million ha are in dry, montaneregions and 203 million ha are forest fallow in humid areas.According to Houghton (1990), up to 865 million ha of landare available in the tropics for afforestation. Of this total,there may be about 500 million ha of abandoned lands thatpreviously supported forests in Latin America (100 million ha),Asia (100 million ha) and Africa (300 million ha). Theadditional area would be available only if increases inagricultural productivity on other lands allowed these marginallands to be removed from production. Winjum et al (1992)estimate that a combination of afforestation, agroforestry andforest protection on 300-600 million ha of available land couldconserve and sequester 36-71 Pg C over 50 years.

In the nnid and northern latitudes, land uses have stabilized inmost areas over the past century, however there are stillample opportunities for re/afforestation projects. In sometemperate zone countries, area of forest land has actuallyincreased as marginal agricultural lands which have beenabandoned have reverted to natural forests or have beenreforested. France was 14% forested in 1789 and today 27%of its land area is forested. Within the past 15 yearsapproximately 600 000 ha per year have come out ofagricultural production in Europe, of which about 40% wastransferred to forest and other wooded land (FAO 1992).

In the United States, there are an estimated 46.8 million ha ofcrop and pasture lands which are capable of growing trees andare better suited to this purpose. There are also opportunitiesfor planting of fast growing trees for wood energy productionon 14-28 million ha and establishment of windbreak plantingson 1.37 million ha. If planted, these areas could provide anadditional carbon storage capacity of from 66-210 milliontonnes/yr (Sampson and Hamilton 1992).


may be 621 million ha of land "technically" available. This estimate does not take into account socio-economic considerations. Of this, 41 8 million ha are in dry, montane regions and 203 million ha are forest fallow in humid areas. According to Houghton (1990)' up to 865 million ha of land are available in the tropics for afforestation. Of this total, there may be about 500 million ha of abandoned lands that previously supported forests in Latin America (100 million ha), Asia (100 million ha) and Africa (300 million ha). The additional area would be available only if increases in agricultural productivity on other lands allowed these marginal lands to be removed from production. Winjum et al (1992) estimate that a combination of afforestation, agroforestry and forest protection on 300-600 million ha of available land could conserve and sequester 36-71 Pg Cover 50 years.

In the mid and northern latitudes, land uses have stabilized in most areas over the past century, however there are still ample opportunities for re/afforestation projects. In some temperate zone countries, area of forest land has actually increased as marginal agricultural lands which have been abandoned have reverted to natural forests or have been reforested. France was 14% forested in 1789 and today 27% of its land area is forested. Within the past 15 years approximately 600 000 ha per year have come out of agricultural production in Europe, of which about 40% was transferred to forest and other wooded land (FAO 1992).

In the United States, there are an estimated 46.8 million ha of crop and pasture lands which are capable of growing trees and are better suited to this purpose. There are also opportunities for planting of fast growing trees for wood energy production on 14-28 million ha and establishment of windbreak plantings on 1.37 million ha. If planted, these areas could provide an additional carbon storage capacity of from 66-210 million tonnes/yr (Sampson and Hamilton 1992).


One type of degraded land that may have potential for theestablishment of plantations is salt-affected land, provided itis not used by people who have no other source of land.Reliable and recent estimates of such land are not available butin the tropics there may be over 50 million ha both in Africaand in Asia and over 30 million ha in Latin America as well aslarge areas in Australia and temperate and sub-tropical Asia(Massoud 1977). There are several active researchprogrammes into the selection of salt-tolerant species andprovenances of plantation trees, particularly in Australia andAsia, but it should be noted that there are also researchprogrammes into the development of salt-tolerant agriculturalcrops. Nevertheless salt-affected soils are an important ifunquantified source of land for plantations.

Based on the above information, it would appear that there arelarge areas of suitable land for afforestation and reforestation(in terms of being without encumbrance and with reasonablyfast growth rates) in temperate North America, Europe,Australia, Chile, Argentina, Brazil and Uruguay. In Africa thereare large areas of degraded savanna woodland, but this haslower yield potential and may not be unencumbered. It isimportant to keep in mind, however, that large areas ofplantation may not be the best use of such land, especiallyfrom the standpoint of the needs of the people who presentlyoccupy or use it. Any large scale afforestation or reforestationprojects should be part of a land use plan, made with the fullinvolvement of the people who depend upon the land.

There is also considerable potential for tree planting inhomestead gardens, windbreaks and agroforestry systems(See question 58).


One type of degraded land that may have potential for the establishment of plantations is salt-affected land, provided it is not used by people who have no other source of land. Reliable and recent estimates of such land are not available but in the tropics there may be over 50 million ha both in Africa and in Asia and over 30 million ha -in Latin America as well as large areas in Australia and temperate and sub-tropical Asia (Massoud 1977). There are several active research programmes into the selection of salt-tolerant species and provenances of plantation trees, particularly in Australia and Asia, but it should be noted that there are also research programmes into the development of salt-tolerant agricultural crops. Nevertheless salt-affected soils are an important if un quantified source of land for plantations.

Based on the above information, it would appear that there are large areas of suitable land for afforestation and reforestation (in terms of being without encumbrance and with reasonably fast growth rates) in temperate North America, Europe, Australia, Chile, Argentina, Brazil and Uruguay. In Africa there are large areas of degraded savanna woodland, but this has lower yield potential and may not be unencumbered. It is important to keep in mind, however, that large areas of plantation may not be the best use of such land, especially from the standpoint of the needs of the people who presently occupy or use it. Any large scale afforestation or reforestation projects should be part of a land use plan, made with the full involvement of the people who depend upon the land.

There is also considerable potential for tree planting in homestead gardens, windbreaks and agroforestry systems (See question 58)_


56. WHAT OTHER CONSTRAINTS ARE THERE TO LARGESCALE AFFORESTATION INITIATIVES?

There are several other constraints to large scale afforestationinitiatives in addition to the availability of land. These can beclassified into four general categories; infrastructure, social,economic and ecological constraints.

INFRA STRUCTURE CONSTRAINTS - Limited institutionalcapacity, lack of research on appropriate species to plant,unrealistic government incentives, and soaring populationsrates resulting in increased pressure on available land canconstrain afforestation initiatives.

SOCIAL CONSTRAINTS - The interests and needs of localpeople living in areas proposed for afforestation are ofparamount importance. When goals and objectives of forestryprojects do not coincide with those of the local people, theresults will be less than hoped for. Farmers can easilyperceive government sponsored afforestation or reforestationefforts as an encroachment on customary land use rights andas a challenge to their welfare. Reactions of this nature haveoften led to active opposition and even sabotage throughsetting of intentional fires (Trexler et al 1992).

ECONOMIC CONSTRAINTS - Costs of afforestationprogrammes are highly variable, depending on the nature ofthe terrain to be planted, labour costs, and tree species to beplanted. A rough global estimate indicates that tree plantingcosts can range from a low of SUS 200 to a high of SUS 2000 per ha. Projected socio-economic benefits derived fromplantations may not justify planting costs. (Bernthal 1990).Therefore it would be difficult, if not impossible, for countriesreceiving loans from development banks for afforestationprojects to repay the loans.

ECOLOGICAL CONSTRAINTS - Ecological drawbacks to largeafforestation projects include the potential for introducing low


56, WHA T OTHER CONSTRAINTS ARE THERE TO LARGE SCALE AFFORESTA TION INITIA TIVES?

There are several other constraints to large scale afforestation initiatives in addition to the availability of land. These can be classified into four general categories; infrastructure, social, economic and ecological constraints.

INFRASTRUCTURE CONSTRAINTS . Limited institutional capacity, lack of research on appropriate species to plant, unrealistic government incentives, and 'soaring populations rates resulting in increased pressure on available land can constrain afforestation initiatives .

SOCIAL CONSTRAINTS - The interests and needs of local people living in areas proposed for afforestation are of paramount importance. When goals and objectives of forestry projects do not coincide with those of the local people, the results will be less than hoped for. Farmers can easily perceive government sponsored afforestation or reforestation efforts as an encroachment on customary land use rights and as a challenge to their welfare. Reactions of this nature have often led to active opposition and even sabotage through setting of intentional fires (Trexler et al 1992).

ECONOMIC CONSTRAINTS Costs of afforestation programmes are highly variable; depending on the nature of the terrain to be planted, labour costs, and tree species to be planted. A rough global estimate indicates that tree planting costs can range from a low of $US 200 to a high of $US 2 000 per ha. Projected socio-economic benefits derived from plantations may not justify planting costs. (Bernthal 1990). Therefore it would be difficult, if not impossible, for countries receiving loans from development banks for afforestation projects to repay the loans.

ECOLOGICAL CONSTRAINTS - Ecological drawbacks to large afforestation projects include the potential for introducing low


levels of genetic variability which can characterize large areasof single species plantations. This can reduce their resistanceto site or climate related stress and (or) attack by insects anddisease. Large scale forest plantings can also strain existingwater resources in areas which are already experiencingoverdrafts and escalating demands on ground water resources.

57. WHAT ASSISTANCE IS AVAILABLE TO SUPPORTAFFORESTATION AND REFORESTA TION,PARTICULARL YA T THE INTERNATIONAL LEVEL?

Potential sources of funds include:

National governments.

International and regional development banks.

Forest industry.

International donor agencies, e.g. UNDP.

Bilateral donors.

NG0s.

Private enterprise.

Public utility companies interested in offsettingcarbon emissions

A large number of donors from the developed world, includinginternational agencies, have extended financial support toestablishment of forest plantations in the developing countries.The World Bank has financed forestry projects worth aboutSUS 2.5 billion up to 1990. More than 50% of this amounthas been used for plantation forestry (Pandey 1992). In 1990,development aid for the field of action "management of forests


levels of genetic variability which can characterize large areas of single species plantations. This can reduce their resistance to site or climate related stress and (or) attack by insects and disease. Large scale forest plantings can also strain existing water resources in areas which are already experiencing overdrafts and escalating demands on ground water resources.

57. WHA T ASSISTANCE IS AVAILABLE TO SUPPORT AFFORESTA TlON AND REFORESTA TlON, PARTICULARL Y A T THE INTERNA TIONAL LEVEL?

Potential sources of funds include:

•

•

•

•

•

•

•

•

National governments.

International and regional development banks.

Forest industry.

International donor agencies, e.g. UNDP.

Bilateral donors.

NGOs.

Private enterprise.

Public utility companies interested in offsetting carbon emissions

A large number of donors from the developed world, including international agencies, have extended financial support to establishment of forest plantations in the developing countries. The World Bank has financed forestry projects worth about $US 2.5 billion up to 1990. More than 50% of this amount has been used for plantation forestry (Pandey 1992). In 1990, development aid for the field of action "management of forests


and plantations for industrial use" was SUS 347.6 million or25% of the total. This represents an increase of 1.8 timesfrom the SUS 191.9 million made available in 1988 (Ball1992). It is worth noting, however, that the World Bank andmany bilateral donors are making fewer concessionary loansor grants for industrial roundwood plantations, on the groundsthat they should be profitable enough to seek support fromnormal funding sources.

The Global Environmental Facility (GEF), which is implementedby the World. Bank, UNDP and UNEP, is a funding sourcewhich addresses four key environmental issues. These includereduction of GHG emissions, protection of biodiversity,protection of international waters and reduction in ozone layerdepletion.

Another important component of afforestation andreforestation projects is technical assistance. This is alsoavailable through a number of sources including nationalgovernments, international technical assistance agencies suchas FAO and international donors. An innovative programme toassist rural communities in developing countries to developmore effective strategies, methods and tools for forestryactivities, including tree planting, is the Forests, Trees andPeople Program (FTPP). FTPP operates on the basis of apartnership between a community forestry team in FAO'sForestry Department in Rome and several national and regionalinstitutions in Africa, Asia and Latin America.

58. HOW CAN AGROFORESTRY AND URBAN TREEPLANTINGS CONTRIBUTE TO THE MITIGATION OFCLIMA TE CHANGE?

The magnitude of carbon storage contribution fromagroforestry plantings will depend on the scale at which it isdone and the ultimate use that is made of the wood.


and plantations for industrial use" was $US 347.6 million or 25% of the total. This represents an increase of 1.8 times from the $US 191 .9 million made available in 1988 (Ball 1992) . It is worth noting, however, that the World Bank and many bilateral donors are making fewer concessionary loans or grants for industrial round wood plantations, on the grounds that they should be profitable enough to seek support from normal funding sources.

The Global Environmental Facility (GEFl. which is implemented by the World · Bank, UNDP and UNEP, is a funding source which addresses four key environmental issues. These include reduction of GHG emissions, protection of biodiversity, protection of international waters and reduction in ozone layer depletion.

Another important component of afforestation and reforestation projects is technical assistance. This is also available through a number of sources including national governments, international technical assistance agencies such as FAO and international donors. An innovative programme to assist rural communities in developing countries to develop more effective strategies, methods and tools for forestry activities, including tree planting, is the Forests, Trees and People Program (FTPP). FTPP operates on the basis of a partnership between a community forestry team in FAO's Forestry Department in Rome and several national and regional institutions in Africa, Asia and Latin America.

58. HOW CAN AGROFORESTRY AND URBAN TREE PLANTINGS CONTRIBUTE TO THE MITIGA TION OF CL/MA TE CHANGE?

The magnitude of carbon storage contribution from agroforestry plantings will depend on the scale at which it is done and the ultimate use that is made of the wood.

1 08 Climate Change, Forests and Forest Management

Given suitable economic, social and environmental conditions,farmers have been found to adopt agroforestry systemsreadily. In countries where public forest lands are limited inextent or government tree planting efforts are limited,agroforestry plantings can represent a significant contributionto tree planting and carbon sequestration. There is a potentialfor increased forestry planting both in tropical and temperatezones. Large scale agroforestry tree planting schemes such asthe "Four Around" schemes in China were reportedly carriedout over 6.5 million ha of agricultural lands during the decade1981-1990. A project of this magnitude, if successful, wouldsequester large amounts of carbon as well as providing otherenvironmental benefits such as protection of soil from windand water erosion.

Agroforestry systems are being considered in western Europeas an alternative intensive production systems which arecurrently in place that produce large surpluses of certain crops.In the Unites States, there are large areas which would benefitfrom increased windbreak and shelterbelt plantings (seequestion 55) (Sampson and Hamilton 1992).

Urban tree plantings would provide a more limited carbonstorage benefit than rural plantings because by their nature,they would not be very extensive. However they have thepotential to contribute other benefits in the climate changecontext which are much more significant (Fig 8.6). The effectof urban trees on local microclimates has undergoneinvestigation during the past two decades, largely in developedcountries. It is clear that urban trees have a significant andquantifiable effect on the immediate local climate and therehave been various attempts to estimate what the effect of amajor urban and community tree planting programme might bein the mitigation of carbon emissions. One estimate from theUSA equates the planting of 100 million trees around homes,coupled with an effort to reduce heat absorption and radiation


Given suitable economic, social and environmental conditions, farmers have been found to adopt agroforestry systems readily. In countries where public forest lands are limited in extent or government tree planting efforts are limited, agroforestry plantings can represent-a significant contribution to tree planting and carbon sequestration. There is a potential for increased forestry planting both in tropical and temperate zones . Large scale agroforestry tree planting schemes such as the "Four Around" schemes in China were reportedly carried out over 6.5 million ha of agricultural lands during the decade 1981-1990. A project of this magnitude, if successful, would sequester large amounts of carbon as well as providing other environmental benefits such as protection of soil from wind and water erosion.

Agroforestry systems are being considered in western Europe as an alternative intensive production systems which are currently in place that produce large surpluses of certain crops. In the Unites States. there are large areas which would benefit from increased windbreak and shelterbelt plantings (see question 55) (Sampson and Hamilton 1992).

Urban tree plantings would provide a more limited carbon storage benefit than rural plantings because by their nature, they would not be very extensive. However they have the potential to contribute other benefits in the climate change context which are much more significant (Fig 8.6). The effect of urban trees on local microclimates has undergone investigation during the past two decades, largely in developed countries. It is clear that urban trees have a significant and quantifiable effect on the immediate local climate and there have been various attempts to estimate what the effect of a major urban and community tree planting programme might be in the mitigation of carbon emissions. One estimate from the USA equates the planting of 100 million trees around homes, coupled with an effort to reduce heat absorption and radiation

Figure 8.6 - Shade trees, such as these neems planted along thestreets of Niamey, the capital of Niger, lower temperatures andprovide a more pleasant environment.

through a program of converting dark coloured surfaces, suchas parking lots and buildings to light colours with a reductionof about 17 million tons of carbon from entering theatmosphere each year (Akbari et al 1988). Chinese urbanforesters report that the climate of some cities have beenmarkedly altered through widespread tree planting programmes(see box 8.1).

Trees can also have a significant beneficial effect on the costof winter heating and summer cooling of buildings. Dependingon its location, the energy conservation efforts of a singleurban tree can prevent the release of 15 times moreatmospheric carbon than it is able to sequester. Trees breakup urban "heat islands" by providing shade. The shadeprovided by strategically placed trees per house can reducehome air conditioning needs by 30 to 50%. Trees planted as

C//mate Change, Forests and Forest Management 109Climate Change, Forests and Forest Management 109

Figure 8.6 - Shade trees, such as these neems planted along the streets of Niamey, the capital of Niger, lower temperatures and provide a more pleasant environment.

through a program of converting dark coloured surfaces, such as parking lots and buildings to light colours with a reduction of about 17 million tons of carbon from entering the atmosphere each year (Akbari et al 1988). Chinese urban foresters report that the climate of some cities have been markedly altered through widespread tree planting programmes (see box 8.1).

Trees can also have a significant beneficial effect on the cost of winter heating and summer cooling of buildings. Depending on its location, the energy conservation efforts of a single urban tree can prevent the release of 1 5 times more atmospheric carbon than it is able to sequester. Trees break up urban "heat islands" by providing shade. The shade provided by strategically placed trees per house can reduce home air conditioning needs by 30 to 50%. Trees planted as

1 1 O Climate Change, Forests and Forest Management

windbreaks around buildings in temperate and boreal regionscan reduce winter heating energy use by 4 to 22%. Thereforeurban trees offer a dual benefit of storing small amounts ofcarbon and protecting buildings from extreme hot and coldtemperatures which results in lower consumption of fossilfuels. Urban tree planting may be especially beneficial intropical regions where trees grow rapidly and the direct coolingbenefits of shading are significant (Sampson et al 1992).

The effect of planting trees around buildings for energyconservation is sensitive to the type and shape of the treeinvolved, as well as its location. Deciduous trees that shadewest-facing windows in the summer but allow solar radiationto strike the same windows in winter are especially desirable.In the northern hemisphere, trees on the south side of a houseshould be tall and fairly close to the house, with the lowerboles pruned so that the winter sun can penetrate. For treesto be energy efficient, it is important that species, location andtree management be carefully and properly matched to theindividual situation (Sampson et al 1992).


windbreaks around buildings in temperate and boreal regions can reduce winter heating energy use by 4 to 22%, Therefore urban trees offer a dual benefit of storing small amounts of carbon and protecting buildings from extreme hot and cold temperatures which results in lower consumption of fossil fuels. Urban tree planting may be especially beneficial in tropical regions where trees grow rapidly and the direct cooling benefits of shading are significant (Sampson et al 1992).

The effect of planting trees around buildings for energy conservation is sensitive to the type and shape of the tree involved, as well as its location . Deciduous trees that shade west-facing windows in the summer but allow solar radiation to strike the same windows in winter are especially desirable. In the northern hemisphere, trees on the south side of a house should be tall and fairly close to the house, with the lower boles pruned so that the winter sun can penetrate. For trees to be energy efficient, it is important that species, location and tree management be carefully and properly matched to the individual situation (Sampson et al 1992).


Box 8.1 Effects of tree planting on micro-climate in Nanjing, China

The industrial city of Nanjing, with apopulation of 1.5 million, is known as oneof the five "furnace cities" of the Yangtzevalley. Since 1949, some 3.4 million treeshave been planted in and around the citywith the specific objective of reducingsummer temperatures and generallyregulating the local climate, purifying the airand beautifying the environment. It isclaimed that a drop in average summertemperature from 32.2° C to 29.4°C overthe period 1949 to 1981 is directlyattributable to the cooling effect of treeplanting. Over 32 years, some 23 trees perinhabitant were planted. Tree plantingsinclude block afforestation of degradedhillsides, windbreaks, triple rows of treesalong railways and planting of street trees(Carter 1994).


Box 8.1 Effects of tree planting on microclimate in Nanjing. China

The industrial city of Nanjing.. with a population of 1.5 million. is known as one of the five "furnace cities" of the Yangtze valley. Since 1949. some 3.4 million trees have been planted in and around the city with the specific objective of reducing summer temperatures and generally regulating the local climate. purifying the air and beautifying the environment. It is claimed that a drop in average summer temperature from 32.2° C to 29.4°C over the . period 1949 to 1981 is directly attributable to the cooling effect of tree planting. Over 32 years. some 23 trees per inha~itant were planted. Tree plantings include block afforestation of degraded hillsides. windbreaks. triple rows of trees along ra ilways and planting of street trees (Carter 1994).

111

1 1 2 Climate Change, Forests and Forest Management

59. IS THE PLANTING OF TREES SOLELY FOR CO2ABSORPTIONA SOUND POLICYCONSIDERING OTHERNEEDS FOR AVAILABLE LAND?

There are many uncertainties presently associated with theglobal climate change issue. In addition, in many countries,the amount of land available that is suitable for agriculture and(or) forestry is limited. Therefore, any forest sector responsesto adapt to or mitigate the potential effects of climate changeshould represent sound policy independent of predicted globalwarming and produce net benefits separate from those whichmay ultimately arise in the climate change context (e.g.timber, fuel wood, watershed protection, non wood productsand non commodity values such as ecotourism and recreation).The position of FAO with respect to afforestation for CO2absorption is to encourage tree planting in areas where forestcover is the appropriate vegetation. This should be defined byland use plans and forest strategies as described in documentsprepared under the Tropical Forests Action Plan (TFAP) andnot by theoretical targets (FAO 1990) (see also question 45).

Instead of focusing narrowly on afforestation or reforestation,FAO supports the adoption of an integrated approach whichincludes:

Management and protection of existing areas ofnatural forest to provide for long-term sustainedyield productivity of a wide range of commodityand non-commodity resources including CO2absorption.

Gradually increasing efforts in the afforestationor reforestation of appropriate sites with follow-up management and protection.

Appropriate utilization of the wood produced toreduce the rate of carbon release.


59. IS THE PLANTING OF TREES SOLEL Y FOR CO2

ABSORPTlONA SOUND POLICY CONSIDERING OTHER NEEDS FOR A VAILABLE LAND?

There are many uncertainties presently associated with the global climate change issue. In addition, in many countries, the amount of land available that is suitable for agriculture and . (or) forestry is limited. Therefore, any forest sector responses to adapt to or mitigate the potential effects of climate change should represent sound policy independent of predicted global warming and produce net benefits separate from those which may ultimately arise in the climate change context (e.g. timber, fuel wood, watershed protection, non wood products and non commodity values such as ecotourism and recreation). The position of FAO with respect to afforestation for CO2

absorption is to encourage tree planting in areas where forest cover is the appropriate vegetation. This should be defined by land use plans and forest strategies as described in documents prepared under the Tropical Forests Action Plan (TFAP) and not by theoretical targets (FAO 1990) (see also question 45).

Instead of focusing narrowly on afforestation or reforestation, FAO supports the adoption of an integrated approach which includes:

•

•

•

Management and protection of existing areas of natural forest to provide for long-term sustained yield productivity of a wide range of commodity and non-commodity resources including CO2

absorption.

Gradually increasing efforts in the afforestation or reforestation of appropriate sites with followup management and protection.

Appropriate utilization of the wood produced to reduce the rate of carbon release .


60. WHAT FOREST POLICIES SHOULD BE CONSIDEREDAT THE COUNTRY LEVEL TO ADDRESS THE THREATOF CLIMA TE CHANGE?

A policy aimed at reduction of current levels of deforestationand forest degradation should be of high priority in thosecountries where deforestation is a major activity. Theimplementation of such a policy will require actions in both theforestry and agricultural sector (see question 46). A policy ofafforestation/reforestation is also warranted provided that it iseconomically, ecologically and socially sound, even in theabsence of climate change considerations. Afforestation/reforestation initiatives should be accompanied by policies andprogrammes designed to ensure the health of both plantationsand natural forests so that the objectives of investments madein forest sector development will be met. A policy of partialreplacement of fossil energy sources by wood and otherbiofuels is also worthy of consideration. Use of wood in placeof materials from other sources whose production requiresmany times more energy contributes to energy savings,reduction of GHG emissions and to the maintenance ofexisting carbon reservoirs.

In developing forest sector policies to mitigate the effects ofpredicted global climate change, it must be recognized thatthese can only be done in concert with parallel measures toreduce fossil fuel emissions and to promote sustainableagriculture. Most of the present day contribution ofgreenhouse gases is the result of the burning of fossil fuels.Conservation of fossil fuels and the use of alternative energysources, including the use of renewable energy sources istherefore, essential.


60. WHA T FOREST POLICIES SHOULD BE CONSIDERED A T THE COUNTRY LEVEL TO ADDRESS THE THREA T OF CLlMA TE CHANGE?

A policy aimed at reduction of current levels of deforestation and forest degradation should be of high priority in those countries where deforestation is a major activity. The implementation of such a policy will require actions in both the forestry and agricultural sector (see question 46). A policy of afforestation/reforestation is also warranted provided that it is economically. ecologically and socially sound. even in the absence of climate change considerations. Afforestation/ reforestation initiatives should be accompanied by policies and programmes designed to ensure the health of both plantations and natural forests so that the objectives of investments made in forest sector development will be met. A policy of partial replacement of fossil energy sources by wood and other biofuels is also worthy of consideration. Use of wood in place of materials from other sources whose production requires many times more energy contributes to energy savings. reduction of GHG emissions and to the maintenance of existing carbon reservoirs.

In developing forest sector policies to mitigate the effects of predicted global climate change. it must be recognized that these can only be done in concert with parallel measures to reduce fossil fuel emissions and to promote sustainable agriculture. Most of the present day contribution of greenhouse gases is the result of the burning of fossil fuels. Conservation of fossil fuels and the use of alternative energy sources. including the use of renewable energy sources is therefore. essential.


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Aacid rain-26adaptation-74, 81-83aerosols-25,26afforestation-77,84,100,102-

107,111-113Agenda 21-84agriculture-1,18,22,27,47,53,

54,56,68,80,86,112,113

agroforestry-103,104,107,108air pollution-68,83albedo-9,53alpine plants-60altitude-58,60anomalies-39,68,79anthropogenic-68aquaculture-64asteroid-9,10atmospheric concentration-25atmospheric levels-27,28,59

B

bacteria-46bark beetle-70biofuels-90,91,92,113biomassburning-19,52,53,54,87biomass-19,21,40,41,49,50,52,

53,54,66,67,87,88,90,92,93

boreal forest-60,71brush tire-55burning-1,18,19,21,22,47,53,

54,56,87,88,90,113

Ccarbon absorption-47,49,52,53,

98,102carbon balance-52carbon cycle-2,40,42,44,53,82carbon dioxide-1,13,15,17,18,

19,22,24,28,82carbon exchange-43,48

INDEX

carbon fixing-99carbon monoxide-18,21carbon/nitrogen ratio-70carbon pool-41,84carbon reservoir-49,92,113carbon sequestration-57,98,108carbon sink-40,43,44,49,80,96carbon source-40,43,44,49,

80,96carbon uptake-52,53carbonic acid-13cash crops-87CFC-18,21,24,25CH4-18,19,24,37,46,53charcoal-22,54,90climate prediction models-63climate prediction-63climate zones-58climatic anomalies-39,68,79climatic variability-32,74climax species-79cloud formation-63clouds-9,15,25,26,27,31,

36,60,63CO2-(see carbon dioxide)CO, fertilization effect-34,35,43CO, storage-98coal-54coastal zones-64combustible fuels-67,70,88,90combustion-19,21,90competition-75,76conservation-84,85,96,98,109,

110,113constraints-56continental glaciers-5cooking stoves-92cooling-7,10,11,13,26,60,

109,110,114

Ddeciduous trees-110deep freeze events-68


A acid rain-26 adaptation-74,81 -83 aerosols-25,26 afforestation-77 ,84,100,102-

107,111-113 Agenda 21-84 agriculture-l, 18,22,27,47,53,

54,56,68,80,86,1 12, 113

agroforestry-1 03, 1 04, 1 07,108 air pollution-68,83 albedo-9,53 alpine plants-60 altitude-58,60 anomalies-39,68,79 anthropogenic-68 aquaculture-64

asteroid-9 , 1 ° atmospheric concentration-25 atmospheric levels-27,28,59

B bacteria-46 bark beetle-70 biofuels-90,91 ,92, 113 biomassburning-19,52,53,54,87 biomass-19,21,40,41,49,50,52,

53,54,66,67,87,88, 90,92,93

boreal forest-60,71 brush fire-55 burning-1,18,19,21,22,47,53,

54,56,87,88,90,113

C carbon absorption-47,49,52,53,

98,102 carbon balance-52 carbon cycle-2,40,42,44,53,82 carbon dioxide-l, 13,15,17,18,

19,22,24,28,82 carbon exchange-43,48

INDEX

carbon fixing-99 carbon monoxide-18,21 carbon/nitrogen ratio-70 carbon pool-41 ,84 carbon reservoir-49,92,113 carbon sequestration-57 ,98,108 carbon sink-40,43,44,49,80,96 carbon source-40,43,44,49,

80,96 carbon uptake-52,53 carbonic acid-13 cash crops-a7 CFC-18,21,24,25 CH,-18,19,24,37,46,53 charcoal-22,54,90 climate prediction models-63 climate prediction-63 climate zones-58 climatic anomalies-39,68,79 climatic variability-32,74 climax species-79 cloud formation-63 clouds-9,1 5,25,26,27,31,

36,60,63 CO,-(see carbon dioxide) CO, fertilization effect-34,35.43 CO, storage-98 coal-54 coastal zones-64 combustible fue ls-67, 70,88,90 combustion-19,21,90 competition-75,76 conservation-84,85,96,98,109,

110,113 constraints-56 continental glaciers-5 cooking stoves-92 cooling-7, 1 0, 11,13,26,60,

109,110,114

D deciduous trees- 1 10 deep freeze events-68


defoliation-70defoliator-68,69,70deforestation-18,19,22,43,47,

53,55,56,86,92,113degraded forests-47desert-5,25,35,50desertification-92development-1,10,18,27,56,77,

82,83,84,85,86,87,94,96,98,104,105,106,113

development plans-77donors-106,107drought-8,12,38,39,66,67,68

74

E

ecologically sustainable-81ecologists-65,66economic-30,77,81,84,86,98

105,108economic benefits-105economic constraints-105economic factors-102economic incentives-97economically feasible-102ecosystem-21,47,49,57,59,

60,82,83,88El Niño-9,1 1,12,66elevation-13,47,60,62,65,73,75emissions-11,22,23,25,30,43,47

52,56,86,87,88,90,91,92,93,102,106,107,108,113

ENSO-12,20,66epidemic-67erosion-9,56,64,94,108evapo-transpiration-9,53evaporation-32,33,63evolution-66,75,102extinction-64,65,66

F

FAO-45,84,85,88,94,107,112fire-47,54,55,66,70,76,77

87,88,89,90

fire management-77,88,89fire season-66fisheries-1,27,64fixation rate-99flammable fuels-70flux-40,41,43,83

forest decline-68,78forest ecosystem-47,49,59,82,

83forest fuels-89forest health-67,68,76,77forest industry-106forest management-2,75,76,80,

83,94forest plantation-52,53,71,91,

99,100,102,106forest planting-52,53,71,91

99,100,102,106forest policies-113forest products-54,64,78,96,97

98forest sector-53,68,77,80,83,85

86,112,113forest soil-46,49,56,82,87forestry-1,2,21,27,80,82,83

93,103,104,105,106107,108,112

Forests Trees and PeopleProgramme-107

fossil energy-113fossil fuel emissions-43,52,113fossilfuels-1,18,19,21,22,25,40

47,92,93,110,113fossil pollen-4,58Framework Convention onClimate Change-84

fuel breaks-88fuels-66,67,70,88,89,90fuelwood-90fungi-46


defoliation-70 defoliator-68, 69,70 deforestation-18,19,22,43,47,

53,55,56,86,92,113 degraded forests-47 desert-5,25,35,50 desertification-92 development-1,1 0,18,27,56,77,

82,83,84,85,86,87,94, 96,98,104,105,106,113

development plans-77 donors-l 06,1 07 drought-8,12,38,39,66,67,68

74

E ecologically sustainable-81 ecologists-65,66 economic-30, 77 ,81,84,86,98

105,108 economic benefits-l05 economic constraints-l05 economic factors-l02 economic incentives-97 economically feasible-l02 ecosystem-21,47 ,49,57 ,59,

60,82,83,88 El Nino-9,ll,12,66 elevation-13,47 ,60,62,65, 73, 75 emissions-ll,22,23,25,30,43,47

52,56,86,87,88,90,91, 92,93,102,106,107, 108,113

ENSO-12,20,66 epidemic-67 erosion-9,56,64,94, 108 evapo-transpiration-9,53 evaporation-32, 33, 63 evolution-66, 75,102 extinction-64,65,66

F FAO-45 ,84,85,88,94,107, 112 fire-47 ,54,55,66, 70, 76, 77

87,88,89,90

fire management-77,88,89 fire season-S6 fisheries-1,27,64 fixation rate-99 flammable fuels-70 flux-40,41,43,83

forest decline-68,78 forest ecosystem-47,49,59,82,

83 forest fuels -89 forest health-67,68,76,77 forest industry-106 forest management-2,75,76,80,

83,94 forest plantation-52,53,71,91,

99,100,102,106 forest planting-52,53,71,91

99,100,102,106 forest policies-l1 3 forest products-54,64,78,96,97

98 forest sector-53,68, 77 ,80,83, 85

86,112,113 forest soil-46,49,56,82,87 forestry-1,2,21,27,80,82,83

93 ,1 03,104,105,106 107,108,112

Forests Trees and People Programme-l07

fossil energy-ll 3 fossil fuel emissions-43,52,113 fossil fuels-1, 18,19,21,22,25,40

47,92,93,110,113 fossil pollen-4,58 Framework Convention on Climate Change-84

fuel breaks-88 fuels-66,67,70,88,89,90 fuelwood-90 fungi-46


gene pool-78general circulation model (GCM)-

27-33,36,38,66,67genetic base-71,76,77genetic variability-75,82,106genetic variation-66geologic history-4,6,31glaciers-4,5,7global warming potential (GWP)-

22,24global warming-1,18,60,92,112Global Environmental Facility-107grasslands-21,53grazing-22,53greenhouse eff ect-2,15,16,18,

23,25,33,38greenhouse gas (GHG)-15,16,18,

21-28,30growth-34,38,41,45-47,53,59,

74,80,86,90-93,107

habitat-64,75,96harvest scheduling-76harvesting-93-96,98hazard-67,71,76,78health-21,67,68,71,73,76,

77,83,113heat ¡stands-109Holdridge Life Zone-50,61homestead gardens-104hurricane-12,32,38,67hydrogen-10

ice age-1,5,7,10,11,16,2358

ice core-15,17,23,24increment-100,102Industrial Revolution-18,31infrastructure-105insects-46,57,68-71,76,77

79,90,106

integrated fire management-88integrated pestmanagement(IPM)-77

interglacial era-58interglacial period-16international agencies-84,106international agreements-83,84inventories-76,82

land use plan-104,112lightning-21,54,67lightning frequency-67lightning storms-54Little Ice Age-7,10,11livestock-53,54,87livestock management-21,87lumber-64

mangrove-64markets-64Medieval Optimum-7,8Mesozoic Era-4methane-18,19,24,37,46,53microbial activity-37,57microclimate-108migration-58,64Milankovitch Theory-10missing carbon sink-43mitigation-74,80,81,107,108models-28,30,53,63,66,83monitoring-23,77,78

Nnatural forest-49,96,103,112

113natural range-58,59,60,64,65

75,78nitrogen-18,37,70nitrogen fertilizers-19,43nitrogen fixation-37nitrogen oxides(NO)-18,21,37nitrous oxide(N20)-18,19,24non-wood products-98,101


G gene pool-78 general circulation model (GCM)-

27-33,36,38,66,67 genetic base-71 ,76,77 genetic variability-75,82,1 06 genetic variation-66 geologic history-4,6,31 glaciers-4,5,7 global warming potential (GWP)-

22,24 global warming-1, 18,60,92, 112 Global Environmental Facility-1 07 grasslands-21 ,53 grazing-22,53 . greenhouse effect-2, 15, 16, 18,

23,25,33,38 greenhouse gas (GHG)-15, 16, 18,

21-28,30 growth-34,38,41 ,45-47,53,59,

74,80,86,90-93, 107

H habitat-64,75,96 harvest scheduling-76 harvesting-93-96,98 hazard-67, 71,76,78 health-21 ,67,68,71,73,76,

77 ,83, 113 heat islands-1 09 Holdridge Life Zone-50,61 homestead gardens-104 hurricane-12,32,38,67 hydrogen-10

ice age-1,5,7,10,11,16,23 58

ice core-15, 17 ,23,24 increment-1 00, 1 02 Industrial Revolution-18,31 infrastructure-105 insects-46,57 ,68-71,76,77

79,90,106

integrated fire management-88 integrated pest management(lPM)-77

interglacial era-58 interglacial period-16 international agencies-S4, 1 06 international agreements-83,S4 inventories-76,82

L land use plan-1 04, 112 lightning-21 ,54,67 lightning frequency-67 lightning storms-54 Little Ice Age-7, 1 0, 11 livestock-53,54,87 livestock management-21 ,87 lumber-64

M mangrove-64 markets-64 MedievaIOptimum-7,S Mesozoic Era-4 methane-1S, 19,24,37 ,46,53 microbial activity-37,57 microclimate-10B migration-58,64 Milankovitch Theory-10 missing carbon sink-43 mitigation-74,80,81,1 07, 1 08 models-28,30,53,63,66,83 monitoring-23, 77,78

N natural forest-49,96, 1 03, 112

113 natural range-58,59,60,64,65

75,78 nitrogen-18,37,70 nitrogen ferti lizers-19,43 nitrogen fixation-37 nitrogen oxides(NO,)-18,21 ,37 nitrous oxide(N,O)-18 , 19,24 non-wood products-98,1 01


northern hemisphere-7,9,20,3343,58,75,110

nutrient-37,57,76

0ocean-5,9,11-13,20,27,30,31

32,34,40,41,43,93ocean circulation-9,34ocean currents-11,12offset-47,57,100,102,106organic matter-4,37,46,83,94ozone-18,21ozone hole-21

P

Palaeozoic Erapaper products-54,98peat-44peat bogs-44peat deposit-54peatlands-44,82pest management-77pests-36,64,67,68,71,72,76-78

96photosynthesis-27,34,35,45,57phytoplankton-9,12Pinatubo-11,20plant community-45,57,58,64plant health-71plantations-45,52,53,71,91-93

97,99-102,104-107,113plantation pests-71planting(s)-52,78,96,100-

112planting programme-77planting stock-76,77Pleistocene Period-7,58,64policies-74,80,85,94,113policy-3,85,112,113pollen-4,58,59pollen sterility-36,59precipitation-6,7,12,27,29,31

32,34-36,38,47,66,73,99

prescribed fire-54,88

prescription-54,76presuppression-77,88prevention-77,88provenance-76,77,100,104public utility companies-106

R

radiation-10,11,14,15,21,108rain forests-12,63,66,67rainfall-5,12,32,53,58,63,

67,68recycling-98ref orestation-77,100,102,104-

107,112,113regional climate change-73research-28,35,52,63,78,

81-83,86,104,105residence times-22roots-46rotation-99rotation age-98rotation length-76,99

S

silviculture-77sinks-2,12,30,40,42,43,45,49

74,80,82,96,99soil-4,19,21,27,32,36,37,40,41

46,47,49,51,56,57,6773,76,82,83,87,93,9498,99,102,104,108

soil nutrients,37,76solar radiation-10,11,15,31,110sources-2,18, 19,21,22,25,26,30

37,40,42,43,45,68,7480,82,85,86,88,90,9293,96,98,100,106,107113

southern hemisphere-7,9stems-45,46,94stress-66,67,68,70,73,75,76

84,106sun-9,10,11,14,15,26,110sunspots-10

, 26 Climate Change, Forests and Forest Management

northern hemisphere-7,9,20,33 43,58,75,110

nutrient-37 ,57 ,76

o ocean-5,9, 11-13,20,27,30,31

32,34,40,41,43,93 ocean circulation-9,34 ocean currents-' 1,12 ollset-47 ,57,100,1 02,106 organic matter-4,37,46,83,94 ozone-18,21 ozone hole-21

p Palaeozoic Era paper products-54,98 peat-44 peat bogs-44 peat deposit-54 peatlands-44,82 pest management-77 pests-36,64,67 ,68, 71,72,76-78

96 photosynthesis-27 ,34,35,45, 5 7 phytoplankton-9,12 Pinatubo-11,20 plant community-45 ,57,58,64 plant health-71 plantations-45,52,53, 71 ,9 1-93

97 ,99-102,104-107,113 plantation pests-71 plantingls)-52, 78,96,100-

112 planting programme-77 planting stock-76,77 Pleistocene Period-7,58 ,64 policies-74,80,85,94,113 policy-3,85, 112, 113 pollen-4,58,59 pollen sterility-36,59 precipitation-6, 7,12,27,29,31

32,34-36,38,47, 66,73,99

prescribed fire-54,88

prescription-54,76 presuppression-77 ,88 prevention-77 ,88 provenance-76,77, 100, 104

. public utility companies-106

R radiation-10, 11, 14, 15,21,108 rain forests-12,63,66,67 rainfall -5,12,32,53,58,63,

67,68 recycling-98 reforestation-77,1 00, 1 02, 1 04-

107,112,113 regional climate change-73 research-28 ,35, 52,63, 7 8,

81 -83,86,104,105 residence times-22 roots-46 rotation-99 rotation age-98 rotation length-76,99

S silviculture-77 sinks-2,12,30,40,42,43,45,49

74,80,82,96,99 soil-4, 19,21 ,27,32,36,37,40,41

46,47,49,51,56,57,67 73,76,82,83,87 ,93,94 98,99,102,104,108

soil nutrients,37, 76 solar radiation-10, 11,15,31 ,110 sources-2, 18, 19,21 ,22,25,26,30

37,40,42,43,45,68,74 80,82,85,86,88,90,92 93,96,98,100,106,107 113

southern hemisphere-7,9 stems-45,46,94 stress-66,67 ,68, 70, 73, 75, 76

84,106 sun-9, 1 0, 11,14,15,26,110 sunspots-10


Tambora-11temperateforest-46,50,53,64,71temperate ecosystem-60temperate region-56,110temperate zone-4,55,99,100

103,108temperature-1,5-7,9-17,22,27

28,30-39,47,53,58,59,61,62,64,68,71,109-111

terrestrial sink-43timber-96,112.timber harvesting-93-96timber salvage-78transpiration-9,53,63tree crowns-45tree improvement-76,78tree planting-71,104,105,107-

112tree ranges-58tree rings-4tree species-37,57-59,64,77,82

99,100,105tree(s)-8,46,57,65,94,109,110tropical deforestation-47,55

56tropical dry forest-49,50tropical ecosystem-60tropical forests-19,46,53,67,68

71,86,93,99,102Tropical Forests ActionProgramme (TFAP)-77,85,112

tropical moist forest-49,50tropical pines-68,69tropical rain forest-35,44,63,66

67tropical region-110tropical storms-31,32,33,64,67tropical wet forest-50tropical zone-99,108tundra-44,50,58typhoon-32

U

ultraviolet radiation-21UNCED-84UNDP-85,106,107UNEP-107urban foresters-109urban plantings-107urban trees-108-110utilization-92-94,112

Vvegetation-4,9,45,51,54,55

56,58,66,79,90,95,112vegetation communies-70vegetation type-61vegetation zone-62volcano-11,20,25volume(s)-19,25,41,47,67

70,88

warming-1-7,9,10,12,18,2224,26,32,33,58,6065,68,73,92,112

water-7,9,11,12,13,25,3435,39,40,56,57,6395,107,108

water resources-98,106water vapour-18watershed protection-112weather-4,5,9,11,12,21,32

44,88wildfire-36,47,54,66,67,70

76,78,88,90windbreak-45,103,104,108,110

111WMO-4wood-22,54,64,84,90,92,94

96-99,101,107,112113

wood energy-103wood processing-103wood products-54,71wood waste-93wooded area-45,46


T Tambora-ll temperateforest-46,50,53,64,71 temperate ecosystem-60 temperate region-56, 110 temperate lone-4,55,99,1 00

103,108 temperature-l ,5-7,9-17,22,27

28,30-39,4 7,53,58,59, 61,62,64,68,71,109-111

terrestrial sink-43 timber-96,112, timber harvesting-93-96 timber salvage-78 transpiration-9, 5 3,63 tree crowns-45 tree improvement-76,78 tree planting-71,104,105,107-

112 tree ranges-58 tree rings-4 tree species-37,,57-59,64,77,82

99,100,105 tree(sl-8,46,57 ,65,94,109,110 tropical deforestation-47, 55

56 tropical dry forest-49,50 tropical ecosystem-60 tropical forests-19,46,53,67,68

71 ,86,93,99,102 Tropical Forests Action Programme (TFAPI-77,85,112

tropical moist forest-49,50 tropical pines-68,69 tropical rain forest-35,44,63 ,66

67 tropical region-ll 0 tropicalstorms-3 1,32,33,64,67 tropical wet forest-50 tropical zone-99,1 08 tundra-44,50,58 typhoon-32

U ultraviolet radiation-21 UNCED-84 UNDP-85, 1 06, 1 07 UNEP-l07 urban foresters-l09 urban plantings-l07 urban trees-l 08-11 0 utilization-92-94,112

V vegetation-4,9,45,51 ,54,55

56,58,66,79,90,95,112 vegetation communies-70 vegetation type-6 1 vegetation zone-62 volcano-ll,20,25 volume(sl-19,25,41,47,67

70,88

W warming-1-7 ,9, 1 0 , 12, 18,22

24,26,32,33,58,60 65,68,73,92 ,112

water-7 ,9, 11,12,13,25,34 35,39,40,56,57,63 95,107,108

water resources-gB,1 06 . water vapour-18

watershed protection-112 weather-4,5,9, 11,12,21 ,32

44,88 wi ldfire-36,4 7 ,54,66,67,70

76,78,88,90 windbreak-45,1 03, 1 04, 1 08, 11 0

111 WMO-4 wood-22,54,64,84,90,92,94

96-99,101,107,112 113

wood energy-l03 wood processing-l03 wood products-54,71 wood waste-93 wooded area-45,46


wooded lands-54,103wooden structures-88woodlands-47,50,53,56,87,104woodland fires-88woodstoves-92woody material-66woody plants-45woody tissue-2,98woody vegetation-45World Bank-85,106,107

XYZyarding-94Year Without Summer-1 1


wooded lands-54,1 03 wooden structures-8B woodlands-47 ,50,53,56,87,104 woodland fires-88 woodstoves-92 woody material-66 woody plants-45 woody tissue-2,98 woody vegetation-45 World Bank-85 ,1 06, 1 07

XYZ yarding-94 Year Without Summer-' 1

FAO TECHNICAL PAPERS

FAO FORESTRY PAPERS

1 Forest utilization contracts on public land, 1977 (E F S)2 Planning forest roads and harvesting systems, 1977 (E F S)3 World list of forestry schools, 1977 (E/F/S)3 Rev.1 World list of forestry schools, 1981 (E/F/S)3 Rev.2 World list of forestry schools, 1986 (E/F/S)4/1 World pulp and paper demand, supply and trade 1- Vol. 1, 1977 (E F S)4/2 World pulp and paper demand, supply and trade - Vol. 2, 1977 (E F S)5 The marketing of tropical wood in South America, 1976 IE S)6 National parks planning, 1976 (E F S**)7 Forestry for local community development, 1978 (Ar E F S)8 Establishment techniques for forest plantations, 1978 (Ar C E* F S)9 Wood chips - production, handling, transport, 1976 (C E S)10/1 Assessment of logging costs from forest inventories in the tropics

1. Principles and methodology, 1978 (E F S)10/2 Assessment of logging costs from forest inventories in the tropics

2. Data collection and calculations, 1978 (E F S)11 Savanna afforestation in Africa, 1977 (E F)12 China: forestry support for agriculture, 1978 (E)13 Forest products prices 1960-1977, 1979 (E/F/S)14 Mountain forest roads and harvesting, 1979 (E)14 Rev.1 Logging and transport in steep terrain, 1985 (E)15 AGRIS forestry - world catalogue of information and documentation

services, 1979 (E/F/S)16 China: integrated wood processing industries, 1979 (E F SI17 Economic analysis of forestry projects, 1979 (E F S)17 Sup.1 Economic analysis of forestry projects: case studies, 1979 (E SI17 Sup.2 Economic analysis of forestry projects: readings, 1980 (C E)18 Forest products prices 1960-1978, 1980 (E/F/S)19/1 Pulping and paper-making properties of fast-growing plantation wood

species - Vol. 1, 1980 (E)19/2 Pulping and paper-making properties of fast-growing plantation wood

species - Vol. 2, 1980 (E)20 Forest tree improvement, 1985 (C E F SI20/2 A guide to forest seed handling, 1985 (E S21 Impact on soils of fast-growing species in lowland humid tropics, 1980

(E F S)22/1 Forest volume estimation and yield prediction

Vol. 1. Volume estimation, 1980 (C E F S)22/2 Forest volume estimation and yield prediction

Vol. 2. Yield prediction, 1980 (C E F SI23 Forest products prices 1961-1980, 1981 (E/F/S)24 Cable logging systems, 1981 (C E)25 Public forestry administrations in Latin America, 1981 (E)26 Forestry and rural development, 1981 (E F SI27 Manual of forest inventory, 1981 (E28 Small and medium sawmills in developing countries, 1981 (E SI

FAO TECHNICAL PAPERS

FAO FORESTRY PAPERS

1 2 3 3 Rev.1 3 Rev.2 4/ 1 4/2 5 6 7 8 9 10/1

10/2

11 12 13 14 14 Rev.1 15

16 17 17 Sup.l 17 Sup.2 18 19/ 1

19/2

20 20/2 21

22 /1

22/2

23 24 25 26 27 28

Forest utilization contracts on public land, 1977 (E F 5) Planning forest roads and harvesting systems, 1977 (E F S) World list of forestry schools, 1977 (E/F/S) World list of forestry schools, 1981 (E/F/S) World list of forestry schools, 1986 (E/F/S) World pulp and paper demand, supply and trade 1- Vol. " 1977 (E F 5) World pulp and paper demand, supply and trade - Vol. 2, 1977 (E F 5) The marketing of tropical wood in South America, 1976 (E SI National parks planning, 1976 (E F SU) Forestry for local community development, 1978 (Ar E F 5)

Establishment techniques for forest plantations, 1978 (Ar C E· F SI Wood chips - production, handling, transport, 1976 (C E S) Assessment of logging costs from forest inventories in the tropics - 1. Principles and methodology, 1978 (E F S) Assessment of logging costs from forest inventories in the tropics - 2. Data collection and ca lculations, 1978 (E F 5) Savanna afforestation in Africa , 1977 (E F)

China: forestry support for agriculture, 1978 (E) Forest products prices 1960-1977, 1979 (E /F/S) Mountain forest roads and harvesting, 1979 (E) Logging and transport in steep terrain, 1985 (El AGRIS forestry - world catalogue of information and documentation services, 1979 (E/F/S) China: integrated wood processing industries, 1979 (E F S) Economic analysis of forestry projects, 1979 (E F SI Economic analysis of forestry projects: case studies, 1979 (E SI Economic analysis of forestry projects: readings, 1980 (C El Forest products prices 1960-1978, 1980 (E /F/S) Pulping and paper-making properties of fast-growing plantation wood species - Vol. " 1980 (E)' Pulping and paper-making properties of fast-growing plantation wood species - Vol. 2, 1980 (E) Forest tree improvement, 1985 (C E F 5) A guide to forest seed handling, 1985 (E 5 ) Impact on soils of fast-growing species in lowland humid tropics , 1980 lE F SI Forest volume estimation and yield prediction - Vol. 1. Volume estimation, 1980 (C E F SI Forest vo lume estimation and yield prediction - Vol. 2. Yield prediction, 1980 (C E F SI Forest products prices 1961 -1980, 1981 (ElF/SI Cable logging systems, 1981 (C E) Public forestry administrations in Latin America, 1981 (El Forestry and rural development, 1981 lE F S) Manual of forest inventory, 1981 lE FI Small and medium sawmills in developing countries, 1981 (E SI

29 World forest products, demand and supply 1990 and 2000, 1982 (E F S)30 Tropical forest resources, 1982 (E F S)31 Appropriate technology in forestry, 1982 (E)32 Classification and definitions of forest products, 1982 (Ar/E/F/S)33 Logging of mountain forests, 1982 (E F S)34 Fruit-bearing forest trees, 1982 (E F SI35 Forestry in China, 1982 (C E)36 Basic technology in forest operations, 1982 (E F S)37 Conservation and development of tropical forest resources, 1982 (E F S)38 Forest products prices 1962-1981, 1982 (E/F/S)39 Frame saw manual, 1982 (E)40 Circular saw manual, 1983 (E)41 Simple technologies for charcoal making, 1983 (E F SI42 Fuelwood supplies in the developing countries, 1983 (Ar E F S)43 Forest revenue systems in developing countries, 1983 IE F S)44/1 Food and fruit-bearing forest species

1. Examples from eastern Africa, 1983 (E F S)44/2 Food and fruit-bearing forest species

2. Examples from southeastern Asia, 1984 (E F S)44/3 Food and fruit-bearing forest species

3. Examples from Latin America, 1986 (E SI45 Establishing pulp and paper mills, 1983 (E)46 Forest products prices 1963-1982, 1983 (E/F/S)47 Technical forestry education - design and implementation, 1984 (E F S)48 Land evaluation for forestry, 1984 IC E F SI49 Wood extraction with oxen and agricultural tractors, 1986 (E F50 Changes in shifting cultivation in Africa, 1984 (E F)50/1 Changes in shifting cultivation in Africa - seven case-studies, 1985 (E)51/1 Studies on the volume and yield of tropical forest stands - 1. Dry forest

formations, 1989 (E F)52/1 Cost estimating in sawmilling industries: guidelines, 1984 (E)52/2 Field manual on cost estimation in sawmilling industries, 1985 (El53 Intensive multiple-use forest management in Kerala, 1984 (E F SI54 Planificación del desarrollo forestal, 1984 (S)55 Intensive multiple-use forest management in the tropics, 1985 (E F56 Breeding poplars for disease resistance, 1985 (E)57 Coconut wood - Processing and use, 1985 (E SI58 Sawdoctoring manual, 1985 (E SI59 The ecological effects of eucalyptus, 1985 (C E F SI60 Monitoring and evaluation of participatory forestry projects, 1985 (E F S)61 Forest products prices 1965-1984, 1985 (E/F/S)62 World list of institutions engaged in forestry and forest products research,

1985 (E/F/S)63 Industrial charcoal making, 1985 (E)64 Tree growing by rural people, 1985 (Ar E F S)65 Forest legislation in selected African countries, 1986 (E F)66 Forestry extension organization, 1986 (C E S)67 Some medicinal forest plants of Africa and Latin America, 1986 (E)68 Appropriate forest industries, 1986 (E)69 Management of forest industries, 1986 lE)

29 World forest products, demand and supply 1990 and 2000. 1982 (E F 5) 30 Tropical forest resources, 1982 lE F S) 31 Appropriate technology in forestry, 1982 (E) 32 Classification and definitions of forest products. 1982 (Ar /E/F/S) 33 Logging of mountain forests, 1982 lE F S) 34 Fruit-bearing forest trees. 1982 (E F 5) 35 Forestry in China, 1982 (e El 36 Basic technology in forest operations. 1982 lE F SI 37 Conservation and development of tropical forest resources, 1982 (E F SI 38 Forest products prices 1962-1981. 1982 (E/F/S) 39 Frame saw manual, 1982 (E) 40 Circular saw manual, 1983 (E) 41 Simple technologies for charcoal making, 1983 lE F Sl 42 Fuelwood supplies in the developing countries, 1983 (Ar E F S) 43 Forest revenue systems in developing countries, 1983 lE F S) 44/1 Food and fruit-bearing forest species

- 1. Examples from eastern Africa, 1983 (E F S) 44/2 Food and fruit-bearing forest species

- 2. Examples from southeastern Asia, 1984 (E F S) 44/3 Food and fruit-bearing forest species

- 3. Examples from Latin America, 1986 (E S) 45 Establishing pulp and paper mills, 1983 (E) 46 Forest products prices 1963-1982, 1983 (E/F/S) 47 Technical forestry education - design and implementation, 1984 (E F 5) 48 Land evaluation for forestry, 1984 (C E F 51 49 Wood extraction with oxen and agricultural tractors . 1986 (E F SI 50 Changes in shifting cultivation in Africa, 1984 (E Fl . 50/1 Changes in shifting cultivation in Africa - seven case-studies, 1985 (E) 51/1 Studies on the volume and yield of tropical forest stands - 1. Dry forest

formations , 1989 (E F) 52/ 1 Cost estimating in sawmilling industries: guidelines, 1984 (E) 52/2 Field manual on cost estimation in sawmilting industries, 1985 (E) 53 Intensive multiple-use forest management in Kerala, 1984 (E F 5) 54 Planificaci6n del desarrotfo forestal, 1984 (5) 55 Intensive multiple-use forest management in the tropics, 1985 (E F SI 56 Breeding poplars for disease resistance, 1985 (El 57 Coconut wood - Processing and use, 1985 (E SI 58 Sawdoctoring manual, 1985 lE SI 59 The ecological eHects of eucalyptus, 1985 (C E F SI 60 Monitoring and evaluation of participatory forestry projects, 1985 lE F S) 61 Forest products prices 1965-1984. 1985 (E/F/S) 62 World list of institutions engaged in forestry and forest products research,

1985 (E/F/S) 63 Industrial charcoal making, 1985 (E) 64 Tree growing by rural people, 1985 (Ar E F SI 65 Forest legislation in selected Afri can countries. 1986 (E F) 66 Forestry extension organization, 1986 (C E S) 67 Some medicinal forest plants of Africa and Latin America. 1986 (E) 68 Appropriate forest industries. 1986 (E) 69 Management of forest industries, 1986 (E)

70 Wildland fire management terminology, 1986 (E/F/S)71 World compendium of forestry and forest products research institutions,

1986 (E/F/S)72 Wood gas as engine fuel, 1986 (E S)73 Forest products: world outlook projections 1985-2000, 1986 (E/F/S)74 Guidelines for forestry information processing, 1986 (E)75 Monitoring and evaluation of social forestry in India - an operational guide,

1986 (E)76 Wood preservation manual, 1986 (E)77 Databook on endangered tree and shrub species and provenances,

1986 (E)78 Appropriate wood harvesting in plantation forests, 1987 (E)79 Small-scale forest-based processing enterprises, 1987 (E F S)80 Forestry extension methods, 1987 (E)81 Guidelines for forest policy formulation, 1987 (C E)82 Forest products prices 1967-1986, 1988 (E/F/S)83 Trade in forest products: a study of the barriers faced by the developing

countries, 1988 (E)84 Forest products: World outlook projections - Product and country tables

1987-2000, 1988 (E/F/S)85 Forestry extension curricula, 1988 (E/F/S)86 Forestry policies in Europe, 1988 (E)87 Small-scale harvesting operations of wood and non-wood forest products

involving rural people, 1988 (E F S)88 Management of tropical moist forests in Africa, 1989 (E F P)89 Review of forest management systems of tropical Asia, 1989 (E)90 Forestry and food security, 1989 (Ar E SI91 Design manual on basic wood harvesting technology, 1989 (E F S)

(Published only as FAO Training Series, No. 18)92 Forestry policies in Europe - An analysis, 1989 (E)93 Energy conservation in the mechanical forest industries, 1990 (E SI94 Manual on sawmill operational maintenance,

1990 (E)95 Forest products prices 1969-1988, 1990 (E/F/S)96 Planning and managing forestry research: guidelines for managers,

1990 (E)97 Non-wood forest products: the way ahead, 1991 (E S)98 Timber plantations in the humid tropics of Africa, 1993 (E F)99 Cost control in forest harvesting and road construction, 1992 (E)100 Introduction to ergonomics in forestry in developing countries, 1992 (E F I)101 Management and conservation of closed forests in tropical America, 1993

IE F P 51102 Research management in forestry, 1992 (E F S)103 Mixed and pure forest plantations in the tropics and

subtropics, 1992 (E)104 Forest products prices 1971-1990, 1992 (E/F/S)105 Compendium of pulp and paper training and research institutions, 1992 (E)106 Economic assessment of forestry project impacts, 1992 (E F)107 Conservation of genetic resources in tropical forest management -

Principles and concepts, 1993 (E)

70 Wildland fire management terminology, 1986 (E/F/S) 71 World compendium of forestry and forest products research institutions,

1986 (E/F/S) 72 Wood gas as engine fuel, 1986 (E 5) 73 Forest products: world outlook projections 1985-2000, 1986 (E/F/S) 74 Guidelines for forestry information processing, 1986 (E) 75 Monitoring and evaluation of social forestry in India - an operational guide,

1986 (E) 76 Wood preservation manual, 1986 (E) 77 Databook on endangered tree and shrub species and provenances,

1986 (E) 78 Appropriate wood harvesting in plantation forests, 1987 (E) 79 Small-scale forest-based processing enterprises, 1987 (E F 5) 80 Forestry extension methods, 1987 (E) 81 Guidelines for forest policy formulation, 1987 (e E) 82 Forest products prices 1967-1986, 1988 (E/F/S) 83 Trade in forest products: a study of the barriers faced by the developing

countries, 1988 (E) 84 Forest products: World outlook projections - Product and country tables

1987-2000, 1988 (E/F/S) 85 Forestry extension curricula, 1988 (E/F/S) 86 Forestry policies in Europe, 1988 (E) 87 Small-scale harvesting operations of wood and non-wood forest products

involving rural people, 1988 (E F S) 88 Management of tropical moist forests in Africa, 1989 (E F P) 89 Review of forest management systems of tropical Asia, 1989 (E) 90 Forestry and food security, 1989 (Ar E 5) 91 Design manual on basic wood harvesting technology, 1989 (E F 5)

(Published only as FAO Training Series, No. 18) 92 Forestry policies in Europe - An analysis, 1989 (E) 93 Energy conservation in the mechanical forest industries, 1990 (E 5) 94 Manual on sawmill operational maintenance,

1990 (E) 95 Forest products prices 1969-1988, 1990 (E/F/S) 96 Planning and managing forestry research: guidelines for managers,

1990 (E) 97 Non-wood forest products: the way ahead, 1991 (E 5) 98 Timber plantations in the humid tropics of Africa, 1993 lE F) 99 Cost control in forest harvesting and road construction, 1992 (E) 100 Introduction to ergonomics in forestry in developing countries, 1992 (E F I) 101 Management and conservation of closed forests in tropical America, 1993

(E F P 5) 102 Research management in forestry, 1992 (E F 5) 103 Mixed and pure forest plantations in the tropics and

subtropics, 1992 (E) 104 Forest products prices 1971 -1990, 1992 (E/F/S) 105 Compendium of pulp and paper training and research institutions, 1992 (E) 106 Economic assessment of forestry project impacts, 1992 (E F) 107 Conservation of genetic resources in tropical forest management -

Principles and concepts, 1993 (E)

108 A decade of wood energy activities within the Nairobi Programme ofAction, 1993 (E)

109 Directory of forestry research organizations, 1993 (E)110 Proceedings of the Meeting of Experts on Forestry Research, 1993 (E/F/S)111 Forestry policies in the Near East region - Analysis and synthesis, 1993

(E)

112 Forest resources assessment 1990 - Tropical countries, 1993 (E)113 Ex situ storage of seeds, pollen and in vitro cultures of perennial woody

plant species, 1993 (E)114 Assessing forestry project impacts: issues and strategies, 1993 (E F S)1 15 Forestry policies of selected countries in Asia and the Pacific, 1993 (E)116 Les panneaux à base de bois, 1993 (F)117 Mangrove forest management guidelines, 1994 (E)118 Biotechnology in forest tree improvement, 1994 (E)119 Les produits bois reconstitués, liants et environnement, 1994 (F)120 Decline and dieback of trees and forests - A global overview, 1994 (E)121 Ecología y enseñanza rural - Manual para profesores rurales del área

andina, 1994 (S)122 Readings in sustainable forest management, 1994 (El123 Forestry education - New trends and prospects, 1994 (E F)124 Forest resources assessment 1990 - Global synthesis, 1995 (E)125 Forest products prices 1973-1992, 1995 (E/F/S)126 Climate change, forest and forest management - an overview, 1995 (E)

Availability: March 1995

Ar - Arabic Multil MultilingualChinese Out of print

E English In preparationItalianFrench

- PortugueseSpanish

The FAO Technical Papers are available through the authorized FAO Sales Agents ordirectly from Distribution and Sales Section, FAO, Viale delle Terme di Caracalla, 00100Rome, Italy.

3

108 A decade of wood energy activities within the Nairobi Programme of Action, 1993 IEI

109 Directory of forestry research organizations, 1993 (E) 110 Proceedings of the Meeting of Experts on Forestry Research. 1993 (E/F/S) 1 1 1 Forestry policies in the Near East region - Ana lysis and synthesis, 1993

IEI 1 12 Forest resources assessment 1990 - Tr,opical countries. 1993 (E) 113 Ex situ storage of seeds, pollen and in vitro cultures of perennial woody

plant species, 1993 (E) 114 Assessing forestry project impacts: issues and strategies. 1993 (E F S)

115 Forestry policies of selected countries in Asia and the Pacific, 1993 (E) 116 Les panneaux ill base de bois, 1993 (F) 117 Mangrove forest management guidelines, 1994 (E) 118 Biotechnology in forest tr~e improvement, 1994 (E) 119 Les produits bois reconstitu~s, liants et environnement, 1994 IF) 120 Decline and dieback of trees and forests - A global overview. 1994 (E) 121 Ecologfa y enseiianza rural - Manual para profesores rurales del area

andina. 1994 (S)

122 Readings in sustainable forest management, 1994 (E) 123 Forestry education - New trends and prospects, 1994 lE F) 124 Forest resources assessment 1990 - Global symhesis, 1995 (E) 125 Forest products prices 1973-1992, 1995 (E/F/SI 126 Climate change, forest and forest management - an overview, 1995 (E)

Availability: March 1995

A, -C

E

Arabic Chinese English

- Italian F - French P - Portuguese S - Spanish

Multil - Multilingual Out of print In preparation

The FAO Technical Papers are avaIlable through the authorized FAO Sales Agents or directly from Distribution and Sales Section, FAO, Viale delle Terme di Caracalla, 00100 Rome, Italy.

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