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• Dryland environment • Desertification • Livestock grazing in drylands • Agriculture in drylands

• Sustainability of dryland agriculture

Agroecology Ecological understanding of farming systems

Ben-Gurion University of the Negev

8. Sustainable dryland agriculture

bboeken@bgu.ac.ilhttp://www.bgu.ac.il/desert_agriculture/Agroecology/© BBoeken 2005-17

2 http://www.landroverclub.net

The dryland environment •  Temperature

-  Hot, warm and cold deserts -  Usually high in summer

•  Rainfall –  Low rainfall (<400 mm/yr) –  High variability –  Periodic drought –  Unpredictability –  Seasonality

Ten year average annual rainfall for the Yuma Valley, AZ, USA (AZMET, Yuma Ag Center).

http://cals.arizona.edu

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The dryland environment •  Soils

–  Weathering and dust –  Salinity –  Biological soil crusts –  Erosion

observe.arc.nasa.gov

Bare soil (Negev)

Salt flat; staffwww.fullcoll.edu

Cyanobacterial soil crust (Negev)

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The dryland environment •  Vegetation

–  Spatial heterogeneity •  Patchiness •  Contraction along stream-beds

Sonoran Desert; www.dees.dri.edu

–  Growth forms •  Herbaceous plants

-  Winter annuals, geophytes and hemicryptophytes

•  Woody plants -  Shrubs, dwarf-shrubs and trees -  Drought tolerant or deciduous

Northern Negev shrubland

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Desertification

•  Approaches –  Expanding deserts (?) –  Local degradation

•  Runoff and erosion •  Sand movement •  Scale, off-site effects

Causes – Climatic (droughts) – Human impacts

•  Overgrazing •  Inappropriate cultivation •  Clearing, deforestation •  Water over-use •  Soil degradation

Of natural and cultivated landscapes

http://www.idrc.ca/en/ev-92240-201-1-DO_TOPIC.html http://www.abc.net.au/science/photos/desertification/photo7.htm

http://www.geog.leeds.ac.uk/people/m.kirkby/DIS4ME_1104/introduction.htm

Livestock grazing in drylands Morethan2billionpeopleliveinwater-limitedsystems

• Maineconomicac7vi7esarelivestockgrazingandsmall-scaledryfarming

• Age-oldtradi7ons,knowledgeandvalues• Unpredictablerainfallandprimaryproduc7on

Remote,peripheralcommuni7esindevelopingcountries

•  Increasingpopula7ondensity•  Poli7callyunder-represented,underprivileged

•  Poorlydocumentedordisputedownership

•  Displacementbywar,famineandirriga7on-basedagriculture 6

Grazing in semi-arid ecosystems

Whatistheroleoflivestockgrazinginlanddegrada7on(deser7fica7on) ofsemi-aridshrubland?

•  Arethereposi7veeffects,oronlynega7veones?

•  Aretheseeffectsreversible?

DoesgrazingcauseashiJfroma

func7onaltoadegradedstate?• Whatarethesestates?

•  Howdoesgrazingaffectthem?

• Whataretheconsequences?

Prim

ary

prod

uctio

n

Grazing intensity

collapse

recovery Degradedstate

Func.onalstate

Catastrophetheory

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Grazing and degradation High livestock stocking rates

(and clear-cutting and plowing) in combination with drought

can lead to transition of shrubland to crusted or bare soil,

with multiple consequences:

!  Resourceloss!  Soilerosion

!  Flash-floods!  Inunda7on

!  Reducedproduc7vityand!  Biodiversity

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Grazing experiment

Grazingplots!  10plotsof2mx4montwoslopes

!  Grazingexclosuressince1992in5plots!  Grazingby50sheepx4days/spring

(“moderategrazingpressure“)

ExclosureofgrazingbyBedouinsheepherdsinParkShakedLTER

5fencedplots5grazedplots

Datacollec7on

!  Shrubpatchsizes1993,2007,2010

!  Herbaceousdensityanddiversity

1993-2010

!  In6samples(20x30cm)

perplot

!  3inshruband3incrustedpatches

!  Sampledbeforegrazing 9

Long-term grazing impacts

Shrubpresenceandcanopysizein1993and2007

! Over15years,therewashighmortality(aJerthedrought),especiallyingrazedplots.

! Withoutgrazingthesmallershrubsdied;ingrazedplotstheywereallsmaller.

! Inallplotstherewerenew,smallshrubs;withgrazingfewerthanwithoutgrazing.

SurvivedDied New1993 2007

0

4

8

12

16

No.ofshrub

s

Prop

.can

opyarea

0.00

0.05

0.10

0.15

0.20

Survived Died Survived New1993 2007

Notgrazed

Grazed

GrazingF[1,315]=3.8081,p=0.0519GroupF[3,315]=0.3440,p<0.0001Grazing*GroupF[3,315]=0.1189,p=0.0162

onthedwarfshrubsNoaeamucronataandAtractylisserratuloidesin5grazedand5non-grazedplotsof2mx4m,1993-2007

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Agriculture in drylands •  Ancient runoff farming

–  Channels on slopes to divert runoff water –  Fields on terraces in wadis –  Diversion dams in large wadis

•  Modern runoff farming –  Within-watershed runoff use

•  Local retention •  Diverted

–  Off-site use •  Limanim •  Terraces

Nabattean terraces, Nitzana, Western Negev

Liman, Central Negev

Runoff catchment, Central Negev

Contour dikes (shikhim) Northern Negev

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Agriculture in drylands •  Irrigated farming

–  Water import –  Flooding, dripping

Drip irrigation, Arava

Irrigation canal, California

Greenhouses, Arava

•  High-tech agriculture –  Greenhouses –  Cooling –  Hydro/aeroponics –  Bio-control

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Alternative dryland land-use •  Integrated agriculture

–  Runoff agro-forestry

–  Agro-silvi-pastoralism

–  Rangeland pastoralism

–  Animal husbandry

–  Alternative agricultural practice

and life-style •  Sustainable dryland activities

–  Eco- and agro-tourism –  Adaptive building –  Home industry –  Desert gardening and nurseries –  Information industry –  Environmental education –  Health care –  Environmental art –  Spiritual retreats