Vegetation degradation and

land use changes in

agrosilvopastoral systems

Vasilios P. Papanastasis Aristotle University of Thessaloniki, Greece

Agrosilvopastoral systems

complex systems

crops, trees and pasture / animals

silvopastoral and silvoarable

combination of components

in the same unit of land

in a spatial sequence

Vegetation of agrosilvopastoral systems

rich and variable

trees, shrubs, herbaceous species

spontaneous, cultivated

complex energy and nutrient webs

vulnerable to human practices

affected by

land use changes

socio-economic conditions

Historical development

of agrosilvopastoral systems

traditional systems

savanna-like landscapes

crop mixtures

olive tree in the first millennium BC

dehesas in the Middle Ages

common land use

Classification of agrosilvopastoral systems

1. Overstory trees

spontaneous vs planted

evergreen vs deciduous

2. Understory crops

cereals vs forage crops

3. Grazing animals

sheep, goats, cattle, pigs

Spontaneous evergreen species

Quercus rotundifolia Quercus suber

Quercus coccifera Pinus halepensis

Spontaneous deciduous species

Quercus ithaburensis

Quercus frainetto

Pyrus amygdaliformis

Mixed systems

Planted trees (evergreen & deciduous)

Mixed systems

Ceratonia siliqua

Juglans regia

Olea europaea

Degradation processes

Extensification or abandonment

Reduction of labor

Rural emigration

Uplands (mainly)

Intensification

Mechanization

Increase of inputs

Lowlands (mainly)

Figure 1. Degradation of agrosilvopastoral systems through extensification of management activities

Wooded grasslands Silvopastoral systems

Wooded shrublands

Woodlands

Agrosilvopastoral systems

Vegetation and land degradation

Vegetation and land degradation

Tree clearing +

Land consolidation +

Mechanized agriculture +

Industrial crops

Over-pruning of trees +

Seeding of pasture species +

Improved animal breeds +

Increased shocking rates

Introduction of new species +

Employment of dense spacing +

Creation of plantation forests +

Mechanical exploitation

Agrosilvopastoral systems

Figure 2. Degradation of agrosilvopastoral systems through intensification of management activities

Figure 3. Degradation of montados in south Portugal (after Pinto-Carreia and Mascarenhas, 1999)

Montados

Vegetation and land degradation

Infrequent shrub clearing

Poor tree health

Shrub encroachment

Over-pruning of trees +

Too frequent cork collection +

Careless mechanical clearing +

Over-cropping +

Over-stocking

Case study of south Portugal

Over-grazing

Shrub encroachment

Over-pruning

Frequent cork collection

Dehesas - Montados

Case study of central Greece

(Portaikos-Pertouli valley)

Area: 12.5 Km2

Altitude: 200-2060 m a.s.l

Population: 4,928 people

Portaikos Pertouli valley

General view Mixed systems

Upper part of the valley Lower part of the valley

Table 1. Land cover/use changes between 1945 & 1992 in Portaikos and Pertouli valley

Category Area Change (%)

1945 1992

Artificial surfaces 84 147 + 75.00

Arable lands 1877 1000 - 46.72

Grasslands 1589 1084 - 31.78

Shrublands 975 872 + 10.56

Very open (

Total population changes

0

1000

2000

3000

4000

5000

Upper zone Lower zone Total

Elevation Zone

Popu

lation

1961 1971 1981 1991

Livestock number changes

0

4000

8000

12000

16000

20000

Upper zone Lower zone Total

Elevation zone

Anm

als

1961 1971 1991

Case study of Western Crete (White Mountains)

Area: 424 Km2

Altitude: 0-1,800 m a.s.l

Population: 6,000 people

Table 2. Changes of Mediterranean ecosystems in the study area of western

Crete between 1945 & 1989

Type of ecosystem Area Change (%)

1945 1989

Phrygana 7,934 6,544 - 17.5

Carriques 6,020 4,832 - 19.7

Maquis 4,222 3,668 - 13.1

Coniferous forests 10,504 12,632 + 20.3

Very open ( 70%) 4,648 8,136 + 75.0

Total 28,680 27,676 - 3.5

Total population changes

Livestock number changes

End result: wildfires

1992

1995

Case study of central Crete

(Psilorites Mountain)

Area: 500 Km2

Altitude: 600-2,456 m a.s.l

Population: 8,000 people

Cessation of cropping Restriction of trees

Over-grazing Degradation

Psilorites mountain

Land cover changes in Psilorites

between 1961 & 1989

Ha

0

10000

20000

30000

40000

Artificial

surface

Arable lands Forests Shrublands Grasslands Bare rock

1961 1989

Evolution of

land cover / use

between

1961 and 1989

1961

1989

Human population

Sheep Goats

1961

1971

1991

Conclusions There is a great variety of agrosilvopastoral systems all over

the Mediterranean

Eastern Mediterranean has less extensive and organized

systems compared to dehesas and montados of the western

Mediterranean but a great variety of poorly identified and

less studied systems

Vegetation of agrosilvopastoral systems, especially trees, are

very vulnerable to land use changes

Both extensification and intensification of human activities

result in vegetation and land degradation

Recommendations

Agrosilvopastoral systems have a great biological, scenic and

historical value and should be preserved as cultural landscapes

A joint study should be taken across Mediterranean to

identify and study the less widespread and known

agrosilvopastoral systems before their extinction

Agrosilvopastoral systems should be included in the agro-

environmental measures so that financial incentives are

provided to their owners for their conservation