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