Fjölrit RALA - 05.12.1999, Blaðsíða 33

NlCHOLAS J. YASSOGLOU ET AL.
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• There is need for intemational networks for research, monitoring, early
waming and mitigation.
• Intemational, regional and local cooperation for bottom-up mitigation practice
is need. The active participation of the people affected is necessary.
Thelesvos casr
An example of desertification in the Mediterranean Europe could be the land degrada-
tion in the Greek island of Lesvos. The island is located at the eastern border of
Europe, across Asia Minor. Its total area is about 161.000 hectares and it has been un-
der effective human influence for about 3500 years.
Three distinct climatic zones: semi-arid, transitional and subhumid exist in the is-
land. Desertification is widespread in the semi-arid zone, located in the west part of
the island, and fragmented in the transitional zone located in central part of the island
(Kosmas et al. 1996).
The dominant process of soil degradation is erosion following the thinning of the
vegetative cover by human action. The sequence of events directly or indirectly re-
lated to human action and lead to the desertification of the land, in the semi-arid and
transitional zones, are as follows:
• Destmction of the forest around 4000 years BP.
• Soil degradation due to soil erosion in the cultivated and grazed sloping land.
• Severe drop of land’s productivity leading to abandonment of agriculture
(around 500 to 40 years BP).
• Grazing of the abandoned lands further degrades the land.
• Occupation of pasture by non palatable plants mainly phiy'gane dominated by
thomv Sarcopoterium spinosum L. arrest soil erosion, but contribute to eco-
nomical desertification.
• Sharp increase of overgrazing accompanied by periodic buming of soil pro-
tecting Sarcopoterium spinosum (since 1955 AD).
• Very severe erosion and irreversible desertification (present).
Grazing animals act upon the soil accelerating erosion in a multiple ways, such as:
• Thinning of the vegetative cover.
• Compacting the soil surface, thus, reducing infiltration and increasing run-off.
• Digging the wet, soft soil and creating micro-escarpments, which create water
microturbulance and enhance the erosive power of the surface mn-off.
• Translocating downslope the protective stony mulch on the soil surface, thus
reducing its resistance to erosion and the retainable soil moisture.
The sequence of land degradation steps are summarized in Figure 3.