Environmental Engineering Reference
In-Depth Information
forests and shrublands following land abandonment also has hydrological conse-
quences, which are related to increased evapotranspiration and a reduction of run-
off (Puigdefabregas and Mendizabal, 1998). Conversely, a reduction in vegetation
cover through land use intensification results in the reduction of evapotranspiration
while run-off is increased thus increasing the risk of flooding and damage to engi-
neering structures due to soil erosion and sedimentation (Mulligan
et al.,
2004). Fi-
nally, the build-up of vegetation biomass after land abandonment increases the risk
of severe wildfires, which can also lead to soil erosion. In Spain, the area burned
annually increased significantly between 1960 and 1990, generating a debate about
the relation between wildfires and vegetation cover (Puigdefabregas and Mendiza-
bal, 1998).
8.6 Conclusion
Although there are cases of massive deforestation in antiquity (e.g. the cypress
forests of Crete, cedar forests of Mount Lebanon), substantial land use changes in
the Mediterranean mountains started much later, in the medieval period, when wars,
famines and malaria in the lowlands forced people to move to the uplands. These
changes were intensified in the eighteenth and nineteenth centuries when popula-
tions increased and the Industrial Revolution greatly improved transport between
lowlands. The beginning of the twentieth century, however, marked the start of ru-
ral emigration from the mountains of northern Mediterranean countries that peaked
after the Second World War, resulting in land abandonment and the remarkable in-
crease of forest cover seen in recent years. In southern Mediterranean countries, in
contrast, an opposite trend is recorded due to the substantial increase in the rural
population and consequent pressure on the mountains for arable and grazing land.
Recent land use changes have disrupted the traditional agro-silvo-pastoral equilib-
rium of the Mediterranean mountains. The increased forest cover in the northern
Mediterranean has resulted in a decline in species and especially of habitat diver-
sity and an increase in natural hazards, especially wildfires, but increased carbon se-
questration and decreased soil erosion and sediment transport to the lowlands. The
decrease of forest cover in the southern Mediterranean, on the other hand, has led
to severe soil erosion. A long-term monitoring system of all these land use changes
should be established and new equilibriums should be pursued in the Mediterranean
mountains so that their environment is conserved and the prosperity of mountain
people is better served.
8.7 Acknowledgements
Appreciation is expressed to the editor for his constructive comments.
