Environmental Engineering Reference
In-Depth Information
CONCLUSION
The present ecosystems of Mediterranean regions can be regarded as the degraded
remnants of a biome which was once dominated by mixed evergreen and deciduous
forest. The two reasons for this situation are climate and anthropogenic influence.
Mediterranean regions were cool and dry in glacial times (
c
. 15,000 years BP), treeless
steppe being characteristic. Temperatures ameliorated in the Holocene to reach a
maximum some 5000 years BP. A continuous forest cover of evergreen and deciduous
trees had established itself by then.
The Mediterranean landscape is like a palimpsest; it shows the remains of successive
human societies superimposed on the landscape and on one another. Those societies, in
the Mediterranean region itself, have had successive impacts on the natural landscape
from Neolithic settlement, Bronze Age people, Phoenicians, Greeks, Romans and Moors.
Modern pressures have continued, with agricultural intensification, irrigation and all the
trappings of tourism. Tourist villages and golf courses now exist side by side with
irrigated citrus plantations and horticulture under polythene sheeting. Increasingly the
natural vegetation and soils are restricted, just as in Britain, to inaccessible 'islands' and
unwanted rocky hillsides.
KEY POINTS
1
Mediterranean ecosystems are dominated by the seasonality of the Mediterranean
climate. Plants and animals have devised many strategies to adapt to, and survive in,
the hot, dry summer. Production and reproduction take place during the more humid
and cooler period from autumn to spring. This is the time when most weathering,
geomorphological processes and soil-forming processes are operative too.
2
Despite the overriding importance of climate, there are variations in vegetation and soil
according to regional and local factors. A zonation of ecosystems is found with
increasing altitude. There is also a very powerful effect of aspect due to different
annual radiation budgets on north- and south-facing slopes. There is also a change in
vegetation from valley side to valley floor, related to moisture availability.
3
The final set of controls on Mediterranean ecosystems is the many human pressures -
hunting, grazing, deforestation, fire and cultivation. The net result of these pressures
over millennia has been to reduce the extent of the natural Mediterranean evergreen
forest. Many of the shrubby and steppe-like vegetation communities we see today
have been degraded from the forest, but equally some are themselves natural under the
stressful environmental conditions. Soil erosion has been accelerated, making the
depth of soil another key factor influencing vegetation. There are often big contrasts
between the rocky outcrops and thin soils of ridges and upper slopes and the deeper
soils of valleys and depressions.
