In the arid zone of the Middle East, dynamic relations between precipitation, runoff, soil development and soil erosion are inducing water availability and natural biomass. These dynamic relations are dictated by the glacial – inter glacial oscillations, supper-imposed on a general trend of permanent aridity observed during the last 2 Ma. Present manifestations of this process is the widespread phenomenon of naturally induced soil erosion, initiated 20,000 years BP at the transition from the last glacial phase to the present interglacial phase and intensified during the Holocene.
The aggressive process of soil erosion gradually
removes the loessic soils that developed during the last glacial event, holding
agriculture potential. Simultaneously, as the bedrock exposed, this process
contributes to runoff generation and water availability. As this process is
self-accelerated, the rate of soil erosion is gradually increasing.
Pastoral and agricultural societies living on
these lands throughout the Holocene has intensified or slowed down the natural
process of soil erosion. Intensified grazing can cause accelerated soil erosion
and desertification while construction of agriculture installations such as
terraces can contribute to soil conservation. In this regard, the remains of
the farming society that lived in the Negev Highland of Southern Israel during
the Byzantine and Early Muslim eras (1700-1100 BP) are giving insights on
large-scale and long-term actions of soil protection. During this period, most
of the valleys were terraced and leveled, aiming to protect agriculture soils
and to slow-down the flood energy, permitting flood water to percolate into the
soil. Hundreds of cisterns were dug, offering drinking water for humans and
herds. The crops in the agricultural plots were mainly cereals – barley and
wheat, while orchards of olive and grapes were planted in deep irrigated soils.
Plantation of similar orchards at present, solely irrigated by runoff, prove
that the ancient agricultural enterprises were constructed under similar arid
climate, limited to 130-70 mm/y. All environmental indicators in the region
hints on the stability of the present climate for the last 3000 years.
At present, agriculture potential is still kept
in the majority of this arid zone. However, positive feedback mechanism is
speeding-up soil erosion, promoting desertification. As a globe-wide warning
was set for combating desertification, the effect of increased water
availability combined with new agriculture techniques, reinforced by solar
energy, are giving hope for better land management that will slow down the
natural desertification process in arid zones glob-wide.