Interaction of climate change and land degradation: the experience in the Arab region.

• Author: El-Bagouri, Ismail H.M.

The Arab region is comprised of 21 countries, extending from North Africa to South West Asia, over an estimated total area of 14.1 million square kilometres. Its vast terrain includes physiographic features of plains, plateaus, dry valleys and relatively limited highlands and mountainous areas.

Countries of the region are distinguished by vast coastal areas overlooking segments of the Arabian Gulf, the Arabian sea, the Red Sea, the Mediterranean Sea and the Atlantic Ocean. The region's population is expected to reach over 290 million by 2010, with a continued growth rate estimated at an average of 2 per cent per annum.

Aridity is the main climatic feature of the Arab region, and hyper-arid or arid conditions prevail in over 89 per cent of the area, while the remaining 11 per cent of semiarid and limited sub-humid areas are confined to elevated lands. Marginal rainfall of up to 350 millimetres per year extends over the arid areas, while semi-arid zones experience between 400 and 800 mm/year and sub-humid areas between 800 and 1,500 mm/year. However, rainfall throughout the region is characterized by rapid changes in spacial distribution, seasonal variation, inter-annual variability, varied intensities of sporadic showers and changing lengths of the growing season. Most Arab countries experience highly variable rainfalls and recurrent drought spells of varied severity and length. Such high variabilities extend to average annual temperatures, as well as maximum and minimum temperatures, varying from freezing to a high of over 50° Celsius, depending on the season and location.

These data clearly demonstrate the significant impact of climatic features on land-use categories and the productivity of each category, with special reference to rangelands, rain-fed cultivated areas and the degradation processes in the region. Among the most influential climatic factors is rainfall. The total amount of rainwater received in the Arab region is estimated at 2282 billion [m.sup.3]/year, compared to an estimated 205 billion [m.sup.3]/year for surface water and 35 billion [m.sup.3]/year for groundwater. This clearly shows that the mostly marginal rainfall in the region represents the major water resource available, despite the constraints facing water efficiency. As a result, national country reports clearly show that a major fraction of the rainwater received is lost through the combination of evapotranspiration, seepage, run-off and flash floods through...