ASSESSMENT OF SOIL DEGRADATION IN THE CANARY-ISLANDS (SPAIN)

In the Canary Islands a number of factors, both natural and induced by human activity, act on the fragile ecosystems and agricultural land t o cause increasing problems with desertification and progressive degra dation of soil productivity. The results of an assessment of soil degr adation in the Canary Islands, the processes, causes and impacts, are presented in this paper. Although several processes and factors contri bute to soil degradation in the Canary Islands, two have been found to exert a greater qualitative influence: (a) accelerated erosion (water and aeolian); (b) salinization-sodification (natural and induced by a gricultural use). Approximately 40 per cent of the Canary Islands' lan d is undergoing rapid erosion. The factors involved may be grouped int o: natural erosion-torrential rainfall, sparse vegetation, high soil e rodibility, rugged relief; and erosion due to human activities-unsuita ble management of arable soils on the steep slopes, overgrazing and de forestation. About 60 per cent of the surface of the archipelago, incl uding areas given over to intensive agriculture, is affected by salini zation. The main factors responsible are: natural-an arid climate and a regime of oceanic winds; and human activities-overexploitation of th e aquifers, irrigation with water having a high salt and/or sodium con tent, intensive monoculture, and excessive and indiscriminate use of c hemical fertilizers and other agrochemicals.