Coastal Irrigated Agriculture.

It includes the provinces from the Iberian South-East (Alicante , Murcia and Almeria ) and the Eastern Canary Islands (Las Palmas ). The most menaced of them are Murcia and Almeria, while Alicante and Las Palmas show a smaller increase of indicator values concerned with the concentration of economic activity and rural population. Two drivers of land degradation have been identified. The first is the sustainability loss of the intensive horticulture by over-explotation of water resources. The second concerns the expansion of almond tree crops over marginal areas in the Iberian South-East.

Sustainability loss of intensive agriculture.

This situation arises from the market effect on a demand increase of agricultural products above the available resources, and a low cost of water, which is evaluated as a 5% of the total inputs (Muñoz Martínez 1991). Water supply and water quality are likely to provide the only feedbacks to limit the increase of irrigation in the area.

Over-exploitation of aquifers reaches negative balances of around 400 hm3 year-1 (Direccion General de Obras Hidraulicas, Ministerio de Medio Ambiente 1998). External water inputs, as transfer from other basins and desalinisation, are being developed. There are drawbacks for both options. The first triggers inter-regional confrontations in long drought periods, while the latter leads to a dangerous dependency on the energy prices.

The quality of water resources is downgraded by marine salt intrusion and by pollution with agrochemicals. The former affects the 80% of aquifers in the area (Direccion General de Obras Hidaulicas 1994) although its evolution is difficult to predict because of connectivity differences between aquifers and the sea (Pulido et al 1993). The latter reaches extreme conditions, for example, more than 100 mg l-1 in the ground water of some areas (Direccion General de Obras Hidraulicas 1994).

Some structural factors of the involved land use systems impair also these agricultural systems. One of them is sand supply, which is required by greenhouse agriculture, in Almeria, at a rate of 1 hm3 y-1 (Muñoz 1995). The scarcity of sand sources leads to the exploitation of fossil dunes and apical areas of alluvial fans, causing important environmental problems. Almeria greenhouses produce around 1 Million Tm of fresh crop residues each year, and its recycling is still an unsolved problem. Incineration is expensive because it involves the removal of very large volumes. Using residues to feed livestock has the advantage of producing manure, an important input to greenhouses, but eliminating agrochemicals and plastic strings are expensive operations.

Expansion of almond tree crops over marginal areas.

Almond tree crops have increased x3 from 1965 to 1995 as a result of agricultural policies at national and European levels. They expand over hilly marginal areas with high slope angles. Field results show that sheet wash, rill erosion and tillage erosion lead to very important soil losses in these areas (50%-60% of bare ground rates) (Moreira 1991, Poesen et al. 1999).