Southern Continental Irrigated Agriculture.

Desertification risk affects the provinces of Albacete and Ciudad Real . Both are included in ‘La Mancha’ region, in the East-southern sector of the Iberian inner plateau.

Traditional agriculture of the area combined olive orchards, wine and graincrops. During the last 40 years, this system evolved to irrigated forage crops (alfalfa and maize) associated with sheep breeding, together with industrial crops (sunflower) and upgraded wine crops, most of them under irrigation using ground water The irrigated area increased by a factor of six during the reference period, while sunflower expanded x50 during the same period. These changes occurred at expense of olive orchards and cereals which have lost 37 000 ha and 107 000 ha respectively.

Such transformations were driven by big investments in irrigation developments, combined with stimuli from agricultural policies. However, temperature restrictions limit irrigation systems to relatively low demand products, such as forage and livestock. By this reason, the achieved gains in terms of agricultural value added and limitation of demographic drainage have been only moderated. The agricultural sector did not attain the necessary dynamism to control the unemployment, which attains a 30% of active population in Albacete.

The main factors that put in danger the sustainability of ‘La Mancha’ agricultural systems are over-exploitation of aquifers and wetland degradation. Both of them are inter-related and can be considered as symptoms of current desertification. A third factor into account is sunflower expansion. It is often rotated with grain crops, and it is often regarded as an ‘ecological crop’ because it covers the ground in summer and protects the soil from erosion. However, summer droughts often limit this protection effect. Available estimates of soil erosion in cereal-sunflower rotations point at rates as high as 60%-75% of bare ground values (Moreira 1991). 

Over-exploitation of aquifers is particularly dramatic in Ciudad Real, with a negative balance of 240 m3 y-1 (Direccion General de Obras Hidraulicas 1994) which amounts to a 2% of the available water reserves. This not only shortens the life span of the resource, but also increases its recover time to more than one century, even if extractions were stopped.

Such deficits in ‘La Mancha’ ground water systems mean that the water tables are descending at rates of around 1 m y-1 (Romero et al 1997). This feature leads to off site effects with relevant environmental consequences. One of them is the reduction and even disappearance of water flow in the drainage network (Lopez Bermudez 1999). Another is the seasonal dry up of wetlands (Sahuquillo & Lopez Camacho 1979, Llamas 1991, Romero et al 1997) with harmful effects on wetland ecosystems and peat conservation. Seasonally dried peats experience fast oxidation and subsidence processes (Garcia Rodriguez 1992).

Desertification threat on ‘La Mancha’ wetlands is particularly serious. Because of its prevailing climatic and geological conditions, the region includes 45 registered wetlands, of which 24 are targeted as internationally relevant conservation areas (Direccion General de Obras Hidraulicas 1994).