LAND USE CHANGE DETECTION AS A BASIS FOR ANALYSING DESERTIFICATION PROCESSES : A CASE STUDY IN TABERNAS

This contribution proposes an integrated approach to detect and quantify land-use and land-cover changes as a basis for studying and predicting changes in environmental processes leading to desertification. The approach has been applied in Tabernas (Almería, Southeast Spain), a representative area of the Mediterranean region where a combination of extreme environmental conditions and modifications of the land-use pattern that occurred in the last decades have led to increase the risk of desertification. The approach is based on multi temporal records of remotely sensed data and field survey. Sets of aerial photographs taken in the fifties (1956), the eighties (1981) and the nineties (1995) were used to map land use and cover in the three different periods of the last fifty years. The results indicate that from 1956 to 2000, a total area of 5218 hectares of land was subjected to change in land use. The main land cover type that was subjected to change was dry farming. Throughout the past four and half decades 2507 hectares (32%) of dry farming has changed into different land use types, of which 1447.7 (57.7%) hectares changed to irrigated farmland, 857 (34%) became abandoned and about 202 (8.3%) were subjected to various activities (infrastructures, industries, etc.) that have left the area without a vegetation cover. The abandoned areas have evolved to areas with a weed type non-permanent bush cover, which is totally different from the natural cover in the region. The land abandonment and the change from dry farming to irrigation seem to exert pressure on the environment, that can lead to an increase in desertification processes such as soil erosion, salinisation and pollution. Most of the recent irrigated farms are on slopes ranging in inclination from 2 to 8%. Important erosion processes can occur both on these slopes and on abandoned areas depending on other influencing factors (e.g., soil erodibility).