Ponencias Invitadas.-3. Methods and scales in soil erosion studies in Spain: problems and perspectives

Abstract

ABSTRACT Soil erosion is a major problem in some areas of Spain. Research groups have studied a variety of aspects of this problem in different environments, and at a range of scales using a diversity of methods, from piquettes and rainfall simulation to experimental plots, catchments and large regional areas. This has increased knowledge and identified the main problems: farmland abandonment, badland erosion, the effects of land use changes, and the role of extreme events and erosion in certain crops (particularly vineyards). However, comparison of results among various research groups has been difficult, posing problems in developing solutions from State and Regional administrators. The main problems arise from the use of differing scales, methods and study periods. Each scale is useful in analysis of a particular erosion process, but results obtained at small scales can not be easily upscaled. For instance, experimental plots can provide information on relationships among precipitation, runoff and sediment yield under different land uses, but no on rill or gully erosion, or sediment transfer to fluvial channels. In addition, the extreme interannual variability of Mediterranean precipitation makes it difficult to (i) compare erosion data from different periods, and (ii) elaborate comparable sediment balances. Soil erosion is a global problem with very complex causes, and potential solutions have political and social implications, and necessitate major changes in land management. Among issues involved, the effects of the changing policy on subsidies in the European Community, the consequences of local activities, the effects on soil erosion of changes in plant cover, the identification of eroded areas and their connectivity with the fluvial network, and the interrelations between the various sub-systems at a catchment scale. These issues require approaches at catchment or large basin scales, with finer scales (rainfall simulations, experimental plots) to address particular problems