MODELING THE GEOMORPHOLOGICAL IMPACT OF CLIMATIC VARIABILITY AND EXTREME EVENTS IN A SEMIARID ENVIRONMENT

The climate of the Mediterranean is marginal for many of the economic activities upon which the people of the region depend. Part of this ma rginality stems from the high inter-annual and medium-term variability in climate. This paper examines the impact of climatic variability on hydrology and vegetation cover using the PATTERN ecosystem model. Sig nificant inter-annual and medium-term variability in the components of the hydrological budget and in vegetation properties and process is a pparent in the results. An examination of the variability of soil eros ion which results from this variable hydrology and vegetation cover, i ndicates the temporally erratic nature of erosion events, the tendency for most erosion to occur in very few extreme events, and the dynamic response of erosion to climatic variability. The results also indicat e the dependence of erosion on the type of vegetation cover and vegeta tion response to climatic variability. I conclude with the observation that the majority of significant soil erosion events in Castilla La M ancha (CLM)-site of the EFEDA I and EFEDA II research projects-occur a s a result of extreme precipitation events rather than slow progressiv e land degradation. In this way, soil erosion can be a poor indicator of land degradation. Badlands are the relic of past climatic extremes and not necessarily an indicator of present-day desertification. (C) 1 998 Elsevier Science B.V. All rights reserved.