The effect of land use on runoff and soil erosion rates under Mediterranean conditions

The effect of land use and precipitation on annual runoff and sediment loss was investigated in eight different sites along the northern Mediterranean region and the Atlantic coastline located in Portugal, Spain, France, Italy and Greece. These sites represent a variety of landscapes and are under a number of land-uses representative of the Mediterranean region, such as agricultural land with rainfed cereals, vines, olives, eucalyptus plantation or natural vegetation (shrubland). It was found that land use can greatly affect runoff and soil erosion. The greatest rates of runoff and sediment loss were measured in hilly areas under vines (average sediment loss 142.8 t km−2 yr−1). Areas cultivated with wheat are sensitive to erosion, especially during winter, generating intermediate amounts of runoff and sediment loss (17.6 t km−2 yr−1) especially under rainfalls higher than 280 mm per year. Olives grown under semi-natural conditions, as for example with an understory of vegetation of annual plants greatly restrict soil loss to nil values (0.8 t km−2 yr−1). Erosion in shrublands increased with decreasing annual rainfall to values in the range 280–300 mm and then it decreased with decreasing rainfall (average sediment loss 6.7 t km−2 yr−1).