The Common Agricultural Policy (CAP) of the European Union, technological developments, and commercial pressures to maximise returns and minimise costs, have given rise to a marked intensification of agriculture, particularly in the last 30 years. This highly intensified agriculture has resulted in environmental problems such as erosion. More recently, the CAP reform has introduced agri-environmental measures as a means of combating soil erosion. However, even though the 1992 CAP reform was meant to contribute to overall grassland stabilisation, recent studies point to continued agronomic pressures to plough up grassland. This paper presents a brief synthesis of crop trends and environmental impacts on erosion in Upper Normandy, France. Our analysis is based on data from the French agricultural censuses and on some remote sensing results from the FLOODGEN European project. We also used the simulation capacity of the runoff and erosion STREAM model to test the consequences of grassland decrease in agricultural catchments and to show the efficiency of some agri-environmental measures. Results show that Upper Normandy has lost 200,000 ha of permanent grassland between 1970 and 2000. A simulation performed with the STREAM model shows that the ploughing up of 17% of permanent grassland leads to a sharp rise both in runoff volume (>75%) and soil loss (>85%) within a catchment basin.