Connectivity dynamics in contemporary farming systems

1A1AIn the European Union current agricultural policies aim at creating semi-natural elements in areas of intensive production. Objectives are to maintain or restore biodiversity in open landscapes and to protect surface water resources. Current state of most European agricultural landscapes is a high degree of fragmentation of habitats and a consecutive low connectivity. We looked at the effects of the new CAP (Common Agricultural Policy) on a long term ecological research site in northern Brittany, France. Herbaceous strips 5 to 10 m wide are sown along permanent streams, and at least 3 percent of a farm territory has to be semi natural habitat. Habitat quality may vary according to the diversity of sown species and to management practices and techniques. We use simulation models to assess connectivity according to different scenario of implementation of CAP in one landscape. Connectivity is measured for species differing by their dispersal ability and habitat requirement (habitat type, size, and complementation among habitats). In all the cases the new scheme leads to an increase of connectivity at the landscape level, but the effect of the spatial distribution of novel habitats and management practices (date of mowing within the vegetative cycle leaving flowers or not) are determinant to increase it. The combined effects of landscape structure and habitat quality emphasize the necessity to plan and carry biodiversity management at several scales