Land Use and Freshwater Ecosystems in France

Freshwater ecosystems have experienced over the last three decades larger declines in biodiversity than terrestrial and marine ecosystems. This is due to alterations of habitat, water pollution problems, overexploitation of water resources, exotic invasions, water extraction and flow regulation (Mantyka-Prigel et al., 2014). These human-induced pressures are mainly driven by land use changes. The increased urbanization and development cause the alteration of habitat in rivers. The agricultural sector is at the origin of diffuse pollution problems due to discharges of nitrogen, phosphorus and pesticides in soil and water. Some rivers in France are highly degraded because of these various land uses and their changes. This degradation is represented by a decline in the quality and quantity of water, and by changes in the distribution and structure of aquatic biota for some rivers in France (Oberdorff et al., 2002). This has led us to ask what land uses are at the origin of the spatial heterogeneity of the "health" of water bodies in France, and which public policies are best in improving it. The previous work on France has studied exclusively the effects of land uses on the chemical status of water quality. In this work, we close the gap in the literature by analyzing how alternative land uses affect freshwater ecosystems in France. In line with Hascic and Wu (2006), we estimate the effects of alternative land uses on a selected indicator of the ecological status of surface water, namely a fish-based index. As the effect of land uses on fish-based index is conditional to the location of water body and to its pedoclimatic conditions, it is important to take into account the spatial heterogeneity of the fish-based index in the econometric strategy. To this end, unlike the previous literature, we estimate a spatial econometric model to explain the FBI score registered for various monitoring points observed between 2001 and 2013 in France. We discuss the implications of the results for the design of agricultural and land use policies that improve the health of freshwater ecosystems. We first expect that different land uses (agriculture, forest, grassland, urban and other) and biophysical variables have a significant effect on the spatial distribution of the fish-based index. We also expect that the shares of forest and grassland areas in a specific hydrographic sector have a positive impact on the score of the fish-based index, while the shares of agricultural and urban areas have a negative impact. Furthermore, we expect that climatic variables significantly affect the evolution of the fish-based index over time. The findings of this study could be useful for policy makers to adapt land use policies for sustainable freshwater ecosystems.