Scale and ecological dependence of ecosystem services evaluation: Spatial extension and economic value of freshwater ecosystems in Italy

Using land cover datasets derived from satellite imagery as a proxy for ecosystem services (ES) mapping and evaluation generates a series of technical problems mainly related to the resolution at which spatial data are acquired. Small sized and highly fragmented ecosystems such as wetlands, streams and rivers are particularly underestimated when coarse resolution land cover datasets are used. However, even at finer resolution, a large fraction of the economic value provided by freshwater ecosystems may not be adequately captured by remote sensed data because, other than technical and methodological problems, the provision of many freshwater services is strictly dependent on the interactions and contacts of these ecosystems with contiguous environments. The paper analyzes and discusses the effectiveness of the CORINE land cover (CLC) dataset to represent the spatial extension and, indirectly, the economic value of freshwater biomes in Italy, with emphasis on rivers and streams. Using a georeferenced national hydrographic network database and applying a stream buffer of variable width to more than 20,000 water courses, we demonstrated that less than 10% of the estimated surface is captured by the CLC dataset with heavy negative consequences on the overall evaluation of ES at local, regional and national scale. Our approach, easily applicable also to other geographical and spatial contexts, may contribute to improve proxy-based methodologies in ES mapping/evaluation and may help to limit errors in the estimation of freshwater services. (C) 2013 Elsevier Ltd. All rights reserved.