Methodological limitations of CLC to assess land cover changes in coastal environments

Abstract

CORINE land cover (CLC) is used to analyze the state and evolution of land covers in the coastal zone, which is recognized as one of the most important ecosystems providing a wide range of services to human societies. CLC data were processed and spatially analyzed using GIS to study land cover changes in an area of 10 km landwards from the coastline along the Iberian Peninsula, including contrasted coastal zones in Portugal and Spain. A series of methodological limitations arising from the results of this study were investigated. In particular, we concentrated on the effect that spatial definition, delimitation of the coastline, characterization and delimitation of wetlands and water bodies, and the coherence in land cover changes exerted on the pattern and magnitude of land cover temporal changes. For example, in Galicia, “water courses” apparently increased by 520% whereas “intertidal flats” were reduced by 77% between 2000 and 2006. In Northern Portugal, “salt marshes” increased by 40% and “coastal lagoons” decreased by 90% over the same period. The effect of these different delimitations would represent a 30% increase in the Galician coastline length. Some ancillary data such as topographic maps, orthophotographs or satellite imagery are presented as a necessary complement to accurately estimate land cover changes and some methodological cautions are discussed.