Land use and land cover change analysis in predominantly man-made coastal wetlands: towards a methodological framework

In areas with a long history of human occupation, coastal wetlands have undergone extensive modification to accommodate extractive activities as salt-extraction and aquaculture. These man-made wetlands maintain some of the ecological functions of natural wetlands in spite of their artificial character: their suitability as complimentary waterbird habitat is well documented. In cases of wetlands composed of mixed natural and man-made areas, similarities in substrate-vegetation-water compositions may pose challenges in the applicability of remote sensing and GIS techniques for the study of landscape changes, requiring tailor-made, case-specific methods. We explored this supposition by testing these techniques for the study of the Bahia de Cadiz Nature Park (Spain). Using Landsat imagery spanning the 1985-2011 period, natural and man-made marsh areas were classified separately and results merged to produce land cover classification maps. Different change dynamics were observed for the natural and man-made areas, the latter exhibiting prominent changes, including widespread vegetative succession. Further, through the overlay of ancillary land use data for 2011, an integrated land use and cover map was produced for this year. Different scenarios arising from the abandonment of extractive activity and structural negligence were highlighted. Furthermore, a methodological framework for the classification of predominantly man-made wetlands was designed. The method is cost-effective and open for integration of additional datasets, and is considered a beneficial input to conservation and land use management. Its applicability for monitoring of landscape change not only pertains to the study area, but also extends to other coastal wetland areas of a similar nature.