Mangrove research and coastal ecosystem studies with SPOT-4 HRVIR and TERRA ASTER in the Arabian Gulf

Mangroves reach their optimal development in the wet tropics although some little known mangrove stands are reported in subtropical arid coastlines especially from the Red Sea to Pakistan where they form one of the driest mangrove habitats in the world. Because they constitute the only available evergreen forest in hyper-arid warm coastal areas, the main wetlands for migratory birds and essential nursery ground for many species of fish, it is imperative to produce a sufficiently accurate map for monitoring their changes and for their protection. The main objective of the present work is to test and to select the best methodological approach to discriminate and map the mangroves and related coastal ecosystems in the United Arab Emirates (UAE), between Abu Dhabi and Dubai, a coastal stretch about 750?km long. It was found that the best practical results were produced by the Maximum Likelihood and Mahalanobis classifications although some limitations remain unsolved, especially in open ecosystems, which are common in arid areas. Moreover, SPOT-4 High-Resolution Visible Infra-Red (HRVIR) data proves at least as efficient as TERRA ASTER data, in spite of a slightly finer ground resolution and the great number of channels for ASTER. Ultimately, the most appropriate working scale for mapping coastal habitats, compatible with pixel size, is in the order of 1/25 000.