Verifying Salinity Impacts on a Tropical Forested Wetland Using Multi-date TM Imagery

摘要

A recent study of the perceptions of local fishermen of the Teacapan-Agua Brava lagoon system, Mexico, suggests that considerable degradation of the mangrove forest has occurred. Furthermore, it has been postulated that the destruction is due primarily to hydrologic changes (increased salinity and tidal flow) associated with the construction of a canal built in 1972. To support the statements of the local peoples, three Landsat TM images (1986, 1993, 1999) were examined. A threshold mask derived from image differencing of a band 4/3 ratio was employed to provide quantitative data regarding wetland change. The results of this investigation strongly coincide with the accounts of the local fishermen. In 1986 approximately one-quarter of the mangroves under study were either dead or significantly stressed. By 1999, this figure had risen to one-third. These more recent changes may also be linked to the construction of yet another artificial channel and, indirectly, to a hurricane in 1994.