Variations of Coastal Wetland Landscapes in the Pearl River Delta in the Last 20 Years

Wetland types and landscape variations in the Pearl River Delta(PRD) during the last 20 years(from 1986 to 2005) were studied based on 4 Landsat TM satelite remote sensing images.The results show that the Pearl River estuary has been influenced intensively by the human activities,and the wetland area can only make up less than half of the whole coastal area.Even within the wetlands,the most are the artificial wetlands.Since 1986,the types of wetlands have changed distinctly.The land area used for the human constructions increases greatly,whereas the wetland area increased slowly before 2000 and decreased after 2000.The change in the wetland lanscape index is relatively small and the diversity index,the evenness index and the fractal dimension index tend to decrease slightly.The richness index and the habitat fragmentation index also increase slightly.However,the gallery density index decreases notably.A degradation of the coastal wetlands occurrs,to some extent,in the Pearl River estuary.Particuarly after 2000,the degradation of the coastal wetlands tended to intensify.Therefore,the pretection and restoration to the coastal wetlands,especially to the natural wetlands,should be enhanced.