Analysis on Wetland Change before and behind Implementing the Project of Returning Farmland to Lake in Dongting Lake Region

Wetland change and its succession rules were studied by analyzing the TM remote sensing images of two periods,1996 and 2004,which are before and behind implementing the project of returning farmland to lake.The result showed that the area of wetland in Dongting Lake region was heavily decreased by 3 753.99 km2,in which natural wetland decreased by 1 213.19 km2 and conducted wetland decrease with 2 540.80 km2.The wetland change in reclamation area presented that the area of constructed wetland(cropland) reduced in a large scale and dry land sharply increased,as well as the area of reed and forest increased.The wetland change in outer lake region presented that the area of natural wetland decreased,and the area of forest quickly increased by the reduction of the area of sedge land,as well as forest land continuously extended to mudflat.The project of returning farmland to lake released the reduction of wetland to same extends,but the phenomenon of reclaiming lake to farmland still happened in Dongting Lake region.Therefore,the whole wetland was still suffering form degradation.