Abstract: The study with satellite remote sensing technique and Costanza method showed that from 1984 to 2003,the total area of various ecosystems in the coastal tidal zone of Dongtai City,Jiangsu Province increased from 108.54 to 171.31 km² or by 57.83% due to natural siltation,of which,the area of natural ecosystem decreased from 60.82 to 21.64 km² or by 64.42%,while that of artificial ecosystem increased from 47.72 to 195.23 km² or by 309.12%. During the same period,the total value of ecosystem services in this zone increased by 76.96%,with natural ecosystem services value dropped from 56.26×10⁴ to 17.19×10⁴ US$ or by 69.45%,while artificial ecosystem services value raised from 40.55×10⁴ to 154.13×10⁴ US$ or by 280.10%. The decrease of natural ecosystem area and the increase of artificial ecosystem area illustrated clearly that the costal tidal ecosystem of this city was being degenerated seriously,and the decline of natural ecosystem services value was resulted from this degradation and the decrease of natural ecosystem area.

Key words: Water supply from forested land, Water consumption by forest trees, Forest evapotranspiration, Water consumption character, Water balance, Protection forest