A study on the wetland dynamics and its main driving factors in Sanjiang plain, Northeast China

Agricultural activities, especially reclamation, are considered major threats to the wetland ecosystems in Sanjiang Plain, the largest concentrated area of the freshwater wetlands in China. Using remote sensing date interpretation, we obtained land cover sceneries for 1976, 1986, 1995 and 2005. Based on these data sets, this study analyzed the dynamics of the wetland cover and the conversion between wetland and other land cover types for Sanjiang Plain during the past 30 years. It shows that the wetland in Sanjiang Plain has been severely damaged. The wetland area decreased by 37.72% from 1976 to 1986, by 15.54% from 1986 to 1995, and by 30.97% from 1995 to 2005, Wetland loss had much slowed down during 1986 to 1995, but in recent years (1995-2005), it was very high. It was found that most wetland losing was the result of cropland reclamation, and only small part due to conversion into grassland and forests. Both demographic and resource management policies were analyzed for the wetland reduction. The result showed that increasing population was the main reason for wetland reduction in the past decades since P.R. of China foundation. Though the speed of wetland loss decreased during the later period, the reclamation of wetland still happened, so the practicable protection measurement of the wetland in Sanjiang Plain should be reinforced further.