Wetland loss under the impact of agricultural development in the Sanjiang Plain, NE China.

Wetland loss has been the major environmental problem in Sanjiang Plain, NE China in recent years because of the dramatic agricultural development. We determined the spatial associations of the wetland loss rates in an 11,000-km(2) study area for two intervals of period 1 (1975-1989) and period 2 (1989-2004) spanning 30 years by using geographic information systems. The landscape of this area was simple with five categories, composed of ten types, and including three natural wetland types--open water, marsh, and wet meadow. Extensive agriculture was the principal cultivation form in terms of large size farm units in the area. Agriculture has become the principal land use category replacing natural wetlands over the 30-year period. It has changed the whole landscape of the region and the landscape pattern, causing wetland loss and fragmentation. The wetland loss rate of the area was very different between the two intervals, while wetland loss was not uniform throughout the region and was influenced by the landscape characteristics, such as topography, geomorphology, and the location of the wetlands in the watershed. Despite the remarkable land use changes, the wetlands distribution in the landscapes was similar compared to their original pattern. These results indicated that agricultural development affected the areas more than the distribution pattern of the wetlands in this region.