Landscape dynamics and driving forces of wetlands in the Tumen River Basin of China over the past 50 years

Human activity together with climatic changes have resulted in the substantial loss of wetlands in the Tumen River Basin of China in the past five decades. In this study, the landscape dynamics of wetlands upstream, midstream and downstream of the Tumen River Basin from 1960 to 2009 were investigated using remote sensing and geographic information systems. Analytical methods, such as dynamic degree, transfer matrix and indices, e.g., patch number (NP), area percentage of landscape patches, mean patch size, patch density, Shannon’s diversity index (SHDI), and Shannon’s evenness index (SHEI), were utilized to describe the landscape dynamics. The results showed that over the past 50 years, human-made wetlands, including paddy fields and reservoirs, increased, whereas natural wetlands, including marshes, lakes and rivers, decreased. In the study period, a large number of natural wetlands were converted by humans into other types of wetlands and non-wetlands. For wetland landscape changes, the NP, landscape fragmentation index, and SHEI increased, whereas the average patch area and SHDI decreased. In addition, we found that human factors were the main driving forces for the reduction of natural wetlands in this area, among which agricultural activities had the strongest impact. Great losses of natural wetlands have led to ecological problems in the region, such as a decline in biodiversity and soil degradation.