Ecological Degradation And Its Driving Forces Of The Huangqihai Wetland In China

Known as "the Earth’s kidney", wetlands provide various important ecosystem services and play an extremely important role in the carbon balance. However, wetland degradation has become a serious environmental issue, particularly in the arid and semi-arid regions. The agriculture and pasture interlaced zone (APIZ) in northern China is often close to the transition zone between arid and semi-arid regions, and it is extremely ecologically sensitive and vulnerable to global change. Influenced by the climate changes and human activities, wetlands have suffered great damage. Developing wetland ecosystem degradation analysis framework to analyze the wetland degradation process and its driving forces will provide a theoretical basis for research on the degradation and restoration of wetlands in ecological fragile areas.For this research, we chose the Huangqihai wetland in APIZ in northern China as the study area. Firstly, we analyzed Landsat MSS/TM/ETM+images ranging from1976to2011and associated historical records to quantify the fluctuation of the Huangqihai Lake. Secondly, we used geospatial technology to analyze the historical change in the wetland area and other land use/land cover of the Huangqihai Lake Basin derived from6periods (1976,1987,1993,1999,2006and2010) remote sensing images. We also chose landscape indices to analyze the landscape pattern of the basin. Finally, combining the natural and human factors in the Huangqihai Lake Basin, we tried to reveal the historical trends of environmental factors and the driving forces of wetland degradation through Mann-Kendall test, Sen’s Estimator test, Sequential Version Mann-Kendall test and Pearson Correlation Coefficient.Our results showed:(1) In1976, the area of the Huangqihai Lake was as large as67.6km2. In2006, the area covered only16.2km2, approximately24%of that in1976. It has been completely dry since2008.(2) During1976-2010, landscape fragmentation and landscape diversity increased in the Huangqihai Lake Basin. The area of wetlands decreased from193.5km2in1976to52.9km2in2010, and73%of wetland area had disappeared.(3) Before1999, the area of Huangqihai wetland was mainly driven by climatic conditions, and air temperature was the dominant factor. After1999, human activities were the key driver of the wetland degradation. Abundant water consumption caused depletion of the surface water. Excessive exploitation of groundwater resulted in wetland degradation caused by the lack of water recharging.The Huangqihai Lake Basin is confronted with a large variety of environmental issues, such as land reclamation, overgrazing, excessive groundwater extraction and salinization. An appropriate management needs to focus on the enhancement of water resource management and rationalization of the industrial structure in the basin, toward an effective water utilization and wetland conservation.