Wetlands, forests and oceans form the three global ecosystems. Wetlands are the natural integration of aquatic and semi-aquatic organisms in a wet environment, and they have a unique structure and function. Wetlands are an important natural resource and one of the most important environments for humans. They not only offer the resources necessary for human survival but also play an important role in ameliorating weather conditions, flood storage, and the control and reduction of environmental pollution. Wetlands have thus been called the "kidney of the earth". However, due to increased human activities and lack of understanding of the functions and values of wetlands, most wetlands have been unsustainably exploited and/or destroyed in the last few decades. From the start of human civilization, wetlands have been targets of land development. Reclaiming land from lakes and large-scale agricultural development in wetlands causes tremendous change in wetland landscapes and results in serious environmental problems. Such problems have finally drawn our attention to the value of these ecosystems. Increasingly, research has investigated the relationships between human activities and changes in wetland landscape patterns and the climate. The health of the Tumen River region wetland ecosystem is locally and regionally important in Northeast Asia.
In this paper, we summarize the current health conditions of national and international wetland eco-systems, and establish an evaluation system for ecological health, suitable for the wetland ecosystem of the lower reaches of the Tumen River. In this system, a health assessment index for wetland ecosystems is constructed based on five health stage criteria:primary health; health; secondary health; general sickness and disease, and by combining wetland characteristics using pressure-status-response models. The system is divided into three item layers and eight factor layers, with 30 indicators in total, and provides quantitative standard values for each indicator. The index system includes several major indicators including those reflecting physics, chemistry, biology, landscape features, ecology, socio-economy, and human health. The weight of each index is calculated using an analytic hierarchy process and then the final index value calculated using a three-step, fuzzy, comprehensive evaluation method. An index value of 0.5878 was obtained as the overall health index of the wetland ecosystem in the lower reaches of Tumen River, which can be categorized as a sub-healthy state. The health index for the pressure system was 0.5292, the response system was 0.6866, and the state system was 0.5116. The membership at each level was 16.83%, 25.37%, 16.76%, 16.97%, and 24.07%.
The factors lowering the ecological health of the wetlands in the lower reaches of Tumen River are:the poor quality of water replenishing the wetlands resulting in serious water pollution, severe eutrophication; the degradation of the wetland area influenced by human factors; the fragmentation of the landscape and the decline in productivity levels. These factors have ultimately reduced the resistance of this wetland ecosystem, and thus increased the vulnerability of the wetland to certain threats. Based on analyses of the underlying causes of these threats, strategies for health protection, recovery and sustainable development of the wetland ecosystem of the lower reaches of the Tumen River are proposed. Wetlands in this region need science-based conservation and management.