| Arid-oasis areas become even more critical as1/3of the Chinese population lives in arid-oasis regions in recent years. From long-term sustainable economic development point of view, it is important to build an eco-risk assessment method fit for assessing arid-oasis areas by using regional eco-risk assessment theory. Arid-oasis area has typical landscape types different from other eco-system. Oasis land degradated these years because of the long term human impacts and nature disaster, which is different from the city areas and developed areas. So the previous method and technical system could not be a guid to conduct the arid-oasis assessment. Based on landscape ecological features of arid-oasis area and by using3S. our study attempts to construct an eco-risk assessment technical system to assess the potential risk caused by natural disaster and human activities in arid-oasis areas. The technical system could assess the change in the time series and spatial distribution. Finally, we conducted a study on the eco-risk assessment in the Heihe River Basin, which is a typical arid-oasis ecosystem in China, to verify the feasibility, intuition and generality of the technical system.The study concluded following two parts:1) Construct a eco-risk assessment technical systemIn the theory research part, on the one hand, we modified the framework for eco-risk assessment conducted by the U.S.EPA, as a guidline to assess the eco-risk in arid-oasis areas. On the other hand, this paper constructed a eco-risk assessment technical system. The whole process is based on six major elements, the purpose of the assessment concerned by the risk manager and risk assessor, conceptual model characterizing risk and the assessment end point, tools of data procurement and data analysis, index system characterized the effects and the exposure, uncertainty analysis and final result of the eco-risk, including the change on the time series and the spatial distribution.2) Comparative study on the applicationTo verify the feasibility, intuition and generality of the technical system conducted in the front part, we did a case study on The Heihe River Basin. The Heihe River Basin is located at98°00- 101°30’E,38°00’-42°30’N and has a drainage area of130,000km2. It consists of the upper mountainous area, the Middle Oasis area, and the lower terminal arid Oasis-Gobi-desert area. This paper focuses on the middle Oasis area, including8counties, Jinta, Jiuquan, Jiayuguan, Gaotai, Linze, Zhangye, Shandan, Mingle. This area has the The highest population density and the typical area influenced by the human activities and natural disaster.In this case study, based on advanced remote sensing and Geographic Information Systems (GIS) technologies, the influences of precipitation, human activity and vegetation sensitivity are evaluated. The change of landscape index system could assess the eco-risk of The Heihe River Basin. The final value of eco-risk is classified into five levels: extreme low, low, moderate, high and extreme high. The results including:①The landscape eco-risk value (ERI) of the Heihe River Basin decreased from0.83to0.60, from the high-risk level down to the middle level. The results can be attributed to the better living conditions, the effective policy of environmental protection and effective Ecological Restoration over these years.②The spatial distribution could be divided into3regions, the high risk level region was influenced by the erosion of desert and water loss and soil erosion. For example, the northern area of the Heihe River Basin was in higher risk than other areas because where is next to the Badan Jara Desert and has been subjected to erosion due to scarce vegetation and serious water shortage in the past10years. The middle level region was influenced mainly by the human activities and natural erosion. The extreme low area was mainly influenced by the human activities.③The structure stability of landscape is decreased from0.48to0.41because of the decreasing landscape dominance and landscape diversity and increasing fragmentation.④The first net productivity index increased from0.67to0.94because of the better living conditions.⑤Finally, we can concluded that, from the results above, the eco-system of The Heihe River Basin Toward a more favorable direction In the final research, we conducted a comparative study. Our study showed that, the research method constructed in this study can objectively detect the spatial distribution of the landscape risk values in the arid oasis area and the time series change of the eco-risk. It could play a positive role in the future arid-oasis ecosystem eco-risk assessment and assist future environmental management. |
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