Ecological security assessment for the oases in the middle and lower Heiher River
黑河中下游绿洲生态安全评价

Ecological security includes the natural ecological security, the economic ecological security and the social ecological security. The particular points of the natural and semi-natural ecosystem security encompass the integrity and health of the ecosystem. The ecological security describes a state that the area, the country and even the global ecological environment are not threatened. It will provide the ecological guarantee for the sustainable development of the whole ecological economic system. This paper chooses seventeen indexes from water security, land security, and economic-social security to set up the comprehensive index system of the ecological security assessment of the five oases, which are Zhangye, Linze, Gaotai, Dingxin and Ejina in the middle and lower reaches of the Heihe River. These indexes includes the ratio of supply to demand of water, the surface water quality, the depth of groundwater, the mineralization of groundwater, the people load of the land, the percentage of forest coverage, the animal load of grassland, the rate of the oasis area change, the rate of desertification in every oasis, the percentage of salinized land in oases, the calamity resistance capability; the GDP per capita, the gross agricultural output per unit, the net income per farmer, the population density of the oases, the rate of the city urbanization, and the rate of civilization. Then the paper uses various methods and means such as comprehensive evaluation method, AHP (the analytic hierarchy process) and GIS (the geographic information system) to comprehensively assess the ecological security state of the five oases. The conclusion is that the oasis ecological state from the middle to the lower reaches of Heihe River has greatly degenerated. Among the five oases, Ejina oasis has the lowest value. We can also conclude that the water security is the key point, land security is the carrier, and economic social security is the guarantee. These three aspects relate each other, which makes for the states of the whole ecological economic system.