黑河中下游绿洲生态安全评价

Ecological security assessment for the oases in the middle and lower Heiher River

生态安全包括自然生态安全、经济生态安全和社会生态安全 ,尤指自然和半自然生态系统的安全 ,即生态系统完整性和健康的整体水平反映。生态安全是维护地区或国家乃至全球的生态环境不受威胁的状态 ,能为整个生态经济系统的持续发展提供生态保障。从水安全、土地安全、经济社会安全出发 ,选取水资源量供需比、地表水质量、地下水埋深和地下水矿化度 4种水安全评价指标 ;土地人口承载度、林地覆盖率、草地载畜度、绿洲面积变化率、绿洲土地沙化率、绿洲土地盐碱化率和抗灾度等 7种土地安全评价指标 ;人均 GDP产值、单位面积农业生产总值、农民人均纯收入、绿洲人口密度、城市化率和文明度等经济社会安全评价指标 ;共计 17项 ,建立了绿洲生态安全评价综合指标体系。然后 ,应用综合评价法、层次分析法和 GIS等多种方法与手段 ,在绿洲尺度上对黑河干流中下游地区的张掖、临泽、高台、鼎新和额济纳 5个绿洲进行绿洲生态安全综合评价。评价结果显示 :自黑河中游至下游 ,各个绿洲的生态安全状况依次降低 ,最下游的额济纳绿洲生态安全仅为 4级的差状态。其中 ,水安全是关键 ,土地安全是载体 ,经济社会安全是保障 ,以上几方面相互关联 ,共同作用导致绿洲的生态安全综合水平。

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.