城市综合生态风险评价——以淮北市城区为例

城市面临复杂的生态风险,为了保障城市安全,需要对单一灾害或污染源的生态风险评估结果进行整合。基于城市复合生态系统特性,将当前城市地域常见的生态风险区分为自然灾害、环境污染及生态退化等3种主要类型,以土地利用单元作为风险受体,整合自然、人文、景观及环境因子,在现有生态风险评价研究方法基础上,构建了城市综合生态风险评价的空间分析框架。研究中选择淮北市城区作为研究区,针对研究区内存在的洪涝、干旱、水污染、大气污染、采煤塌陷及生态服务降低等生态风险类型,定量评价其空间差异,并提出相应的风险防范措施。案例分析结果表明,研究区综合生态风险较高的区域包括龙河、岱河、龙岱河与闸河等过境河流流经塌陷密集带的河段,北湖、东湖、中湖及南湖等人工湖泊沿岸,化家湖湖岸,及土型、新蔡、北杨新杨煤矿及其外围地区。由降低生态风险保障城市生态安全角度,在未来城市的整体规划中,建议结合城市外围绿地与城市内部的高风险区域,划设禁建或限建区域,共同构建淮北城市生态风险防范的空间结构。

Comprehensive assessment of urban ecological risks: the case of Huaibei City

Ecological risk is defined as the probability that a specific population, landscape, or ecosystem in a dangerous environment has its health, productivity, hereditary features, or economic and aesthetic values affected. Various and complex ecological risks occur widely in urban ecosystem. Conventional assessments for single types of ecological risks are not comprehensive enough to evaluate the degree of ecological risk, and are also unsuitable to meet the multiple needs of sustainable urban development and management. In this paper, a research framework has been formulated to evaluate urban ecological risks spatially and more comprehensively. The framework has five steps: identification of potential risk types, selection of influential factors, exposure analysis, effect analysis, and putting forward of mitigation measures. First, three primary kinds of ecological risks, including natural disasters, environmental pollution, and ecological degeneration are considered. Selecting factors of the natural environment, social economy, landscape, and pollution would be used to explain the influence of spatial characteristics. Exposure analysis showed frequency, range, and duration of each risk based on the weather record, Annual Report of Environment Quality, and other statistical data from government departments. The effect analysis integrated the results of exposure degree, effect of environmental factors, and degree of vulnerability. Degree of vulnerability depends on risk object characteristics. Land use unit is suitable to be the object for illustrating the degree of risk influence directly and linking with urban planning. Considering function and land cover, land use types would be categorized as high density building area, medium density building area, low density building area, traffic land, forest land, grassland, cultivated land, garden land, water, and unused land. The urban core area of Huaibei city has been chosen to test this framework. Major ecological risks in Huaibei include flood, drought, water pollution, air pollution, land subsidence, and ecological service degradation. Single and comprehensive ecological risk degrees have been calculated. Based on these, spatial strategies of urban ecological planning are proposed that incorporate these assessment results. Three risk levels were recognized in this study area by our comprehensive ecological risk assessment. In high risk areas land use for urban expansion and construction should be limited in future planning, vegetation cover should be restored, and climate change and environmental quality should be monitored to protect the urban ecological environment and the lives and health of human beings. Medium risk areas require a different building code for each risk category when building and constructing to ensure the safety of infrastructure such as traffic, energy, and water. Furthermore, an environmental impact assessment should be undertaken and approved to guide building. High density development should be limited to low risk areas, although the need for land use management after planning remains. The framework of comprehensive ecological risk assessment integrated different risks of natural disasters, environmental pollution, and ecological degeneration. Land use units have been used as the risk objects and which can be directly used as the ecological background for urban planning in the future. Also, it is simple to adjust when land use changes, and when different planning scenarios require new decisions. Furthermore, it can highlight spatial variation of ecological risks and make suggestions for efficient mitigation. There are still some difficulties in the study, i.e. the considerations of the degree of vulnerability are complicated, and have to integrate the opinions of experts, local residents, and governments. For governments, the degree of vulnerability is linked with financial expenditure; for residents, it depends on the safety of life and belongings; and for different experts, it involves natural capital, environmental quality, human health, and so on.