Study On Urban Ecological Risk Assessment

The ecological risk assessment is a new research field, which has been rising and developing with the change of environment management objectives and environment conception. It makes use of comprehensive knowledge in disciplines involving environmental science, ecology, geography, biology etc., and adopts mathematical and statistical techniques to forecast, analyze and assess the probable losses of ecosystem or its components caused by uncertain disasters or events. Currently, studies on ecological risk assessment especially on that for natural water area are relatively rich abroad and are in the process towards a mature system. Domestic research, started in 1990's, has obtained considerable achievement through numerous researchers'efforts.The urban ecosystem is a compound system of natural, social and economical elements. It makes human producing and living activities as its core and consists of residents and urban environment. Urban ecological risk refers to the potential likelihood, in process of city construction and development, of any negative impact on natural, social and economical urban subsystems. The impacts were caused by human activities and violent natural changes.Under the direction of the relevant indicators concerning ecological city constructing and urban sustainable development monitoring, and according to the "environment-economy-society" framework, the study establishes a four-hierarchy indicator system for urban ecological risk assessment. The indicator system contains 3 first-layer indicators (environmental ecologicalized level, economical ecologicalized level and social ecologicalized level) and further 7 second-layer,21 third-layer and 62 forth-layer indicators.Then approaches of Delphi and AHP are employed to identify the weight of each indicator in each hierarchy. The quality indexes and the level indexes for both positive and negative ecological factors are defined as well.The indicator system is applied in the case of Zhuhai city. Viewed from perspectives as atmosphere, water body, forest, noise and ocean, the ecological environment of Zhuhai city is analyzed both qualitatively and quantitatively. The results indicate that the current environment quality index (EQI) of the city is88.43, more specifically, the quality indexes for atmosphere, water body, forest, noise and ocean are91.88,81.55,85.00,100.00 and 86.2 respectively. Moreover, based on assessment on the state of the city's environment examination, forest preservation and pollution management etc., the environment management level index (EMLI) for the city is identified as 89.00; assessment on the city's infrastructure construction, forestry construction and legal system for environmental protection is conducted as well, presenting a value of 86.92 for the environment construction level index (ECLI). A value of 88.27, as the environment ecologicalized level of the city, can be drawn from synthesizing the EQI, EMLI and ECLI. When it comes to economy-related evaluation, the study suggests that the economic growth mode (in terms of economy development level and energy depletion) value is 86.33 and the industry ecologicalized level is 71.64, resulting in an ultimate economical ecologicalized level of 74.77 for Zhuhai city. In the same way, the study concludes the social ecologicalized level of the city is 73.81, through synthesized assessing the scale of city population, the living standard of residents, the transportation mode of the city and the residents' residence mode and their consciousness for environment protection.According to the obtained indexes of environmental ecologicalized level, economical ecologicalized level and social ecologicalized level, the current ecological risk index for Zhuhai city is identified as 0.2122, which falls in a low-risk range. However, it means a risk in exist. To aim at that, the study puts forward a series of risk managing strategies and, accordingly, forecasts the city's ecological risk in the following 15 years:0.1256 in 2010, 0.0673 in 2015 and 0.0412 in 2020.The study adopts three-layer B/S model thus develops software for ecological risk assessment. The software can realize a range of main functions such as user management, data management, risk assessment, data browse, on-line expert comment and news release, laying a solid foundation for the extensive application of the urban ecological risk assessment system.The major innovation points of the paper are as follows:1. A four-hierarchy indicator system, containing 3 first-layer,7 second-layer,21 third-layer and 62 forth-layer indicators, is established for urban ecological risk assessment. The weight of each indicator in each hierarchy is calculated as well.2. A set of quality indexes and level indexes for ecological factors are defined, and the functional relationships between the indexes and their influence factors are built up.3. The study serves as the first systematic and overall assessment on the ecological risk of Zhuhai city. It utilizes remote sensing (RS) techniques to collect and analyze the information about the city's vegetation types and greenland species. Consequently, according to the established indicator system and based on the calculated indexes for environmental ecologicalized level, economical ecologicalized level and social ecologicalized level, the study concludes that the ecological risk of Zhuhai city is 0.1883, which belongs to a low risk range while still suggests existing ecological pressure.4. The researchers innovatively develop software for urban ecological risk assessment, contributing to the further application of the established risk assessment system.