Urban Ecosystem Health Assessment

Since early 20th century, our environment has been affected with large scale and high intensity, and the natural ecosystem has been changed or damaged. As a result, ecosystem health is suffering increasing stress, and the development of human beings is in danger. Health and relative stability of ecosystem are necessary to human survival and development. It is very important to maintain ecosystem health and its well-circulation. In the last 10 years, the concept of ecosystem health was brought forward and has become the new focus and most active front in ecology studies. Abroad, ecosystem health studies on agro-ecosystem, hydro-ecosystem, forest ecosystem and urban ecosystem, et al., have been developed. In recent years ecosystem health has also got more attention at home, but study on urban ecosystem health is still out of sight. Ecosystem health is a new research field without very commonly accepted concepts, assessment theory and analytical approaches. Especially for urban ecosystem health, many aspects are in starting point. In the thesis, the theory, methodology and practice of urban ecosystem health analysis are explored deeply. I start with analyzing the types, factors and effects of the stresses to urban ecosystem health. By estimating urban ecological footprint, the stress to urban ecosystem health is reflected from the side face. Then the concept of urban ecosystem health is clearly defined, and based on which, the ecology urban ecosystem health assessment theory and method are put forward. Finally, the case study in Guangzhou is done. The main content and results are as follows: (1) Stress and Urban ecosystem health The stress of human activity is important content of urban ecosystem health assessment. The factors causing urban ecosystem stress includes over-exploiting natural resources, irrational industry and land use pattern, and lavish life style. Urban ecosystem footprint is an index representing the occupied area of natural ecosystem (such as argo-ecosystem, forest ecosystem and marine ecosystem) by urban development. By estimating the ecological footprint of Guangzhou city, urban ecological footprint is found much bigger than its own area, and will increase in the future. This suggests that the stress of human activity in urban area to urban itself and outside natural ecosystem is great, and the health situation of urban ecosystem should be paid to more attention. (2) Defining urban ecosystem health Currently, there was no clear and consistent definition of urban ecosystem health professionally before this study. According to summary of the concepts for general ecosystem health and analyzing the characteristics of urban ecosystem, a healthy ecosystem can be seen from two aspects: On the one hand, this natural-economic-social compound ecosystem should be stable, sustainable, and resistant to outside stresses ecologically. On the other hand, urban ecosystem should, from social-economy point of view, have the ability to provide citizens sustainable ecosystem services. Healthy ecosystem is characterized as vitality, vigor, structure with biodiversity and equilibrium and should function with efficiency and less waste. (3) Theory of urban ecosystem health assessment Urban ecosystem health study is a multi-disciplinary subject which overlaps ecosystem ecology, health science, system science and urban ecology etc. According to hierarchy theory, temporal-spatial theory, urban ecology, system ecology and system engineering, some relative concepts used in urban ecosystem health assessment are analyzed. These theories provide good guidance to creating the approach and the practice of urban ecosystem health assessment. (4) Methodology of urban ecosystem health assessment There is no generally acknowledged method to assess ecosystem health, especially for urban ecosystem health. Based on urban ecosystem assessment theory, using the general ecosystem health standard given by Rapport for reference, the author build an initial indicator system for urban ecosystem health assessment, and filter those indicators with redundancy information. Then the final index system formed. By using the fuzzy mathematics method, the model of urban ecosystem health assessment is created. Finally the approach for assessing urban ecosystem health, including index system, index weight, assessment standard and assessment model, is brought forward. (5) Assessment of Guangzhou ecosystem health The practice of assessing urban ecosystem health is fulfilled with case study in Guangzhou. The result shows that, Guangzhou ecosystem lies at down-healthy level, and the bad factors are mainly the resilience of ecosystem and public health. By predicting the situation of Guangzhou ecosystem after implementing management measures, we are sure that Guangzhou is going to be very healthy in 2020. The result tallies with the real situation, and it can provide the credible background and foundation to Guangzhou's ecological planning. The practice suggests that the theory and approach for assessing urban ecosystem health given by this thesis is feasible.