一种城市生态系统现状评价方法及其应用

生态城市建设是未来城市发展的最终趋势。从结构、功能、活动、发展演化规律等方面来看,城市生态系统都可以被看作一个动态变化的系统。将可持续发展理论引入到城市生态系统现状评价中,提出和解释了城市生态系统可持续发展概念;从可持续发展的角度,评价城市生态系统的现状,建立城市生态系统可持续发展评价指标体系。在此基础上,利用集对分析方法,将评价城市生态系统可持续发展水平的多个指标系统合成一个与最优评价集的相对贴近度,用来描述城市生态系统可持续发展水平,并将该方法应用于兰州市城市生态系统现状评价。结果表明,在2004—2010年间,兰州市城市生态系统可持续发展水平呈现折线型关系,而且有明显的陡降现象。具体变化趋势是从2004年的0.5081平缓上升到2005年的0.5581、然后陡降到2006年的0.4073、接着平缓上升直到2009年的0.5010、最后平缓下降到2010年的0.4706。尽管不同时期城市生态系统可持续发展水平有所变化,但是总体来说,一直处在基本可持续发展的水平,协调程度一般;该评价方法能够很好的反映城市生态系统的发展现状,为建设生态城市提供科学依据。

An urban ecosystem assessment method and its application

The concept of an eco-city is the ultimate trend for future cities. Supported by the principles of ecology and sustainable development theory, an eco-city is a sustainable urban area developed and designed to create a regional natural city environment. An eco-city is an artificial ecosystem featuring a clean and desirable environment compatible with continuous economic improvement. An eco-city is beneficial to human health, prosperity, social harmony and progress, and it allows for expanding opportunities and is full of complexity. Urbanization continues to increase along with the development of human society, civilization and the economy. Prosperity also brings ecological and environmental problems to cities, such as climate change, pollution, energy shortages, ecological damage and the disruption and destruction of local communities, all of which seriously threaten the health of urban ecosystems. In general, people have started to look at cities from the perspective of maintaining a balance between ecological integrity and sustainable development. The construction of eco-cities has gradually become a global focus point. Urban ecological systems are complex with natural, economic and social subsystems. The primary functions of urban ecosystems are to provide the human residents with satisfactory and productive lives, and with entertainment and local transportation. The characteristics of urban ecosystems are: 1) they are mainly artificial man-made ecosystems, 2) they are incomplete ecosystems, and 3) there is an obvious flow of human harnessed energy in urban ecosystems. The structure and characteristics of urban ecosystems determine their basic function. Because urban ecosystems are similar to natural ecosystems, urban ecosystems have the functions of production, energy flow, material cycling, and information transmission. Because urban production includes economic and biological production, and economic production includes the city's main social processes, the basic functions of urban ecosystems are much more complex than those of natural ecosystems. Urban ecosystems achieve their basic functions through energy flow and material cycling. It is easy to see that urban ecosystems are dynamic based on aspects of the structure, function, activities, and the evolution of urban ecosystems. This paper introduces the concept of sustainable development theory and explains how this theory can be used to assess urban ecosystems and explains the concept of urban ecosystem sustainable development. Urban ecosystems are assessed from the viewpoint and concept of sustainable development and an indicator system is established based on this concept. The Set Pair Analysis Method (SPAM) is used to assess the level of sustainable development in urban ecosystems. SPAM can be used to combine multiple sustainable development indices to optimize a finely tuned degree of sustainable development. The application of this method in Lanzhou City, Gansu Province shows that during 20042010, the level of sustainable development in this urban ecosystem fluctuated and sometimes obviously declined. The overall trend of change gently rose from 0.5081 in 2004 to 0.5581 in 2005, declined rapidly to 0.4073 in 2006, rose uniformly and slowly to 0.5010 until 2009, and then declined to 0.4706 in 2010. Despite these changes in sustainable development over time in this urban ecosystem, the overall level of sustainable development slowly increased. Also, the assessment results indicate this method can easily reflect changes to the development of sustainable urban ecosystems, and can provide a scientific basis for the construction of an eco-city.