兰州城市生态系统服务价值评估方法与结果比较

Comparison on Methods and Results of Urban Ecological System Service Value in Lanzhou City

随着城市化的推进,加之生态环境脆弱,兰州市的生态系统服务功能出现衰退,正确地评价各生态系统的服务价值对兰州市的可持续发展有重要意义。本文在Costanza等评估方法的基础上,结合生态系统的自身价值与人的主观价值评估,加入支付意愿与生态系统服务稀缺性对其进行了探索性修正。并分别运用修正前后的方法计算了兰州市2005-2009年的生态系统服务价值,对比分析了两种方法得出的动态变化情况与成因。运用Costanza等的方法得出的结果显示:兰州市生态系统总服务价值5年内上升了0.24亿元,除林地外,其余各生态系统的服务价值均呈降低趋势。运用修正后的方法得出的结果是总服务价值5年内上升了28.73亿元,林地、耕地、草地的服务价值均呈现上升趋势,林地面积的增加导致其服务价值的上升,而耕地和草地服务价值的增加是由稀缺性引起的。耕地、林地、草地是构成区域生态系统服务的主要类型。研究表明:生态系统总服务价值的升降不能反映区域土地利用是否合理以及生态系统的发展方向。两种主要生态系统稀缺性的增加是导致兰州市生态系统总服务价值上升的主要原因,这反映了兰州市土地利用的不合理性以及生态系统的退化性转变。重点保护耕地和草地资源,在城市化进程中控制城镇用地的扩张,优化土地利用结构,保障后备土地资源的数量是兰州市可持续发展的前提。

With the progress of urbanization, together with the fragile ecological environment, the ecosystem service functions of Lanzhou City have been weakened, the correct evaluation of the ecosystem service values has the vital significance to the sustainable development of Lanzhou City. Based on the evaluation method developed by Costanza et al. This paper combines the evaluations of the value of the ecological system and the human subjective value, and the exploratory corrections have been conducted based on the willingness to pay and the scarcity of ecosystem services. The service values of the eco-system of the Lanzhou City from 2005 to 2009 are calculated through using the original method and the modified method respectively. The dynamic changes and causes of the values of the ecosystem services are comparatively analyzed based on the said two methods. The results obtained via the Costanza method show that ： the total ecosystem service value of Lanzhou City has increased by RMB 24 million in five years, besides the land occupied by the forest, the values of the rest ecosystem services have decreased accordingly. The results based on the modified method show that the total service value of the ecosystem in the past five years has risen RMB 287.3 million, the service values of the woodland, farmland and grassland have also increased, the increase of the forest area has led to the rise of its service value, while the farmland and grassland service values have increased by their scarcity. The farmland, forest land and grassland are of the main types of regional ecosystem services. Research shows that： the rise and fall of the total ecosystem service values can not reflect whether the regional land use is reasonable or not, and the development direction of the ecological system. The increment of the two main types of ecosystem scarcity is the main reason that leads to the rise of the total service value of the ecosystem of Lanzhou City, which reflects the unreasonable land utilization and the degenerative change in the ecological system of Lanzhou City. Attaching great importance to the protection of cultivated land and grassland resources in the city, controlling the expansion of land use in the urbanization process, optimizing the land utilization structure, ensuring the quantity of the reserve land resources and so on are the premises of sustainable development in Lanzhou City.