1990-2011年三峡库区生态系统服务价值演变及驱动力

作为我国西南部重要的生态屏障和生态走廊,三峡库区具有重要的战略意义,其生态问题非常值得关注。研究以覆盖三峡库区的4期Landsat TM遥感影像为数据源,通过人机交互解译分别获得1990、1998、2006、2011年的土地利用/覆盖,参照中国陆地生态系统单位面积生态服务价值当量表,采用研究区单位面积产量与全国农田粮食单位面积产量的比值作为地区修订系数,计算库区生态系统单位面积生态服务价值当量表,同时利用生物量对林地的生态系统服务价值作进一步的修订。然后结合土地利用结构和生态敏感性指数,定量分析土地利用变化引起的生态服系统务价值变化及其驱动因子。结果显示:1990—2011年间,三峡库区生态系统服务价值主要由林地支撑(占76.75%),其次是水域、耕地(共23.19%),草地的贡献率最小(0.22%),总生态系统服务价值从1990年的479.55亿元增加到2011年的680.83亿元;各项服务功能价值中,食物生产功能价值下降,其他各项功能价值上升,以土壤形成与保护功能上升幅度最大,达36.61亿元,其次是气体调节(33.10亿元);驱动力分析表明,库区生态系统服务价值变化的主要原因是人类活动,特别是自1998年实施退耕还林工程以来,各自然生态系统的面积发生较大变化,同时,自然生态系统的健康程度和社会政策对生态系统服务价值变化的影响也不忽可视。研究表明,加强林地、草地和水域等生态系统服价值高的土地利用/覆盖类型保护,是维持库区生态系统稳定性的有效措施。

Analysis of evolution and driving force of ecosystem service values in the Three Gorges Reservoir region during 1990-2011

As the most important ecological barrier and ecological corridor in Southwestern China, the Three Gorges Reservoir region was strategically important and significant. Since the 1990s, in company with the accomplishment of the Three Gorges hydro-junction project, a series of key national ecological and forestry projects have been initiated, including the protective forests along the Yangtze River, the natural forests and Resources conservation, the conversion of cropland to forest, the afforestation of the reservoir surrounding area and the afforestation of both banks of the Yangtze River. These have led to significant changes of land use and land cover (LULC) types and their spatial distribution. More than twenty years has been gone. However, it is unknown that how the accomplishment of the ecological projects affected the change of ecosystem service values and what were the effects of these projects on the protection of the Three Gorges Reservoir region. There is a strong need to assess the effectiveness of the projects, including the dynamics of LULC types and the induced changes of ecological service values. The objective of this study was to analyze the spatiotemporal characteristics of ecological service changes and investigate the factors that have driven the dynamics in the Three Gorges Reservoir region. In this study, the Landsat Thematic Mapper^TM images that cover the Three Gorges Reservoir region were acquired for years of 1990, 1998, 2006 and 2011, respectively, and visually interpreted for LULC types. The per unit ecosystem service equivalent value of the ecosystems within the region was calculated by using the corresponding value of the terrestrial ecosystems for the whole country as a reference and the ratio of the per unit grain productivity of the study area to the corresponding value of the country as a revised coefficient. The obtained per unit ecosystem service equivalent value was further modified based on the value of biomass from forested land related to ecological service value. The changes of ecological service values induced by LULC dynamics and corresponding driving factors were quantitatively analyzed by combining land use structure index and ecological sensitivity index. The results showed that (1) during the past twenty one years, the ecological service values of the Three Gorges Reservoir region were mainly supported by the forested land with a percentage of 76.75%, followed by the water and cropland land (23.19%), and the contribution of the grassland was the least (0.22%). The total ecological service value increased from 47.96 billion yuan in 1990 to 68.08 billion yuan in 2011; (2) All the ecological service values increased except food production. The value from soil formation and protection had the greatest increase with an increment of 3.66 billion yuan, followed by the gas regulation (3.31 billion yuan); (3) The analysis of driving factors showed that the changes of the ecological service values were mainly due to human activities, especially the great change of the area for each of the natural ecosystems since the conversion of cropland to forest started in 1998. Moreover, the effects of both the health of the nature ecological systems and the social policy on the changes of the ecological service values could not be ignored. The findings implied that enhancing the protection of LULC types that have higher ecosystem service values, including forested land, grassland, water bodies and so on, is an effective way to stabilize the ecosystems of the Three Gorges Reservoir region.