长江流域生态系统格局演变及驱动力

长江流域生态系统格局复杂,多种社会经济、政策和自然因素对土地利用变化的影响使得生态环境发生变化。分析了2000年至2015年长江流域生态系统格局和演变特征,及主要驱动力对生态系统变化的贡献。15年间,共有约6.4万km~2的生态系统类型发生变化,城镇增长67.5%,农田缩减7.5%,森林增加2.1%,剧烈的生态系统变化集中于下游,以及中上游的大城市,城镇聚集区以及退耕还林区。生态系统景观破碎化程度和景观多样性提高。上、中、下游生态系统格局、构成差异较大,15年间,上游和下游森林显著增加,下游城镇显著扩张、农田和湿地显著缩减,上游湿地增加最为显著。城镇化是生态系统格局演变的首要驱动力,对生态系统变化的贡献率达48.0%,长江下游城镇化的贡献率高达64.5%。生态保护与恢复工程是第二驱动力,对生态系统变化的贡献率为32.8%,在上游高达47.8%。水资源开发和农业开发贡献率分别为8.5%和9.9%,此外,气候变化促使高原湖泊面积增大。为保护长江流域生态系统的可持续发展,需划定生态保护红线,合理规划城市化进程中的土地利用,保护优质耕地,禁止重要湿地的开发。

Driving forces behind ecosystem spatial changes in the Yangtze River Basin

There are obvious differences among the upper, middle, and lower reaches in the natural environment in the Yangtze River Basin. The regional topography and climatic conditions are significantly distinct, and economic development is unbalanced. The impacts of various socioeconomic factors, policies, and natural factors on land use stimulate changes in the ecological environment. Therefore, knowledge of the ecosystem''s patterns, characteristics, and driving forces is the basis for studying the ecosystem services, ecological environmental problems, and ecological risk assessments. The ecosystem patterns, changing characteristics, and primary driving forces were analyzed from 2000 to 2015 in the Yangtze River Basin. During the 15-year period, about 6.4×10⁴ km² of the ecosystem changed, including a 67.5% increase in urban land, 2.1% increase in forest growth, and 7.5% reduction in croplands. These dramatic changes were concentrated in the lower reaches, big cities in the upper and the middle reaches, urban agglomerations, and reforested cropland areas. Ecosystem patterns and compositions in the upper, middle, and lower reaches were different. Forests and wetlands in the upper reach and urban land in the lower reach increased significantly, whereas croplands and wetlands in the lower reach decreased substantially. Through the analysis of landscape patterns, the degree of landscape fragmentation, as well as landscape diversity, increased. Between the years 2000 and 2015, the change in ecosystem patterns in the Yangtze River Basin was influenced by urbanization, ecological conservation and restoration, water resource development, agricultural development, geological hazards, and climate change. The contributions of the primary driving forces to ecosystem changes varied for the upper, middle, and lower reaches. The first important driving force was urbanization, with a contribution rate of 48.0% and up to 64.5% in the lower reach. The second important driving force was ecological conservation projects, with a contribution rate of 32.8% and up to 47.8% in the upper reach. Water resource development and agricultural development contributed 8.5% and 9.9%, respectively. In addition, the area of plateau lakes increased due to climate change. To sustainably protect the ecosystem in the Yangtze River Basin, the design of the ecological conservation redlines, reasonable land use planning in urbanization, conservation of high quality cropland, and the prohibition of development on important wetlands are necessary.