Author(s):
Erle C Ellis, Associate Professor* - University of Maryland - Baltimore County
Abstract:
China's densely populated rural landscapes have been transformed over the past fifty years by population growth, social restructuring and technological change. The global environmental impacts of these changes are undoubtedly significant, yet investigation of their causes and consequences remains a challenge because they are meditated by hundreds of millions of rural households acting locally across an area of more than 2 million square kilometers. Using a regional sampling and upscaling design, we integrated high-resolution landscape change measurements, soil and vegetation sampling, household surveys and elder interviews at five field sites across rural China to estimate long-term ecological changes, circa 1945 to 2002, across China's densely populated agricultural regions. These methods revealed net increases in impervious surface area caused by housing construction that are similar in magnitude to the total current extent of China's cities. More surprisingly, these changes were associated with net increases in woody vegetation and tree cover caused by tree planting and regrowth around new buildings, the introduction of perennial agriculture and improved forestry, and the abandonment of annual crop cultivation. These observations demonstrate that fine-scale changes within anthropogenic landscapes can contribute substantially and in unforeseen ways to global changes in biogeochemistry, biodiversity and climate. Sampling and upscaling methodologies that facilitate the coupling of local observations with regional data and models therefore play a critical role in efforts to assess and mediate the regional and global impacts of land use changes in densely populated landscapes.
