Affiliation: | aDepartment of Geography and Environmental Systems, 1000 Hilltop Circle, University of Maryland, Baltimore County, Baltimore, MD 21250, United States bInstitute of Tropical and Subtropical Ecology, South China Agricultural University, Guangzhou, Guangdong 51064, China cInstitute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 10010, China dInstitute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan 410125, China eAgronomy College, Sichuan Agricultural University, Yaan, Sichuan 625014, China fDepartment of Agronomy and Agroecology, China Agricultural University, Beijing 100094, China gInstitute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210008, China |
Abstract: | Long-term ecological changes within densely populated landscapes account for a growing share of global environmental change. Measuring the causes and consequences of these changes remains a challenge because of their fine spatial scale and complexity. Here, we measure long-term ecological changes, circa 1950 to 2002, within six 1 km2 sites in densely populated rural China and in urban and suburban Baltimore, Maryland, USA using a standardized procedure for fine-scale feature-based ecological mapping from high spatial resolution (≤ 1 m) imagery. The median size of ecologically distinct landscape features (ecotopes) mapped by this procedure was just 520 m2, though size, count and perimeter of features varied considerably both within and between sites. Land management and vegetation cover changed substantially, over 28% to 87% of site areas, but most of this change occurred in small patches with area < 4000 m2. Landscape complexity also increased over time by the fragmentation of landscapes into a larger number of smaller features with an increasing diversity of ecotope classes. Detailed analysis of fine-scale landscape transformations helped identify the causes and consequences of ecologically significant changes within and across sites, including unexpected increases in perennial vegetation cover and the linkage of impervious surface area with population density. These and other results demonstrate the general utility of anthropogenic ecotope mapping as a tool for cross-site comparison and sampled regional estimates of long-term ecological changes within densely populated landscapes. |