IntroductionLong-term environmental changes in urban ecosystems in the United States such as habitat loss and fragmentation, drastic modifications of local and regional climate, and contamination and depletion of water resources have raised concerns among researchers across many disciplines, such as ecology, geography, anthropology, sociology, planning, and design. Certain disciplines, such as landscape architecture, urban planning, and urban design, can help determine how policies, plans, designs, and management strategies respond to the long-term environmental changes in urban environments. New research initiatives in urban and regional ecology in the United States represent an unprecedented opportunity for a broader dialogue between ecologists, social scientists, planners, and designers about the future of cities worldwide. However, the integration of ecological research into urban policy, planning, design, and management strategies is complex, but it is one of the key issues and research priorities in landscape ecology (Musacchio and Wu, 2002;Wu and Hobbs, 2002). In order to address this challenge, ecologists, social scientists, planners, and designers will need to work collaboratively to develop interdisciplinary approaches for understanding the effects of long-term changes in urban spatial patterns, landscapes, and environmental quality. Landscape architects, urban planners, and urban designers will need to be able to utilize such interdisciplinary information in the development of sustainable human settlements.In the United States, important examples of interdisciplinary approaches are occurring at emerging centers of urban ecological research and application such as Baltimore (MD), Detroit (MI), Phoenix (AZ), Seattle (WA), and Willamette Valley (OR). These groups are performing large-scale ecological studies of urbanized and urbanizing regions and are funded by recent initiatives of the National Science Foundation (e.g., Long-Term Ecological Research and Biocomplexity), Environmental Protection Agency (e.g., Science To Achieve Results), NASA (e.g., Land Use and Land Cover Change research), United States Geological Survey, and United States Department of Agriculture. The researchers include ecologists, geologists, social scientists, planners, and designers who investigate how ecological research 176 MUSACCHIO AND WU about changing urban environments can be integrated into policy, planning, design, and management strategies. Despite these significant efforts, we have only begun the process of developing a comprehensive knowledge base for building more sustainable cities and regions.This special issue highlights some of the important contributions from these studies, together representing one of the current frontiers in ecology: interdisciplinary studies of changes in human-dominated landscapes and their ecological and socioeconomic consequences. The special issue provides insights into the status of research and applications from the leading centers of urban and regional ecological research in the United S...