We address this question through five inter-related goals: 1. Perceive long-term changes in the physical, chemical, and biological properties of lake districts 2. Understand the drivers of temporal variability in lakes and lake districts 3. Understand the interaction of spatial processes with long-term change 4. Understand the causes and predictability of rapid extensive change in ecosystems 5. Build a capacity to forecast the future ecology of lake districts We examine patterns, processes, and interactions of lakes, landscapes and people at four spatial scales: individual lakes, small drainage systems with several lakes, entire lake districts, and the Western Great Lakes region of North America. Temporally, we consider scales from a fraction of a day to decades. We use multiple approaches of long-term observation, comparison across ecosystems, experimental manipulations, and process modeling. We specifically address decadal forecasts of ecosystem change, which become the hypotheses for future long-term research. Our interdisciplinary research group includes ecologists, hydrologists, climatologists, chemists, demographers, an economist, rural sociologists, and specialists in remote sensing and information management. We expect our research to produce new conceptualizations of lake district dynamics. Among these are new insights on the dynamics and impacts of invasive species, understanding of the role of spatial location of lakes in landscape dynamics, the reflexive interactions of human and ecological processes, and the interactive effects of geomorphic setting, climate and human activity on long-term change in lake districts. The understanding of integrated landscape-lake-social systems developed through our LTER program will be useful in decisions of individuals and institutions concerned with the future of the Western Great Lakes region and the welfare of its residents. Our two field stations facilitate research in the lake districts - the Limnology Laboratory on Lake Mendota in the Yahara Lake District of southern Wisconsin and the Trout Lake Station in the Northern Highlands of Wisconsin. Our data are public and available through this web site. Most of our data sets date to 1981 when this site became one of the first 6 LTER sites funded by the U.S. National Science Foundation, but several originate as early as the 1850s or as late as the mid 1990s. We invite collaboration with others.