We study freshwater ecosystems as coupled natural-human systems. We tend to work at large spatial scales, using approaches at the interface of conservation biology and data science. Our recent work includes resource allocation problems in conservation biology, invasive species management, sustainable fisheries, and trade-offs between biodiversity and infrastructure. We use field surveys and a range of mathematical, statistical and simulation modeling approaches to address these problems, and often collaborate on the development of key GIS data sets. We focus on the Great Lakes and Great Plains, but current projects span freshwater ecosystems around the world.