Wetlands are powerful ecosystems that help clean water, reduce flooding, and store carbon. But in many parts of North America, millions of wetlands have been drained over the past century for farming and development. While today's science and policy often focus only on wetlands that still exist, we may be overlooking a huge piece of the puzzle. In this talk, I’ll share new research that maps these “lost” or drained wetlands across the Upper Mississippi River Basin and the U.S.–Canada Prairie Pothole Region. Using satellite data, historical maps, and advanced computer models, we’ve built a dataset showing where wetlands once were—and how those locations still matter today. Even after wetlands are drained, the land often behaves differently, affecting how water flows and how crops grow. By better understanding where wetlands used to be, and what they still influence, we can find new opportunities for restoration that support cleaner water and a more climate-resilient future.