Emerald ash borer is approaching Minnesota’s 1 million acres of black ash wetlands. USDA Forest Service scientists at the agency's Northern Research Station and collaborators developed a framework to understand how black ash, a foundational species, affects ecosystem functions, including hydrology and food webs. They used this framework to determine how loss of black ash to emerald ash borer (EAB), a nonnative insect, and replacement with new tree species will impact these functions. Their work uses a large-scale manipulation of wetlands on the Chippewa National Forest to simulate death of black ash from EAB and to evaluate replacement tree species. A key finding is that hydrologic function is closely tied to tree cover and loss of black ash without aggressive replacement with other species leads to marsh conditions. Moreover, leaves of black ash decompose faster than other species, readily becoming food for aquatic invertebrates. Conversion to replacement trees or marsh vegetation will alter food webs and the amphibian communities that depend on them. Promising replacement trees include swamp white oak and balsam poplar. These species will maintain hydrologic function but not aquatic food webs based on black ash leaves. These findings are changing the way that black ash wetlands are managed by state and federal agencies and tribes in Minnesota and Wisconsin.