The past, present, and future of prairie potholes in the United States

S mall prairie wetlands left in the wake of retreating glaciers are commonly known as potholes. The US prairie pothole region (PPR), the area covered by late Wisconsin Pleistocene glaciation and historically dominated by tall and mixed grasslands, covers north central Iowa and western Minnesota, the area of North and South Dakota east and north of the Missouri River, and northeastern Montana. Potholes formed when ice blocks buried in glacial till melted over a period of hundreds or thousands of years and the till slumped creating a closed depression. Prairie potholes are highly productive ecosystems of unparalleled importance to breeding waterfowl and many other species of wetland wildlife. Moreover, they are important nutrient sinks, store runoff that reduces flooding, sequester carbon, and provide other environmental and socioeconomic values. Prairie potholes are also perceived to reduce agricultural land value and to impede large-scale mechanized farming. Prairie potholes are routinely classified by how long they remain ponded during the growing season, from temporary potholes (ponded for 1 to 3 weeks) to seasonal potholes (ponded for 3 weeks to 90 days) to semipermanent potholes that are usually ponded throughout the growing season and may have surface water present for many consecutive years (Stewart and …