The coastline is separated from the Gulf of Mexico by a shallow sound and is paralleled by a series of barrier islands. Farther inland are tracts of wet savanna habitat, home to the critically endangered nonmigratory Mississippi sandhill crane. Only small remnants are left of the formerly extensive Black Belt and Jackson Prairies, in which several species of endemic crayfish are found. Bald eagles, a threatened species, use the Upper Mississippi River valley as a winter migration corridor and for summer nesting habitat. The Mississippi flatlands in the alluvial plain attract hundreds of thousands of migrating snow geese, Canada geese, and ducks in the winter.
Wetlands play a major role in basin hydrology and serve as wildlife habitats.
Changes in water levels brought about by a changing climate can dramatically alter the extent of these ecosystems. Wet savanna habitats are already under threat from conversion into pine plantations. Coastal wetlands are among the ecosystems most vulnerable to climate change. If runoff along the Gulf Coast increases, estuarine flushing rates would increase, leading to reduced yields in shrimp and other species favoring high salinities. Increasing runoff rates and outflow into the Gulf of Mexico could increase nutrient loads and alter water temperatures, exacerbating the already serious eutrophication and low oxygen levels.