Today, a substantial amount of marsh habitat has been destroyed by human activities. Illinois once had approximately 8.2 million acres of wetland (including marshes); today the number has been reduced to 870,000 acres with an estimated 3-5,000 acres lost per year. This is nearly a 90% loss since 1818.

Marshes are frequently destroyed intentionally (by direct bulldozing and filling of the land), but in other cases they are gradually destroyed by the development of surrounding land. The construction of roads and other infrastructure in an area reduces biodiversity and increases soil runoff. This results in a buildup of additional sediment, changes in soil chemistry, and further loss of biodiversity. Eventually, the marsh (or other wetland) dies off as human use suffocates its landscape.