Big Lake NWR was established in 1915 to provide habitat and protection for migrating and wintering birds and is recognized as an important link in the Mississippi migration corridor. Over the years the objectives of the refuge have expanded to include protection for endangered species. Big Lake was important in the recovery of the bald eagle from its endangered status. Eagles came back to nest on the refuge in 1989 and have annually raised young since 1993. Also, since most of the bottomland hardwood forests have disappeared, it has become more important to preserve and restore this habitat for the wide variety of wildlife it supports.
Once a free-flowing river system, Big Lake NWR was changed to a lake / swamp ecosystem by the New Madrid earthquakes of 1811-12. Big Lake today consists primarily of wooded swamps and open water. The lake is shallow with an average depth of three feet and is bordered by a virgin cypress-tupelo swamp with some black willow and buttonbush. Smartweed, American lotus and water lily characterize the herbaceous wetland plants. Tree species on higher ground include cottonwood, green ash, hackberry, red maple, sycamore, river birch and a variety of oaks.
Due to the fact that Big Lake NWR is an oasis of bottomland hardwood in an agriculturally developed area, 6,400 acres are designated as a National Natural Landmark and 2,100 acres of the Natural Landmark are included in the Wilderness Preservation System.
The refuge annually winters several species of waterfowl. Peak numbers in January and February can exceed 200,000. Wood ducks are year-round residents and annually raise approximately 2,500 young in natural cavities and nest boxes. Over 225 bird species have been observed on the refuge and recorded by visiting ornithologists. Other wildlife to look for are beavers, otters, raccoons, wild turkeys, white-tailed deer, bobcat and the occasional armadillo.