Ecologically, Marion is located on the border between the Northern Backswamps (west Marion) and Northern Holocene Meander Belts (east Marion) ecoregions within the larger Mississippi Alluvial Plain. The Northern Backswamps are a network of low-lying overflow areas and floodplains historically dominated by bald cypress, water tupelo, overcup oak, water hickory, and Nuttall oak forest subject to year-round or seasonal inundation. The Northern Holocene Meander Belts are the flat floodplains and former alignments of the Mississippi River, including levees, oxbow lakes, and point bars. Much of the wetlands and riverine habitat have been drained and developed for agricultural or urban land uses. The Wapanocca National Wildlife Refuge, which preserves some of the year-round flooded bald cypress forest typical of this ecoregion prior to development for row agriculture lies north of Marion.