August 1, 2022
Photo by Michael R. Jeffords.

The Coastal Plain Natural Division: Ancient Swamps Host Ecological Diversity

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By Gretchen Steele

Imagine for a moment the great southern deep-water swamps. They are filled with ancient bald cypress and water tupelo trees, whose buttresses are enormous, swollen, and large enough for a person to walk into in some cases. Trees that may well be close to 1,000 years old. “Prehistoric” aquatic species such as bowfin, gar and alligator snapping turtles make their homes in the water of these cypress swamps. Great blue herons and great and snowy egrets perch on the delicate-looking limbs of the massive bald cypress. Wood ducks, mallards and mergansers glide across the emerald-green duck weed-filled surface, adding more color and life. In the spring and summer, brilliant-colored wildflowers rise and bloom. In late spring, the songs of love-struck frogs become a cacophony of chirps, croaks and the musical bird-like song of the often heard yet seldom seen bird-voiced tree frog.

A dark and light green map of the state of Illinois with the very southern tip in white indicating the coastal plains natural division.
The Coastal Plain Natural Division is located at the very southern tip of Illinois. Illustration by Sarah Marjanovic.

Can this possibly be in Illinois? It can, and it is. The Coastal Plain Natural Division exists in Illinois’ extreme southernmost tip, encompassing most of Alexander, Pulaski and Massac counties, with small, fingerlike portions extending into Union, Jackson and Pope counties. This natural division is the far northernmost extension of the larger Gulf Coastal Plain Province of North America. This swampy, southernmost location in Illinois is mild and has the warmest climate within the state.

The coastal plain of Illinois most closely resembles lands that surround the present-day Gulf of Mexico. This natural division is divided into two distinct sections: the Cretaceous Hills Section and the Bottomlands Section. The land flattens within the Coastal Plain Natural Division, the drainage is poor, and frequent flooding occurs. Only knolls and ridges of the Cretaceous Hills break the broad plain of alluvium from the Cache, Ohio and Mississippi river bottoms that make up this natural division.

Because the natural division shares borders with the Ozark, Lower Mississippi River Bottomlands and the Shawnee Hills natural divisions, it supports incredible ecological diversity. Four Physiographic Provinces (regions which are similar in geologic structure and climate, and which have had a unified geologic history) converge in southernmost Illinois—the Coastal Plain, Interior Low Plateaus, Ozark Plateaus, and Central Lowland. The natural communities found in the Coastal Plain Natural Division are home to more than 100 threatened or endangered species of flora and fauna.

Water tupelo trees in a swamp with trunks speckled light green with lichen.
Water tupelo trees in a swamp. Photo by Michael R. Jeffords.

The Cretaceous Hills Section of the Coastal Plain Natural Division is a narrow band from the Mississippi River to the Ohio River. It consists of low hills made of gravel, sand, and clay remnants of the Cretaceous deposits found in Kentucky and Tennessee. These low hills are home to multiple seep springs. Interestingly enough, plants usually associated with bogs are found in this section, including sphagnum moss and a fantastic array of ferns.

The Bottomlands Section contains southern swamps of bald cypress and water tupelo at their northernmost limits. A thick green blanket of duckweed often surrounds the trees. Mark Guetersloh, Illinois Department of Natural Resources (IDNR) heritage biologist for the region, succinctly explained the difference between the two divisions. “Think upland forest and seep springs in the Cretaceous Hills. Conversely, the Bottomlands Section is a place of alluvial soils, floodplain forests and swamp forests.”

The ecological diversity and importance of the Coastal Plain Natural Division should not be understated. There are 63 Illinois Natural Areas Inventory Sites in the Cache River Basin totaling 18,444 acres, 52.8 miles of Biologically Significant Streams, 298 Natural Heritage Sites and 8 Nature Preserves. Multiple areas exist under varying degrees of management, including two National Landmarks—Buttonland Swamp and Heron Pond.

Two yellow birds with gray wings and tails perch on a tree branch over a duckweed covered swamp.
Courting prothonotary warblers on Cache River. Photo by Michael R. Jeffords.

Other sites of note where visitors can get a good look at and feel for the incredible diversity of the Coastal Plain Natural Division include: IDNR’s Section 8 Woods, Heron Pond-Wildcat Bluff, Little Black Slough, and the Cache River State Natural Area. Additionally, U.S. Fish and Wildlife Service (USFWS) maintains the Cypress Creek National Wildlife Refuge.

Historically the area suffered greatly at the hands of man, beginning with the first settlers in the early 1800s who focused on timber harvesting. In the early 1900s, the focus switched to developing the land for agricultural use resulting in large-scale drainage and land clearing efforts.

Today, thanks to the cooperative efforts of the Cache River Wetlands Joint Venture Partnership (JVP), the focus is to repair natural ecosystems and provide a variety of both consumptive and non-consumptive recreational uses. The partnership guides management in a way that offers a balance of promotion, tourism, and economic development while preserving and conserving the rich natural resources unique to this Natural Division.

This particular partnership and cooperative effort are unique, according to Guetorslough. “Nowhere have I seen so many…unite to accomplish so much than the Cache River Wetlands JVP. This project includes the USFWS-Cypress Creek National Wildlife Refuge, IDNR, The Nature Conservancy, Ducks Unlimited and the USDA-Natural Resources Conservation Service. Other players that have worked with the JVP included the Illinois State Water Survey, Friends of the Cache River Watershed, U.S. Army Corps of Engineers, Illinois Audubon Society, Shawnee Audubon Chapter of Illinois Audubon Society, Sierra Club, Citizen’s Committee to Save the Cache River, Little River Research and Design, Southern Illinois University-Carbondale, Shawnee College and many other individuals, organizations and groups.”

A brown and tan snake swims in a swamp.
Swimming cottonmouth. Photo by Michael R Jeffords.

While the ancient cypress swamps could be considered the “signature” natural community for the Coastal Plain Natural Division, one would almost have to consider birds the signature inhabitants. The list of bird species found there is magnified by its place in the seasonal migratory paths. Spring and fall migration periods bring multitudes of waterfowl, warblers and shorebirds to the area.

Other wildlife frequently found in the natural division include white-tailed deer, gray and red foxes, beavers and mink.

Observers of aquatic species are certainly not disappointed by the array of fish, amphibians and reptiles. Pygmy sunfish and cypress minnows are two state-endangered fish found only in the forested swamps. Three well-known venomous residents inhabit the area: the cottonmouth, copperhead and Illinois-threatened timber rattlesnake.

Those intrigued and wishing to visit this incredibly unique and diverse natural division are encouraged to begin their exploration at the Barkhausen Wetlands Center. There a vast amount of information, displays, and outdoor-related activities help visitors understand and begin their exploration of the numerous publicly accessible recreational opportunities within the Cache River Watershed and the Coastal Plain Natural Division. Visitors can easily choose whether to traverse the area via kayak or canoe, on foot, on bicycle or car. If time is short, a visit to Heron Pond will offer visitors a close look at the true nature of the primordial swamp via a well-maintained trail and floating boardwalk. The boardwalk allows visitors to immerse themselves in the cypress swamp and its diverse inhabitants.

Whether you have only a single day to visit or want to plan a more extended stay, the Friends of the Cache website can be most helpful for those planning a trip to this rich and diverse area.


Gretchen Steele hails from Coulterville, Illinois. Steele is a freelance outdoor communicator. Her award-winning work appears as a regular columnist and contributing feature writer for Heartland Outdoors, Illinois Outdoor News and several Illinois newspapers. She enjoys spending her time afield as a volunteer for the Illinois Department of Natural Resources, Delta Waterfowl Foundation, Retrievers Unlimited and the Illinois Federation of Outdoor Resources. She is currently Vice President of Missouri Outdoor Communicators and a former board member of Association of Great Lakes Outdoor Writers.

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