In 1897, all native beavers (Castor canadensis) in North Carolina were gone; hunted and trapped to local extinction. In 1939, the N.C. Department of Conservation and Development got 39 beavers from Pennsylvania and released them in the Sandhills area. In 1979, after reporting on several incidents of beavers blocking drainage canals in eastern North Carolina, I wrote a column for the small daily newspaper I worked for suggesting that this was Mother Nature’s revenge for the water quality, water chemistry, and habitat damage done by artificial drainage ditches and canals in the region (it was not well received by the local agribusiness and land development establishment). By the early 1990s, scientific articles were appearing about the recovery of beaver populations in the southeastern U.S. (1).
The story in South Carolina is similar—gone due to trapping and hunting by the end of the 1800s. The U.S. Fish and Wildlife Service reintroduced beavers in S.C.’s Pee Dee region in 1940. Around the same time, Georgia beavers began to recolonize the Savannah River drainage along the GA/SC border. Both populations expanded their range, according to the S.C. Department of Natural Resources, moving toward each other. Beavers are now found in all 46 S.C. counties.
Beavers are iconic in several ways in my corners of the scientific world. Through their dam building and pond construction, they are the prototype (other than Homo sapiens, of course) ecosystem engineer—0rganisms that modify the environment to suit their own needs and affect resources and habitats for other organisms as well. They are also a prototype for the concept of the extended phenotype. An organism’s genotype is its genetic makeup, and its phenotype is how the genes are expressed in its physiology. The extended phenotype is in essence how its genes are expressed in the external environment. Beavers are also prominent in recent and ongoing efforts to use nature-based solutions in stream and wetland restoration.
Beavers are a significant part of swamp fauna, but though their impacts are known to be significant, we don’t know a whole lot. The Classification of the Natural Communities of North Carolina (2), in the section on coastal plain floodplain forests, states:
The most poorly known natural dynamic process of floodplains is that of beavers. Beavers can dam small stream channels or may impound tributary streams or sloughs within large floodplains. Beaver ponds can raise the local water table beyond the extent of standing water. A beaver dam on an outlet slough (gut) through a natural levee can impound a large area of a complex pattern determined by microtopography. Beavers have been returning to North Carolina for several decades, after a much longer absence . . . . Little is known about their natural population dynamics, predation, disease, nor about past pond longevity and return intervals. An important question for small streams is whether all parts of a stream are suitable for pond building, so that beaver ponds appear randomly and eventually affect the whole area, or if certain favored sites are chronically ponded while others never are. In large river floodplains, only specific sites can be flooded by beaver dams; the natural levees, high ridges, and some backswamps and sloughs are not susceptible (p. 600).
Answering those questions is a tall order. Many beaver ponds in swamps are remote; you could not access them in anything other than a canoe or kayak or waders. Remote sensing experts can detect beaver dams and ponds from imagery, as a 1996 study on the Roanoke River, NC did (3). However, I looked at Google EarthTM images that spanned a period on Otter Creek in Craven County, NC before, during, and after the appearance and disappearance of a beaver dam and pond (in an area near my home where I paddle several times a year). I could not detect the emergence, presence, or loss of the feature from the images due to the complex pattern of flooding that occurs independently of any beaver ponds.
Beaver dam and pond on upper Otter Creek, a tributary of the Neuse River estuary, The dam was not present in early 2017, and present by March, 2020. It was still there in 2022, and gone by late 2024. It is not known if the pond was abandoned, washed out by a flood, or removed by property owners.
The classification (2) includes at least 14 different descriptions of ecological, hydrological, geomorphological, and soil transitions associated with either the establishment or drainage/abandonment of beaver ponds in the N.C. Coastal Plain alone (more are described in the Piedmont and Mountain provinces).
A 2015 study of sediment trapping in beaver ponds included 4 coastal plain sites in Pitt County, NC and coastal plain sites in Virginia (4). On the coastal plain, they estimated that one pond per kilometer of stream length would result in 19 million cubic meters a year of deposition in the VA and NC coastal plains. They also noted that when beaver ponds are constructed on artificially channelized streams, they often restore the natural hydrological and ecological functions of the floodplain by reconnecting the channel and floodplain.
Dam on a slough of the Black River in Bladen County, NC.
I think it likely that beavers are responsible for some of what I call water savannas or water woodland; permanently flooded floodplain depressions with mostly or entirely large, older bald cypress (Taxodium distichum) and tupelo (Nyssa biflora; N. aquatica) trees. Construction of a beaver dam floods a section of floodplain forest, and most of the trees die off (or are chewed up by beavers). Mature tupelo and cypress, however, can survive constant inundation, and while not excluded from an occasional beaver chomp (see below) are not favored. In the lower coastal plain settings where I’ve observed the water savannas, sediment inputs are very low, and abandoned beaver ponds fill in only very slowly, if at all. Tupelo and cypress remain in the ponded floodplain. This is just my proposed story, mind you, but it is plausible and fits the evidence of many of my field observations.
A selection of water savannas & woodlands in the lower Neuse River drainage basin.
Beavers are not believed to chew on bald cypress, and I had rarely seen evidence of it before, but on Core Creek near Cove City, NC in January there was extensive evidence of chewing on cypress knees.
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(1) Butler, D.R. 1991. The reintroduction of the beaver into the South. Southeastern Geographer 31, 39-43.
(2) Shafale, M. 2023. Classification of the Natural Communities of North Carolina. Fourth Approximation. Raleigh: N.C. Natural Heritage Program.
(3) Townsend, P.A., Butler, D.R. 1996. Patterns of landscape use by beaver on the lower Roanoke River floodplain, North Carolina. Physical Geography 17, 253-269.
(4) Kroes, D.E., Bason, C.W. 2015. Sediment-trapping by beaver ponds in streams of the mid-Atlantic Piedmont and Coastal Plain, USA. Southeastern Naturalist 14, 577-595.
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