Restoring an Atlantic White Cedar Bog

Albemarle/Pamlico Coastal Program in North Carolina is working with the Pocosin Lakes National Wildlife Refuge and North Carolina State University to restore an 18,000-acre (7,280-hectare) Atlantic white cedar (Chamaecypa risthyoides)/bald cypress (Taxodium distichum) bog. So far, approximately 2,000 acres (810 ha) have been replanted to primarily bald cypress and Atlantic white cedar. Plans are underway to restore wetland hydrology on the remaining acreage by installing a total of 14 water control structures on canals that drain the area. Planting of Atlantic white cedar and bald cypress will continue until the area is revegetated. The project is intended not only to benefit wildlife but also to promote water quality.

This site is of particular interest because the Atlantic white cedar ecosystem is categorized as globally endangered by The Nature Conservancv and because the area is vitally important as a water filter for the Albemarle Pamlico Estuary. Mature Atlantic white cedar bogs provide a unique habitat that has naturally acidic waters and is cooler than surrounding hardwood swamps or pinelands. Cedar bogs support high breeding bird densities (425 to 554 pairs per 100 acres or 40 ha) of species such as ovenbirds (Seiurus aurocapillus), yellowthroats (Geothlypus trichas), and prairie, prothonotary. and hooded warblers (Dendroica discolor, Protonotaria citrea, and Wilsonia citurna, respectively). Hessel's hairstreak (Mitouri hesseli), a butterfly, uses Atlantic white cedar exclusively. Black bear (Ursus americanus), river otter (Lutra canadensis), and bobcat (Felis rufus) are numerous in cedar bogs, as are the State-listed eastern diamond-back rattlesnake (Crotalus adamanteus). The federally-listed red-cockaded woodpecker (Picoides borealis) inhabits mature pond pines that are scattered around cedar bogs.

The Albemarle Pamlico system, the second largest estuary in the country, is experiencing anoxia (an absence of aquatic oxygen) and blooms of the toxic dinoflagellate Pfiesteria piscida, both of which are the result of poor water quality. Historically, the fringe marshes, creeks, and beds of submerged aquatic vegetation in the Albemarle Pamlico Estuary have provided essential nursery habitat for most commercial and recreational fish and shellfish in the North Carolina coastal area. The estuary also provides important habitat for anadromous fish, including the endangered shortnose sturgeon (Acipenser brevirostrum). All of these habitats depend on maintaining adequate water quality.

In the 1980s, the Atlantic white cedar bog was owned by a commercial operatioon that proposed to mine the area's peat and construct a large peat-to-methanol synthetic fuel plant. The proposal was later abandoned, but the area had already been cleared, ditched, and drained. The site became part of the Pocosin Lakes National Wildlife Refuge in 1990. Although the transfer of property to Federal ownership ended the threat of peat mining in the area, the site remained devoid of a natural community of plants and animals, and the water that drained from the site exceeded Noorth Carolina water quality standards for mercury. Also the nitrogen in the runoff was likely contributing to eutrophication (excess algal growth) downstream.

Peat in the project site and surrounding area (the old East Dismal Swamp) formed over the last 9,000 years since the Wisconsin period of glaciation. Vegetation deposited organic material faster than it could decompose and a thick layer of peat developed slowly over thousands of years. The peat retained the nitrogen that had been stored by growing plants and eventually created a very large bank of nitrogen. The peat also absorbed mercury from the rain water, similar to the way an activated charcoal filter cleans water by accumulating contaminants. Historically, mercury was present in the atmosphere at low levels from volcanic activity, and mercury has increased recently as a consequence of human activities (e.g., combustion of fossil fuels, smelting).

When peat bogs are ditched, the water table is lowered and the peat is aerated, which increases microbial activity and accelerates decomposition and nutrient release. To illustrate the magnitude of non-point source pollution that results from decomposition of peat, consider the following comparison. Raleigh, the capital of North Carolina, discharges 60 million gallons/day (2.26(10e6)liters) of wastewater with a concentration limit for total nitrogen of 6.0 mg/liter, resulting in a nitrogen discharge of 1,100,000 pounds/year (4.97(10e5) kilograms) . The peat on the 640-acre (260 ha) demonstration plot alone contains an amount of stored nitrogen equal to 75 years of Raleigh's waste water discharge.

Net accumulation of organic material is essential for a peat bog to perform its beneficial water quality role. If ditched bogs are allowed to decompose, they can release excess nutrient loads into coastal rivers and estuaries on par with the largest point source (e.g., industrial site) discharges. Wetlands with deep organic soils can be either very good or very bad for surface water quality, depending on their condition.

Restoration of the Atlantic white cedar ecosystem is a long-term effort. Improvements to the site's hydrology and vegetative community have already reduced mercury runoff to levels that are better than the State water quality standard. The ultimate goal is to have water leaving the site with mercury and nitrogen concentrations equal to, or less than, rainfall concentrations. Restoring the hydrology has also encouraged the growth of moss (Spagnum spp) and improved habitat for small mammals and amphibians. In 3 to 4 more years, the trees should be large enough to provide nesting sites for many neo-tropical songbirds.

Restoring hydrology and native plant communities in peat bogs can turn an environmental liability (drained decomposing peat bog polluting downstream coastal estuary) into a environmental asset (functional wetland with surface water discharges cleaner than rainwater), while improving wildlife habitat.

Mike Wicker is the USFWS Albemarle/Pamlico Coastal Ecosystems Coordinator in Raleigh, North Carolina, and Eric Hinesley is a Professor with the Department of Horticultural Science at North Carolina State University in Raleigh.

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