America's Wetland: An Environmental and Cultural History of Tidewater Virginia and North Carolina

13. From Peat Mining to Wildlife Refuges

177 13 From Peat Mining to Wildlife Refuges The Albemarle region of southeastern Virginia and northeastern North Carolina holds some of the largest deposits of peat in temperate North America, comparable in area to that in Ireland. The Albemarle peninsula in particular ‘‘has the largest and deepest peat soils in North Carolina’’ and contains nearly half the peat for the entire state. Similarly, the Great Dismal Swamp north of the Albemarle Sound also has rich deposits. In both regions the depth of the peat generally ranges from one to seven feet, but it can be up to fifteen feet, or more, in certain areas.∞ These pocosin peatlands are unique and constitute a once-living record of plant life here thousands of years ago. Partially decomposed leaves, twigs, tree trunks, and stumps have all been preserved under the anaerobic conditions of swamp water. Peat is the geological predecessor of coal, and like coal, the fundamental element is basically carbon that was removed from the atmosphere by photosynthesis long ago. In other words, over geologic time plants in these wetlands removed significant quantities of carbon dioxide from the atmosphere and stored it as peat for thousands of years. In modern jargon, the Albemarle peninsula is an environmentally valuable ‘‘carbon sink,’’ perhaps the largest in the eastern United States. The age of these peat deposits is relatively young, coinciding with the rise of sea level associated with the end of the last ice age. In the Albemarle peninsula, for example, the average age of the peat was radiocarbon dated at 4,500 years (range 1,715 to 8,895 years). These pocosins have produced 178 W America’s Wetland on the order of 535 pounds of carbon per acre each year throughout this period (0.06 kg per square meter per year), roughly about 10 percent of their annual photosynthesis. The richest form of peat in these pocosins contains up to 60 percent carbon. By way of caveat, however, this invaluable carbon sink is strictly dependent on the peat staying submerged in stagnant water such that oxidation does not occur. Humanity’s disturbance of this region, especially by land drainage, has released great quantities of carbon into the atmosphere and led to land subsidence and release of toxic chemicals such as mercury. Peat Oxidation: Land Subsidence Under certain conditions water can be a superb preservative. The key is the absence of oxygen, an element necessary for life, as well as the absence of microorganisms that normally decompose organic (carbonbased ) material. Stagnant water of tidewater swamps is typically anaerobic , that is, all the dissolved oxygen has been used up. Thus, leaves, limbs, and trees that fall into such water are barely oxidized. Other factors are at work, of course, but one can generalize that the spongy organic soil (peat) underlying these massive swamps is attributable foremost to being submerged in standing water for thousands of years. When this water is removed, either naturally via droughts or by humans for land drainage, great quantities of (unoxidized) organic material are exposed to oxygen, a highly reactive element. This material will then inevitably oxidize (‘‘burn’’). This oxidation process may be slow, whereby the organic components of the soil will gradually return to carbon dioxide, or related oxide gases (methane is not an oxidation product), and eventually ‘‘disappear’’ (subsidence). Alternatively, it may oxidize quickly in the form of fire. Either way human activity has tipped the balance, and peat is quickly disappearing from these wetlands, releasing large quantities of ‘‘greenhouse gases’’ into the atmosphere. The entire process can be reversed if the water table is raised to original levels (i.e., if land drainage is stopped). When swampland is cleared for cultivation, and subsequently drained, a barely perceptible process commences within organic soil (peat) that does not occur in mineral soil. Organic soil, affectionately called ‘‘black gold’’ by farmers, literally disappears over time. This soil subsidence was From Peat Mining to Wildlife Refuges W 179 observed at Somerset Place at Lake Phelps as early as 1839 by the pioneering agronomist Edmund Ruffin of Petersburg, Virginia (see chapter 11). In the process of clearing land here, trees were killed by ringing and left in place for up to several decades. These trees and stumps constituted a marker by which the soil level could be measured over many years, as one account concluded: ‘‘In the land cultivated this year [1839] for the first time, though drained...