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Plantation Blues
Trees damaged by Hurricane Bob in 1991. |
In the tropics, commercial interests are disrupting the ecological balance and decimating the native diversity of species by destroying rainforest. Several thousand miles north, on the Massachusetts island of Martha's Vineyard, a forest-growing venture threatens similar effects on a smaller scale. While environmentalists attempt to protect the tropics from further human incursions, preserving biodiversity on the Vineyard may involve destruction, according to David R. Foster, director of the Harvard Forest, and Glenn Motzkin, research assistant in plant ecology. Their recent paper on the Manuel F. Correllus State Forest, a 5,200-acre site at the heart of the Vineyard, recommends destroying 1,200 acres of conifer forest by cutting, girdling, or burning the trees. Environmentalists are applauding.
The Correllus Forest is a sand plain, a flat landscape composed entirely of sand outwash from the glacial melt of the last Ice Age. Although Long Island, Nantucket, and Cape Cod also have sand plains, Foster calls them an "extremely rare environment, in North America and worldwide." The Vineyard study is part of an ongoing project on coastal landscapes that are threatened by development in the Northeast; Foster and Motzkin used field work and archival information to understand the prehistoric and historic record of the forest now growing amid a popular summer-vacation resort.
Long before the bikini-and-barbecue crowd arrived, the Wampanoag Indians inhabited the Vineyard, subsisting largely on marine resources. Then came the Europeans, who, at the height of their farming in the early nineteenth century, had cleared and fenced virtually all of the island's coastal lowlands and adjacent morainal hills for crops and livestock. But the sand plain at the center remained unoccupied. "Lonely, wind-swept, and haunted by swooping hawks...the Great Plain has always been looked upon as a waste place," wrote the Vineyard Gazette in 1930. If its drought-prone soils, lack of surface water, and constant threat of fire discouraged human occupancy, so did the forbidding cover it supported: a thick, tangled, stunted woodland dominated by scrub-oak, overtopped here and there by black, white, and regionally scarce post oaks, with patches of pitch pine. Paleoecological evidence suggests that this native plant community has held sway there for at least the last millennium--and has survived, structurally intact, through the wildfires and fuelwood-cutting of the human-settlement period.
In 1908 Massachusetts established a 612-acre reservation on the "wasteland" plain in a vain attempt to save the last remnant population of the heath hen, the eastern subspecies of the greater prairie chicken. What soon became a state forest developed a life of its own, and grew to more than 4,000 acres by the time the last heath hen expired in 1932. By then the state had begun a long-running project of planting large and small conifer stands--chiefly red, Scotch, and white pines and white spruce, all foreign to the island--plus even more exotic species such as Spanish, Austrian, Japanese black, and ponderosa pines. The goal was to establish a lumber industry to boost the island's economy.
Young vigorous white pines above understories of native shrub species. As these planted trees mature, their dense shade may reduce or eliminate understory species that provide a habitat for rare insects. |
When the last large conifer plantings were completed in the mid 1960s, fully a third of the Correllus State Forest was in pine-spruce plantation. In the ensuing decades, the fungal pathogen Diplodia pinea wreaked havoc in the red pine stands. Hurricane Bob paid a visit in 1991, further reducing the arboreal acreage, and by then the whole experiment had become the target of widespread second-guessing. Foster and Motzkin found that several factors--soft local demand for timber, tree-damaging pathogens, windthrow destruction during winter nor'easters, and thrice-a-century major hurricanes that batter the Vineyard--prevented the tree plantations from earning money for either the island or the state. Nor were they likely to do so. Pathogen-killed and windthrown conifers loaded the forest with combustible fuel, increasing the danger of runaway forest fires like the pair of blazes in the spring of 1927 that scorched 6,400 acres apiece between West Tisbury and Edgartown. Furthermore, mature conifer stands have begun to shade out the native vegetation, endangering fauna such as the rare barrens imperial moth and coastal barrens buckmoth, which inhabit scrub-oak-protected cold depressions called frost bottoms.
Foster and Motzkin recommend dismantling the conifer plantations. The early response--official and lay, on-island and off--has been almost entirely positive. The enormous job could be undertaken piecemeal, starting with the younger stands and eventually tackling mature plantings--or, the study suggests, perhaps as a single project in the form of a liquidation sale. Could an offshore softwood sale actually attract bids? "I think it's potentially viable," Foster says. "There's an awful lot of timber on those 1,200 acres. A big outfit could bring a barge over and work through the winter with low-impact equipment. They're moving timber a long way these days. Look at the log trucks rolling up Interstate 91, headed for mills in Canada. Why can't some outfit take timber off Martha's Vineyard?"
~ Alan Pistorius