Nantucket’s sandplain grasslands and coastal heathlands are upland plant communities unique to this region of North America. Once common along the northeastern seaboard, residential and commercial development and succession to shrublands has all but eliminated these habitats from other coastal areas from Long Island, New York to coastal Maine. It is currently estimated that between 85-98% of the worldwide acreage of these habitats have been lost since the 1850’s, with the vast majority of remaining sites occurring on Nantucket, Tuckernuck, and Martha’s Vineyard.
Sandplain grasslands are relatively flat, open habitats similar to the prairies found in the Midwest. They are generally found on the southern portion of the island, geologically known as the outwash plain, where fine sand and debris were deposited by glacial meltwaters. As the name implies, this habitat is dominated by grasses, interspersed with annual and perennial wildflowers such as false indigo, bluets, field pussytoes, pearly everlasting, trailing arbutus, yarrow and many species of asters and goldenrods. Patches of low-growing shrubs occur among the grasses and wildflowers.
Coastal heathlands, or “moors,” as they are locally called, contain many of the same plants as sandplain grasslands. However, heathlands contain larger patches of shrubs, including black huckleberry, lowbush blueberry, bayberry and pasture rose with some grasses interspersed. They are located primarily in the central and northern portions of the island, where the glacier reached its southern-most extent and deposited large quantities of course sand and rock. Low ground cover plants such as bearberry, alpine reindeer moss, and false heather are adapted to growing on these nutrient-poor, gravelly soils.
Both of these habitats are the product of extensive human use. It is believed that the early Native American settlers burned large plots of land for agricultural use and to stimulate the production of native berries. Later, European immigrants that arrived in the mid-1600’s brought large numbers of grazing animals with them; by 1845 there were approximately 15,000 sheep grazing on Nantucket. The sheep overgrazed the woody vegetation, allowing low-growing heathland and grassland plants to develop without competition for sunlight and nutrients. Grasslands and heathlands that occur in close proximity to the coast were, and still are, somewhat maintained by the constant impact of salt spray.
The grasslands and heathlands created by fire, grazing and other human activities now support high concentrations of rare and endangered animals and plants. Low, grassy vegetation provides the rare northern harrier (formerly called marsh hawk) with ideal conditions for hunting their primary prey species, the meadow vole. Although populations of this species across the northeast are declining as large, contiguous areas of nesting and hunting habitat are permanently lost to development, they appear to be somewhat stable here on Nantucket. New England blazing star, lion’s foot, eastern silvery aster, sandplain blue-eyed grass, broom crowberry and sandplain flax are examples of some of the rare and endangered plant species that are found in Nantucket’s grasslands and heathlands. These wildflowers, grasses and shrubs thrive on the nutrient-poor soils that are common on Nantucket.
The change in plant species composition over time in a natural community is known as vegetative succession. This natural process has resulted in the loss of many of Nantucket’s grasslands and heathlands. Whaling sharply declined in the late 1860’s, causing many residents to leave the island in search of work. Sheep grazing became less common and eventually nonexistent. Over the last century, the lack of grazing pressure and a decline in the amount of natural and human-induced fires has allowed shrub species to grow and out-compete rare grassland and heathland plants. If left unchecked, Nantucket’s rare plant communities will eventually be replaced by scrub oak and pitch pine and their associated rare species will eventually disappear due to lack of suitable habitat.
Because these two habitats are largely the products of human land use practices, active management is needed to prevent them from disappearing. The Foundation played a leadership role in the formation of the Sandplain Grassland Network and continues to work with project collaborators to develop collaborative research and management methods aimed at slowing or reversing the encroachment of woody vegetation into these habitats and maintaining rare species. Prescribed burning, mechanical brushcutting, disk harrowing and targeted sheep grazing are all techniques that have been tested on Foundation-owned properties. While these strategies may initially seem destructive, research has shown that they are effective in maintaining rare grasslands and heathland plant communities and providing habitat for their associated wildlife.