Natural Environment 7.2: Restore and Maintain Biodiversity

Biodiversity, the variety of species, is important to the health of any ecosystem, and of particular concern in some unique and vulnerable areas.  Nearly 40% of the Island (40,000 acres) has been designated by the Commonwealth as Priority Habitat for rare and endangered species of plants and animals. Several complex ecosystems form the heart of the Island’s natural environment.  

One such special area is the Sandplains, an ecosystem that is extremely rare in the world. The Sandplains are a mosaic of habitats ranging from oak and pine barrens to heathland, scrub oak frost bottoms, maritime thickets, and – perhaps the most well-known – grasslands. Sandplain Grassland is an open field community that developed on outwash plains that were created at the end of the Ice Age.  This ecosystem only developed on the outwash plains adjacent to that ice front, namely on Martha’s Vineyard, Nantucket, Cape Cod, Block Island and Long Island. The Sandplains are naturally-stressed: droughty, acidic soils, subject to frequent fire, exposed to wind and salt spray over large areas.  Even here, grasslands tend to be overtaken by shrub and forest growth in the absence of fires that historically kept the fields open, so this system is particularly vulnerable to the fire suppression that comes with human habitation.  

Overall, biodiversity is threatened by development and inappropriate management; such as habitat fragmentation, fire suppression, introduction of non-native landscapes, and the spread of invasive species.  Each particular system is more or less vulnerable to each of these impacts.

Particularly important to biodiversity is the concept of Minimum Viable Landscapes (MVL) -- the amount of ecologically functional land and surface water needed to sustain viable populations of native species. Since these areas act as essential source areas for the plant and animal inhabitants that might disperse to other parts of the Island, they are referred to as Source Areas. .

The Island Plan concluded that the area of Minimum Viable Landscape needed to maintain a viable ecosystem so that it functions as a Source Area is approximately 5,000 acres in the Sandplains and 3,000 acres in the moraines. (Naturally stressed ecosystems generally have to be larger than those with richer soils and more water.) The Plan has identified five eco-regions on Martha's Vineyard which should be protected and restored, namely: the Central Sandplain, the Coastal Sandplain, the Western (Moist) Moraine, Aquinnah, and the Eastern (Dry) Moraine (see concept map below, and Biodiversity Classification Map on next page).

The aim in these areas is not only to protect the remaining areas of native vegetation (such as the 65% of the Island that is Priority Habitat, including 25% of Estimated Habitat for rare and endangered species indentified by the Commonwealth’s Natural Heritage Program) but to use the long-term strategies described in this section to restore these areas to ecological health.  In the future, the specific assemblage of species in each of these areas might evolve as a result of climate change or other factors; however, by keeping an area of adequate size, they should be able to evolve into equally valuable natural communities.

The Biodiversity Plan uses the following tiered approach for the parts of the Island outside of town/village areas.  In general, Source Areas should be maintained and restored to large enough tracts to absorb a variety of carefully managed uses, including limited human activity (e.g. low density housing on large lots with limited development envelopes); fragmentation is of particular concern. 

Since many of the significant habitat areas are long and narrow, they are particularly vulnerable to edge effects of from adjacent developed areas, such as the intrusion of invasive plant species, non-native or hyper-abundant predators, and exterior lighting. These threats are even more problematic when it comes to the hundreds of houses located throughout the Source areas.

1.   Critical Source Habitats: These areas, such as scrub oak frost bottoms, barrier beaches, streams and valleys are individual habitats (parts of an ecosystem) that are particularly rare and vulnerable, and cannot absorb much human-based impact. These habitats tend to be linear features. Development should be avoided if at all possible.  

   2.   Source Areas – Intact: This category includes conservation lands. It also includes other areas where the habitat is still intact and where it is especially important to avoid destruction or fragmentation of habitat if possible. It is especially important that these areas are managed in their optimum native habitat as they constitute the main source of wildlife that populate the other areas (called “sink” areas).

3.   Source Areas – Lightly Settled: This category includes areas that are settled at a low enough density that native vegetation is, or could be, largely intact. Restoration and other management measures would allow these areas to harbor more wildlife.

4.   Source Areas – Heavily Settled: This category includes areas within the overall Minimum Viable Landscape of the eco-region that are largely developed and fragmented. Intense management of open spaces and mitigation of impacts from development diminish the effects on neighboring intact and lightly settled areas.  

5.   Interface Areas:  These are areas significant habitat located between the main Source Areas and the main Down-Island towns. Though they have considerable habitat value on their own, they are somewhat less critical that the more centrally located Source Areas in that they are on the edges of and are somewhat tenuously connected to the Source areas, and are in a different eco-region. The fact that they are right next to town makes them especially suitable for recreation and farming, along with habitat.

Objective N2: Protect Minimum Viable Landscapes of significant Eco-Regions to restore and maintain the conditions to protect viable populations of the Vineyard’s native species, both resident and migratory.

The Island Plan has determined how much land is needed to restore and sustain viable populations of the Vineyard’s native species. The measures discussed in the previous section can be used to protect the most significant areas as additional open space, and the following measures should be implemented to protect these important habitats.

·  Strategy N2-1: Identify and adopt performance standards for habitat protection and restoration. The Island Plan mapping of Minimal Viable Landscapes (MVL) should be refined and coordinated with other land uses, as well as with prioritized watersheds, storm-surge protection areas; overlay de-prioritized areas, e.g. those most susceptible to sea-level-rise inundation.  Local conservationists should identify essential performance standards needed from each MVL (e.g. species presence/population size, etc.) and benchmarks for measuring success; share this information with the MVC and local regulatory authorities.  Decision-makers can then use this information to promote the restoration of priority areas for habitat protection and restoration, reuniting tracts of land large enough to absorb multiple uses and still provide for biodiversity and cleaner watersheds. Town boards, planners and conservation organizations can use the mapping to locate sites for compatible land uses and can target locations where landowners would be encouraged to embrace native plant landscaping, native-grass grazing, and Undevelopment.

·  Strategy N2-2: Establish a program encouraging and facilitating Landscaping the Vineyard Way.  Replacement of native Vineyard vegetation with large, high-maintenance lawns or exotic vegetation reduces habitat, increases the need for fertilizers and pesticides that pollute our water supply, and erodes the Vineyard’s character. Some efforts have already been made to inform the public about Landscaping the Vineyard Way. A broader information campaign could help counter the effects of inappropriate landscaping techniques promoted by television advertising and by people moving here with off-Island perspectives for Vineyard landscapes.  To minimize fragmentation and watershed pollution, we should encourage the use of native grass lawns and native plant landscaping on private lands, and native plant roadside planting and management along public roads. Garden centers and landscapers could participate with a good labeling program of native species; expanded local production and sale of native Vineyard plants (as is being developed by the Polly Hill Arboretum) will also contribute to the local economy. We should create a “black list” of known invasive plant species and species known as vectors for disease, regulate against their importation, sale, and planting, and change regulations to allow the use of biocides for removal of invasive species where no practical alternative exists. An informational campaign to could help reduce the population of non-native and hyper-abundant predators (enclose compost piles and outdoor pet feeding, enclose crawl spaces under sheds and houses, reduce lawn areas, keep cats indoors, etc.). The possibility of taxing the sale of chemical fertilizers and biocides, and using the funds to promote the production of native plant stock by non-profit organizations for private, public and commercial landscaping, should be investigated.

Strategy N2-3: Increase the use of specialized management techniques such as prescribed burnings and wildlife underpasses: For thousands of years, there were periodic natural fires that played an important part in maintaining the health of the Island’s Sandplains, keeping them from being dominated by forest, as they are now. Native grasslands and many of their species do not thrive without episodic burning that has always taken place in nature.  This has been undermined by decades of fire suppression. A program of prescribed burning would involve having town Fire Chiefs and the Martha’s Vineyard Prescribed Fire Partnership prioritize sites to burn for public safety and biodiversity reasons; acclimating the public to the regular and safe use of prescribed fire through daily radio reports during burn seasons; offering annual volunteer training to assist with prescribed fire crews; and creating and maintaining a single fire cache (e.g. equipment) available for use by prescribed fire crews and Island fire departments. In some other critical areas, heavily trafficked roads divide and fragment those special lands.  One method of dealing with that fragmentation is to provide wildlife underpasses where rare or vulnerable species are unable to travel or unsafe when crossing.