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Reading Room - Watershed Perspectives - Bio-diversity

Protecting Biodiversity in the Nashua River Watershed
by Heidi Roddis, Senior Policy Specialist, Massachusetts Audubon Society

Biodiversity is a term that we often hear in relation to global environmental issues such as the loss of tropical rainforests. But biodiversity is also something that we need to be concerned about right here in the Nashua River watershed and our own backyards. Within this local section of the Massachusetts landscape are many different kinds of natural communities, from rivers, ponds, and lakes, to red maple swamps and riverine marshes, to mixed hardwood forests, to subalpine red spruce stands near the summit of Wachusett Mountain. The Nashua River watershed is located on the boundary between two ecoregions: Worcester-Monadnock Plateau and the Southern New England Coastal Plains and Hills. Because it straddles two ecoregions, the Nashua basin harbors more biodiversity than a geographic area confined entirely to a single ecoregion.

What is Biodiversity?
Biodiversity, or biological diversity, refers to the enormous variety of species and genetic variety within a species, as well as diversity at the ecosystem level and the natural processes that maintain ecosystem function. Some habitat types and species that live within them are common and widespread in the Nashua basin, while others are rare. Some species require a combination of habitats for their overall lifecycle, and the different habitat types interact in complex ways that are vital to their functionality and long-term existence. To preserve biodiversity in the Nashua River watershed, we need to work at the landscape level, protecting not just individual species, specialized and rare habitats, or isolated pieces of land, but an integrated matrix of natural areas of sufficient size, variety, and connectedness to maintain all our native species over the long term.

Genetic Diversity
Genetic diversity within local populations is another important factor to consider. Within a particular species or local population, individuals have genes that vary slightly from one another. Maintenance of some degree of genetic variability is necessary for the long-term continuance of the population or species, because different individuals will have different abilities to adapt to changing habitat or climatic conditions, disease, or other threats, and because of the detrimental effects of inbreeding.

Habitat Fragmentation
Maintaining a variety of habitat types, with adequate representation of each type and connectivity between habitat patches is also important for maintenance of biodiversity at broader landscape and ecosystem levels. As natural areas become fragmented and isolated from one another by roads, dams, and development, it is more difficult for individual plants or animals to move from one habitat patch to another. If a small population of a particular species is "stranded" on an island of habitat, it is vulnerable to the negative genetic effects of inbreeding, or to loss due to random events.

Recolonization by individuals traversing roads and development is particularly unlikely for small, slow moving creatures like reptiles or amphibians, or for certain woodland wildflowers whose seeds are dispersed only by ants and gravity. When one considers the risks presented to a frog, turtle, or snake attempting to cross a road, it is not surprising to learn that 53 percent of Massachusetts' native reptiles and 29 percent of our amphibians are listed under the Massachusetts Endangered Species Act as endangered, threatened, or of special concern. The Nashua River Valley is home to the state's largest and most viable population of the Blandings turtle (listed by the state as a threatened species). Keep an eye out in late May and early June for turtles, and help nesting females safely cross roads (BUT NEVER RELOCATE ANY WILD ANIMAL TO AN ENTIRELY DIFFERENT LOCATION). The Blandings turtle is distinctive and can be recognized as a medium to large black turtles with a high dome, dull yellowish radiating spots, and orange throat patch. Take photos anytime you think you've spotted a rare species, and submit the information to the Massachusetts Natural Heritage and Endangered Species Program in Westboro.

More mobile species can readily cross roads and development, and some are highly adaptable to the small patches of woods interspersed with lawns in residential areas. It is not surprising that highly mobile habitat generalists such as deer, skunks, and coyotes are thriving, and if anything are more common in suburban areas than in very rural locations.

Connecting Habitats for Viable Life Cycles
Many species rely on more than one habitat type during different parts of their lifecycle. Maintaining landscape connections between such habitats is crucial for protection of our local biodiversity. Amphibians are among the most obvious examples. Many species of amphibians such as wood frogs and spotted salamanders breed in vernal pools that typically contain water for only part of the year. This breeding habitat is essential because permanent bodies of water usually contain fish or other predators that would eat the amphibian eggs and larvae. However, vernal pool-breeding frogs and salamanders spend the majority of their life in adjacent, upland forests. They routinely range many hundreds or even thousands of feet from their breeding pools. If we protect a vernal pool but surround it with roads and development, the local amphibian populations are as likely to be doomed as if we had filled the pool with dirt and built a house on top of it. Amphibians are a major intermediate link in food chains in the forest ecosystem. Their loss degrades local environments in many more important and subtle ways than the simple loss of a few species.

Stopping Invasive Species
Protecting biodiversity is not just about maximizing the number of species that exist in one particular location. Many species present in our area, such as Autumn olive, purple loosestrife, and buckthorn, are invasive exotics that originated in other parts of the world. When initially introduced to a new location, their addition increases the total number of species located there. However, invasive exotic plants tend to take over and crowd out native species, thereby altering the habitat for native animals living in that location, and ultimately interfering with the functioning of the local ecosystem. Invasive exotics also include animals like the gypsy moth or hemlock wooly adelgid and diseases such as Dutch Elm disease or Chestnut blight. Thus, even tiny insects or microscopic organisms can have devasting effects on native biodiversity.

Biodiversity Protection Strategies
So, how can we protect biodiversity in the Nashua River watershed? One important way is by taking a broader, landscape level approach to land protection. Instead of protecting individual parcels of land, we should attempt to protect an interconnected network of viable natural habitats. Special habitats such as localized clusters of vernal pools and their surrounding forests should be targeted for acquisition in local Open Space Plans. Open space planning at the broader basinwide level should seek to set aside adequate, functional representatives of all naturally occuring habitat types. Large core areas of protected habitats should be connected through corridors, not only along rivers and streams but also in other natural wildlife corridors such as ridgetops. A basinwide land protection plan for the Nashua River watershed was developed by the Massachusetts Audubon Society. The Massachusetts Natural Heritage and Endangered Species Program has prepared a statewide Biomap that identifies the most important parts of the landscape to target for protection of both rare and common species and habitats.

Ecological Management
Finally, we should recognize that simply designating land as protected open space may not be sufficient to protect its functionality and biodiversity value. Active management measures may be needed. For example, grasslands must be mowed or burned to maintain habitat for wildlife dependent on early successional habitat. Invasive plant control activities should be increased along with landowner education aimed at minimizing additional introduction and spread of invasive species. As the science of "ecological restoration" evolves, we should consider doing more than passively letting our forests mature. For example, native wildflowers, trees, and shrubs that are uncommon due to past land use can be reintroduced in certain areas if appropriate local stock is used.


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