Protecting Biodiversity in the Nashua
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 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.
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
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
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.
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.
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.