CHAPTER
FOUR: BIOLOGICAL COMMUNITIES
PLANTS
Plant Communities:
The vegetation of Branford (Figure
7; Vegetation) cannot be considered "virgin" to
the landscape. Clear-cutting for agriculture earlier
in its Colonial history and more recently the landscaping
of lawns and parks, the introduction of escaped ornamentals
and other introduced species, and the expansion of invasive
plants have significantly changed the nature of the
vegetation within the entire region. Therefore it is
not necessary to discuss natural plant communities.
Instead the following discussion will concentrate on
existing plant community structure and will not include
managed areas within residential or commercial developments.
The plant communities of Branford can be divided into
many different habitats based on the presence of dominant
plant species. For purpose of discussion the vegetation
of the watershed will be divided into three major categories:
upland, wetland, and agriculture. The plant lists are
not meant to be exhaustive, but, rather, to provide
an overview of the more dominant associations. Plant
taxonomy is after Gleason (1952), Fernald (1970), Sutton
and Sutton (1986) and Niering (1986).
The upland plant communities are divided
into the following cover types:
• early-successional field
• late-successional field
• deciduous forest/riparian
• coniferous forest/riparian
• introduced species
Agriculture is separated based on dominant
crop and includes:
• herbaceous farm
• tree farm
• grazing pasture
Wetland communities are separated into:
• freshwater non-tidal swamp (with trees)
• freshwater non-tidal marsh (without trees)
• freshwater non-tidal bog (heath shrubs and moss)
• vernal pools and intermittent watercourses
• freshwater tidal marsh
• brackish tidal marsh
• tidal salt marsh
• aquatic and subtidal
Upland Plant Communities
Early-Successional Field
- are fields that have recently been abandoned and are
dominated by herbaceous plants and low vines (you can
generally see over the tops of the plants). Species
diversity in these fields is very high and a lot of
pioneering species can be found persisting in the community.
Grasses tend to dominate these areas and include foxtail
(Setaria, spp.), redtop (Agrostis sp.), fescue (Festuca
spp.), and a variety of species belonging to the genera
Panicum, Poa, Eragrostis and Aristida among others.
Non-grass plants commonly found here include dandelions
(Taraxacum spp.), clover (Trifolium and Lespedeza),
plantains (Plantago spp.), asters, cinquefoil (Potentilla
spp.), buttercups (Ranunculus spp.), St. Johnswort (Hypericum
spp.), goldenrods, yarrow (Achillea spp.) and smartweeds
(Polygonum spp.) among others.
Late-Successional Field
- refers to old fields that have been allowed to revert
back towards a forested condition. The late-successional
field is composed of shrubs, small trees, and herbaceous
plants. Trees common to these areas include white and
gray birch (Betula papyrifera and populifolia), red
cedar (Juniperus virginiana), black cherry (Prunus serotina),
choke cherry (Prunus virginiana), and young oaks. Shrubs
common to these areas include red stemmed (Cornus stolonifera)
and gray (C. racemosa) dogwoods, sumac (Rhus spp.),
pussy willow (Salix discolor), alder buckthorn (Rhamnus
frangula), and maple leaf viburnum (Viburnum acerifolium).
These fields often support large amounts of vines and
vine-like plants including poison ivy (Toxicodendron
radicans), virginia creeper (Parthenocissus quinquefolia),
grape (Vitis spp.), raspberries (Rubus spp.), currant
(Ribes spp.), greenbrier (Smilax spp.), morning glories
(Ipomoea spp.), and honeysuckle (Lonicera spp.), and
a large population of introduced species such as multiflora
rose (Rosa multiflora), Chinese wisteria (Wisteria sinensis),
oriental bittersweet (Celastrus orbiculata), garlic
mustard (Alliaria officinalis) Japanese knotweed (Polygonum
cuspatatum) and Japanese honeysuckle (Lonicera japonica).
Herbaceous plants are also common in these late successional
fields and include ragweed (Ambrosia sp.), goldenrods
(Solidago spp.), Queen Anne's Lace (Daucus carota),
beggar's ticks (Bidens spp.), asters (Aster spp.), sunflower
(Helianthus spp.), thoroughworts (Eupatorium spp.),
thistle (Cirsium spp.), loosestrife (Lythrum spp.) and
a variety of grasses.
Deciduous forest - can also
be further divided into upland and riparian/floodplain
forests and is the most dominant upland plant community
within the Town. Deciduous forest is generally dominated
by combinations of oak (Quercus spp.), maple (Acer spp.),
and hickory (Carya spp.) and a variety of co-dominants
such as ash (Fraxinus spp.), cherries (Prunus spp.),
poplar (Populus spp.), tulip tree (Liriodendron tuliperfera),
walnuts (Juglans spp.), sassafras (Sassafras albidum)
and birch (Betula spp.). A host of understory plants
share the forest floor and include dogwood (Cornus spp.),
arrow-wood (Viburnum dentatum), winterberries (Ilex
spp.), shadbush (Amelanchia spp.), cherries (Prunus
spp.) and laurels (Kalmia spp.).
The upland deciduous forest is dominated by oaks (Quercus
spp.) with red oak (Q. rubra) and white oak (Q. alba)
accounting for a majority of the oak trees. The next
most abundant trees are the hickories and include the
shag-bark hickory (Carya ovata), bitternut hickory (C.
cordiformis), pignut hickory (C. glabra) and mockernut
hickory (C. tomentosa). In many of the younger forested
areas, oaks are mixed with birch, red cedar and black
cherry. In disturbed habitats, oaks can be found in
association with trembling aspen (Populus tremuloides).
In the forested areas within the more urbanized zones,
oaks can be found mixed with a number of introduced
species such as tree of heaven (Ailanthus altissima),
European (horse) chestnut (Aesculus hippocastanum) and
Norway maple (Acer platanoides). The maples (Acer spp.)
are also important trees in the upland forest and include
sugar maple (A. saccharum), silver maple (A. saccharinum),
and to a lesser extent red maple (A. rubrum).
Throughout the Town, the oaks are found in different
associations. The most common association is oak/hickory
with red oak being the dominant oak species. Oak and
maple are often associates, as are oak/maple/hickory
associations. On some ridgetops along the Jurassic fault
line, white oak forms associations with hickory and
sassafras. At the Supply Ponds, oak/maple associations
are common and swamp white oak may be found along the
wetter areas.
The riparian/floodplain deciduous forest is dominated
by pin oak (Q. palustris) and red maple (A. rubrum).
Within this zone, other tree species may include sycamore
(Platanus occidentalis), eastern cottonwood (Populus
deltoides), willows (Salix spp. including the introduced
weeping willow - S. babylonica), black locust (Robinia
pseudoacacia), sweetgum (Liquidambar styraciflua), elm
(Ulmus americana), swamp white oak (Q. bicolor), and
black ash (F. nigra), the latter two also commonly found
in swamps.
In a number of locations, power line right-of-ways bisect
forested areas. In order to keep the area free of large
trees these right-of-ways are cut and planted with various
shrub species. Plants common to the right-of-ways include
alder, sumac, Russian olive (Elaeagnus angustifolia),
poison ivy, pussy willow, morning glory, Japanese honeysuckle,
wisteria, goldenrod, deer-tongue panicum (Panicum clandestinum),
asters, switchgrass (Panicum virgatum), Queen Anne's
Lace, ragweed, raspberries, loosestrife, and reedgrass,
among others.
Coniferous forest - are
forested areas dominated by Gymnosperms (Coniferophyta)
including pines, hemlock, spruce, and fir. Coniferous
forest accounts for about 5% of the total forested area
and most are the result of plantations. Coniferous forests
can be further divided into upland and riparian forests,
the latter most important for protecting streams and
rivers.
Within the Town, the coniferous upland forest community
type can be further subdivided into mixed hardwood (deciduous)-coniferous
and coniferous forests. The mixed hardwood/coniferous
forest includes two major associations: the hemlock/beech
mixed association and the white pine/hickory association.
The coniferous forest type is typically the result of
plantings on abandoned fields. These forests are comprised
of stands of white pine (Pinus strobus), and/or Norway
spruce (Picea abies), although hemlock may be locally
important. Other plantations include European larch
(Larix decidua), white spruce (Picea alba), and northern
white cedar (Thuja occidentalis). These stands are typically
maintained by the selective cutting of hardwoods.
One of the best examples of existing hemlock/beech mixed
forest type can be found along the slopes and streams
running through North Farms Park located just over the
border in North Branford. Judging by the size of some
of these hemlocks, portions of this stand are between
75 and 100 years in age. Along with the hemlock and
beeches, the canopy also includes black birch (Betula
nigra), red oak, tulip tree, red maple, shagbark hickory,
mockernut hickory, bitternut hickory, pignut hickory,
and some white oak. The understory in this area is a
mix of shrubs including sassafras (Sassafras albidum),
mountain laurel (Kalmia latifolia), witchhazel (Hamamelis
virginiana), dogwood, American hornbeam (Carpinus caroliniana),
arrowwood, and saplings such as red maple and black
birch. Herbs in the understory include raspberries (Rubus
spp.), false Solomon's seal (Smilacina racemosa), Canada
mayflower (Maianthemum canadense), wood aster (A. divaricatus),
path rush (Juncus tenuis), goldenrod and a variety of
ferns including Christmas fern (Polystichum acrostichoides),
hayscented fern (Dennstaedtia punctilobula), and lady
fern (Athyrium Filix-femina).
The riparian/floodplain mixed coniferous forest is similar
in structure to the upland coniferous mixed forest type
except for the understory that is dominated by more
moisture tolerant species. Along stream banks and wetter
areas, other woody species such as sweet pepperbush
(Clethra alnifolia), alder (Alnus spp.) and red maple
become important and a variety of herbaceous plants
such as jewelweed (Impatiens capensis), smartweed (Polygonum
spp.), duck potato (Sagittaria latifolia), and skullcap
(Scutellaria spp.) can be found growing in slow moving
reaches of the stream. The riparian coniferous forest
is typically dominated by hemlock, although stands of
white pine may also be found along floodplains.
In many areas, hemlock has been dying due to infestation
by the wooly adelgid. This pest is severely limiting
hemlock and may one day eliminate this plant from the
Town except where it is maintained through spraying.
Another mixed coniferous forest type is the white pine/hickory
association. The most common hickory is the mockernut
hickory, although, bitternut and shagbark hickories
can also become important. At the Supply Ponds, red
maple also becomes a co-dominant in this association
in many areas. The understory also varies between sites
and includes American hornbeam, witchhazel, arrow-wood,
dogwood, winterberry (Ilex verticillata), and the introduced
winged Euonymus (Euonymus alatus).
The coniferous forest community is dominated by white
pine associations. Although many of these areas have
been maintained (selectively cut, planted), they have
become an important upland forest community. The best
example of this forest type can be found in pockets
surrounding Regional Water Authority land along Lake
Saltonstall. In many of these areas the white pine may
be mixed with Norway spruce and/or red spruce. Red pine
is present in the forest but most of the specimens are
relatively young suggesting recent cutting of this species.
Frazier fir is also found in the area but these are
almost exclusively found planted in Christmas tree plantations
(neat rows with regular spacing). In some places the
white pine also includes associations with hemlock,
although the hemlock tends to favor ravines and lowland
areas. The understory in this forest type contains a
variety of species including blueberry (Vaccinium spp.),
poison ivy, raspberries, asters, Virginia creeper, and
Japanese honeysuckle.
Agriculture
Agriculture accounts for approximately 10% of the land-use
within the Town. Most of the agricultural fields are
devoted to corn and pasture land with orchards locally
important. Tree farms are present in the Town and many
are used to grow Christmas trees, although red pine
and white pine plantations are also evident. Agricultural
fields may be further subdivided into tilled (vegetation
is periodically removed) and untilled fields (periodically
maintained by mowing, when not mowed will form the early
successional field). Small farms are spread throughout
the Town with a majority of them located north of I-95
and to a lesser extent, along the Guilford line.
Agriculture has had a major impact on the entire region.
During the last three hundred years, all habitats have
at one time or another been clear-cut and most have
been plowed. Farming activities since European settlement
have eliminated all virgin forests and have had a major
impact on plant community structure in these areas.
For instance, American chestnut (Castanea dentata) and
hickory were not forest dominants prior to European
settlement. Chestnut dominated the regrowth of cut forests
between the 1600's and the twentieth century before
succumbing to an Asiatic blight during the early 1900's.
Once chestnut died off, hickory and oak were able to
replace it in the forest canopy. Thus, the oak/hickory
association is a relatively new plant grouping in these
forests. There is also some evidence that coniferous
forests were more prevalent in the Town and have since
been replaced by the deciduous forest type. Since these
forests are relatively young, trees such as birch and
red cedar (left-overs from late succession) are more
prevalent then we would expect to see in mature forests.
Similarly, the proliferation of vines and vine-like
plants is a direct result of repeated forest cuts during
the last few centuries that have resulted in opening
up the canopy to sufficient light to allow for extensive
understory growth. The vast majority of early and late
successional fields are also abandoned farm fields.
The forests and many of the wetland habitats that we
see today are secondary growth habitats with the oldest
continuous areas typically being less than 150 years
in age.
Wetland
Since wetland areas were hardest to farm without extensive
draining and tilling many survived human activities
during the last few centuries. This does not suggest
that they survived untouched, it just supposes that
the area had a better chance of remaining wetland for
longer periods of time. Although any one type of wetland
may have a long history within the watershed, many of
these wetland areas are relatively new to the sites
in which they are presently found because the landscape
has been altered and the hydrology has been extensively
manipulated. Even wetlands that have maintained their
place on the landscape for many centuries have also
changed significantly through the years (i.e., hydrology,
vegetation). The only class of wetlands that have escaped
relatively untouched are the tidal salt marshes, although
here too, the marshes have been hayed, ditched for mosquito
control and diked off to reclaim the land for development
or to allow for a road or railroad crossing. Today wetlands
are protected by law; however, with continued development
and the need to control hydrology (i.e., storm water
discharge, increased impervious cover) these habitats
are still stressed and are experiencing shifts in plant
community structure. Like the upland habitats, wetlands
can be separated into divisions based on the dominant
vegetation and hydrology. [NOTE: freshwater refers only
to the absence of salts, it does not denote water quality]
Non-Tidal
Freshwater swamps - are
wetlands that are dominated by trees. Within the Town,
the most common swamps are dominated by red maple. Pin
oak, swamp white oak, and black ash are also important
species and may locally become co-dominants. Shrubs
such as sweet pepperbush, alder, American hornbeam,
and buttonbush (Cephalanthus occidentalis) are common
in the understory. Other species of note include black
willow (Salix nigra), highbush blueberry (Vaccinium
corymbosum), spicebush (Lindera benzoin), and black
birch (B. lenta)). The swamp habitat is wet for most
of the year and is characterized by limited herbaceous
ground cover.
Freshwater marshes - are
wetlands dominated by herbaceous plants. Dominant species
include tussock sedge (Carex stricta), jewelweed, cattail
(Typha spp.), skunk cabbage (Symplocarpus foetidus),
smartweed (Polygonum spp.), canary grass (Phalaris arundinacea),
arrow arum (Peltandra virginica), duck potato (Sagittaria
latifolia), and a variety of sedges and rushes including
those of the genus Scirpus (i.e., S. cyperinus, S. fluviatilis),
Cyperus (i.e., C. strigosus), Carex (i.e., C. crinata,
C. lurida), Eleocharis (i.e., E. obtusa) and Juncus
(i.e., J. effusus). Reedgrass (Phragmites australis)
has been spreading recently and now dominates a number
of sites. Although this plant is native to Connecticut,
it has become an invasive species (a non-native genotype
has now been confirmed growing in the area) and now
grows in areas historically not typical of the plant.
Introduced species such as multiflora rose and Japanese
knotweed have acclimated to many of these habitats as
well, particularly along the upper borders. Freshwater
marshes are characterized by hummocky topography, peaty
substrates, and saturated ground water conditions. Although
natural to the landscape, many marshes are the result
of damming and diversions of river, stream flow, and
storm water drainage during the last few hundred years.
Freshwater Shrub/Scrub Wetlands/Bog
- are wetlands dominated by woody shrubs. Although these
wetlands are less common in the watershed, a few examples
do exist within Town, most notably along Quarry Road.
In these habitats, swamp azalea (Rhododendron viscosum),
alder, buttonbush, dogwood, spicebush, steeplebush (Spirea
tomentosa), and sweet pepper bush can be found. Bogs
in Town are few and far between. They differ from the
shrub/scrub wetland by having shrubs interspersed with
sphagnum moss, and various associations with tussock
sedge, sensitive fern (Onoclea sensibilis), and jewelweed.
Some examples can still be found in the Pisgah/Queach
Brook subwatershed along the utility right-of-way around
the Supply Ponds.
Vernal Pools/Intermittent Watercourses
- are wetland areas that dry out for a portion of the
year. Although not dominated by any one vegetation type,
they are important breeding habitats for amphibians.
Vernal pools are wet in the spring and are common in
red maple forests (not necessarily swamps). These may
vary in size, although most are typically a few square
yards in area. Typically, these pools are limited in
vegetation and are small depressions where leaves may
accumulate. During much of the year, they are drained
and not very obvious. A recent inventory of vernal pools
for the Town's Conservation and Environment Commission
found 55 pools scattered on public and quasi-public
property (private land was not surveyed) throughout
the town (Dr. N. Proctor, Survey of Branford Vernal
Pools, Report to the Conservation and Environment Commission,
May 31, 2002). Information on each pool is on file with
the commission.
Intermittent watercourses are those that have a defined
channel and exhibit some form of surface flow such as
alluvial sediments (sands and muds carried by water)
or wrack (plant debris or floatables that come to rest
in tree branches or rocks). Water flows occur during
storm events and support a variety of plants including
sedges, jewelweed, and cattail. Although many of these
watercourses are located in wooded areas, there are
many that are grass-covered and incorporated into lawns
and fields.
Aquatic - refer to areas
that are under water for most of the time. In freshwater
aquatic habitats, vegetation may include waterweed (Potamogetan
spp.), water marigold (Megalodonta beckii), duckweed
(Lemna minor), arrow arum, duck potato, and water lily,
among others.
Tidal Wetlands
Freshwater tidal marshes
- are tidally influenced wetlands that are inundated
in freshwater and dominated by herbaceous plants. Because
dams and road culverts block the path of water, most
of this type wetland is limited to small bands along
the upper-most reaches of the Branford River (near I-95)
and some of the smaller tributaries such as Queach Brook.
The vegetation here is dominated by jewelweed, cattail,
arrow-arum, a variety of sedges and reedgrass. Water
lily (Nymphaea odorata), and duck potato can also be
found in the wetter areas.
Brackish marshes - are tidal
marshes that are inundated with tidal waters with a
salinity of less than 18 ppt. The dominant plants in
these marshes include reedgrass, saltwater cord grass,
salt hay, blackgrass and a variety of sedges (Scirpus
robustus, Scirpus maritimus and Scirpus olneyi). Aster
and goldenrod may also be important locally. These marshes
are prevalent between the freshwater and salt marshes
in the lower river/harbor and small tributaries. The
best example of this type marsh can be found between
the Branford High School and Route 1 and along the lower
reaches of Queach Brook.
Today brackish marshes are also prevalent where roads
have bisected a coastal marsh and have restricted tidal
flows. This restriction in flow reduces saltwater inputs
and eventually, with enough rain, the soils in these
systems become diluted. The change from salt water to
brackish conditions leads to a change in the plant community
as well. Many of these areas are now supporting monocultures
of reedgrass (e.g., upper Mill Creek). Attesting to
the changes in tidal hydrology, many of the marshes
still contain pockets of salt marsh plants such as salt
hay and spikegrass (Sybil Creek above Route 146) and
a variety of transition zone species such as salt marsh
bulrush (Scirpus robustus), goosefoot (Atriplex patula),
dock (Rumex spp.), and saltmarsh fleabane (Pluchea purpureascens).
Salt marshes - are marsh
systems dominated by tidal hydrology and regularly inundated
with full strength seawater (Long Island Sound is typically
about 25 ppt). These marshes are dominated by grass
including saltwater cordgrass (Spartina alterniflora),
salt hay (Spartina patens), spikegrass (Distichlis spicata),
blackgrass (Juncus gerardii), and a variety of non-grass
plants such as seaside goldenrod (Solidago sempervirens),
salt marsh aster (Aster tenuifolius), sea lavender (Limonium
nashii), and glassworts (Salicornia spp.).
The transition zone between freshwater and saltwater
is very diverse and includes the natural habitat for
reedgrass. In this upper border transition zone, it
is also common to find rose (Rosa rugosa and Rosa multifora),
poison ivy, marsh elder (Iva frutescens), marsh mallow
(Hibsicus palustris), waterhemp (Achnida cannabina),
goosefoot, bulrush and fleabane.
Subtidal - refer to areas
that are under water for most of the time. The subtidal
zones are located in the lower reaches of the harbor
and historically included widgeon grass (Ruppia sp.)
and possibly eelgrass (Zostera sp.), although the latter
is subject to debate (a disease has killed much of this
species within this century and records are not clear
as to the distribution of this species prior to this
century). The subtidal zone also includes green algae
(Enteromorpha intestinalis), knotted wrack (Ascoplyllum
nodosum), rockweed (Fucus vesiculosus) and sea lettuce
(Ulva lactuca).
ANIMALS
Animal Communities:
Animal communities are more difficult to define than
plant communities because the animals are able to move
around. Instead, it is often easier to divide the animals
based on the phylum (major subdivision) to which they
belong (insect, arthropods, amphibians, reptiles, birds,
mammals).
During the last few centuries, animal populations have
changed dramatically in the Town in response to changes
in land-use. Clearcutting during the 1700's changed
the nature of the animal community from woodland species
to open field species. Additionally, many animals have
been introduced to the habitat either intentionally
(i.e., pigeons) or by accident (i.e., Norway rats).
In other cases, competition for food and protection
of livestock led to the elimination of certain species.
For example, bears and coyotes were pushed out of the
area by the 1800's. Although both species are making
a comeback in Connecticut, coyotes have come back to
the Town while bears are still north of Town. Other
animals that were probably more prevalent in the past
include beavers, otters, and muskrats.
Urbanization has also had an impact on animal communities
throughout the watershed. European starlings, house
sparrows, rats, mice, skunks, squirrels and raccoons
have all adapted well to the urban environment and,
at present, dominate many habitats within Town. Urbanization
has also led to an increase in feral cat populations.
Although data are limited, there are some inferences
that can be made about the impacts of recent residential
development within the Branford River watershed. A survey
of reptiles in Branford during the late 1940's found
10 of the 15 species of snake and 8 of the 10 species
of turtles known to exist in Connecticut were found
at both Ward's Millpond and the Supply Ponds (Finneran
1948). This included the northern ring-neck snake (Diadophis
punctatus), eastern hog-nose snake (Heterodon platyrhinos),
northern black racer (Coluber constrictor), eastern
garter snake (Thamnophis sirtalis), black rat snake
(Elaphe obsoleta), eastern milk snake (Lampropeltis
triangulum), northern water snake (Nerodia sipedon),
northern brown snake (Storeria dekayi), eastern ribbon
snake (Thamnophis sauritis) and northern copperhead
snake (Agkistrodon contortrix mokeson), and stinkpot
turtle (Sternotherus odoratus), common snapping turtle
(Chelydra serpentina), spotted turtle (Clemmys guttata),
wood turtle (Clemmys insculpta), northern diamondback
terrapin (Malaclemys terrapin), painted turtle (Chrysemys
picta), eastern box turtle (Terrapene carolina) and
Emys blandingii. A survey conducted at these sites during
the 1990's found that only the northern ring-neck snake,
northern black racer, eastern garter snake, eastern
milk snake, and northern water snake and common snapping
turtle, spotted turtle, wood turtle, and eastern painted
turtle could be confirmed living in the area. That means
that snake diversity (number of species within the watershed)
has declined 50% and turtles over 35% in the last fifty
years. More telling signs include changes in population
of each species. For example, the northern brown snake,
copperhead snake, the stinkpot turtle and the eastern
box turtle were common during the 1940 survey and are
now listed as species of special concern. A more complete
list of animal species found in Branford is found in
Appendix I.
RARE AND ENDANGERED SPECIES
Due to the importance of rare and endangered species,
the State maintains a list of species and their habitats.
Species are listed according to county (Appendix
II: Rare and Endangered Species) and areas of special
concern are mapped and noted by Town (Figure
8: Areas of Special Concern). To prevent collection
of these species, site-specific information is not made
public. If you are located in one of the areas of special
concern and interested in obtaining potential rare or
endangered species lists for your parcel of land, you
must contact the CTDEP directly for the information.
INTRODUCED/INVASIVE SPECIES
Introduced and invasive species have become important
in the plant and animal communities in Town. Their distribution
varies throughout Town and they are typically found
both in managed environments (i.e., road sides) and
in many natural areas. Although most of these species
were brought here to either help contain erosion or
used for ornamental purposes (e.g., weeping willow,
Russian olive (Elaeagnus angustifolia), Mute Swans),
some were introduced by accident (e.g., garlic mustard,
Japanese knotweed). Of the plants that were brought
here for erosion control, the most dominant ones include
olive (Elaeagnus umbellata), and multiflora rose. One
of the best examples of olive/rose communities can be
seen at the old Cosgrove gravel pit off Tabor Drive.
Landscape plants that have escaped and became common
on the landscape include winged Euonymus, Japanese honeysuckle,
and purple loosestrife (you can still find many of these
species being sold in nurseries around Town).
Invasive species are those that have a native form that
have recently experienced a significant change in their
distribution patterns. The best example of an invasive
is reedgrass (Phragmites australis). A native form of
the plant has been here for thousands of years, but
an introduced variant from Europe has recently displaced
much of the native form and is now dominating many habitats.
Although many of the introduced and invasive plants
are mixed in other communities, they can become dominants
on the landscape and may pose additional threats to
native plant species in the future. A more complete
list of introduced and invasive species is found in
Appendix III.
The most prominent introduced animals species are the
European starling, Norway rat and Mute Swans. Starling
populations have grown considerably over the last decade
and Mute Swans have become pest species in many of our
ponds and watercourses (their territorial behavior is
quite often a problem to smaller native waterfowl in
the area). A recent introduction of the Monk Parrot
(escaped pet species) has added color and noise to the
environment. There are a number of imported insect populations
that have become important through the years. The wooly
adelgid and the Asian long-horned beetle are two examples.
The adelgid is currently decimating hemlock trees in
the region and the introduction of the long-horned beetle,
which attacks a number of coniferous species, is of
great concern. Other introduced species that pose a
risk to the environment include Pfisteria, a water-born
parasite that is killing coastal fish populations and
zebra mussels, a freshwater mollusk that is capable
of causing extensive fouling in engines and power plants.
Recent introductions of viruses (West Nile virus) have
also been of great concern. Some introductions are more
difficult to assess. For example, the Asian Lady Beetle
is an introduced insect that may have some positive
impact on the plant communities by eating aphids. Assessing
any introduced or invasive species is problematic because
of our prejudices of what may be beneficial or cute
to look at.
Some of the introduced species have become so common
that we consider them as naturalized species. Species
such as multiflora rose, weeping willows and pigeons
are considered by many to be very natural to the environment.
However, even though they have become part of the landscape,
it is still important that we realize that they still
have an impact on the native species that have evolved
here. Other organisms such as dogs, cats and cattle
are so domesticated that we no longer consider them
introductions to the landscape; however, when you consider
the time and energy put into these species (i.e., aisles
of food in the supermarket, pasture land), they have
impacts on the landscape that generally out-weigh the
impacts of many other introduced organisms.
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