Human Health Risk
Invasive plants
Ecological Risk
Socioeconomic Risk
M
M
Plants termed “exotic” species were introduced in North America either accidentally or
intentionally from other parts of the world. Because these tend to have few if any natural
predators or parasites on this continent, they are aggressive competitors for space
and nutrients, and often form dense stands or thickets that crowd out native vegetation.
Other invasive plants, such as the common reed, are native species that have spread
out of control as a result of land disturbances that altered the original ecological balance.
What’s at risk?
STRESSOR SUMMARIES
In addition to the loss of plant biodiversity, wildlife
that depend on the displaced native species as a
food source are also affected. Most invasive species
flourish in disturbed habitats statewide, though they
tend to be somewhat less prevalent in the Pine
Barrens and coastal plains regions.
What are the ecological impacts in New
Jersey?
Common to all invasives is a tendency for prolific
seed dispersal and/or vigorous spread via root or
rhizome. They also share competitive advantages
such as the ability to germinate in shady, overly dry,
or overly moist conditions. The table below
summarizes the threats from common invasive
plants.
What are the socioeconomic impacts in
New Jersey?
Because of the many uncertainties associated
Scientific/ Common name
Type
with quantifying the extent of impacts, the estimated costs associated with the control of invasive
plant species range widely, from about $50 million
to $150 million. Many people find these plants
attractive, thus there are assumed to be no significant aesthetic or psychological costs incurred.
What’s being done?
There are no regulations for curbing the spread
of invasive plants. Moreover, many continue to
be sold and planted as ornamentals. Large-scale
control efforts are generally not feasible, and
would require years of vigilant eradication and
subsequent reseeding of native vegetation. New
Jersey DEP is collaborating with the New Jersey
Department of Agriculture on the development
of effective biological controls—the introduction of a leaf-eating species of beetle has had
promising results with reducing purple loosestrife.
Key Threats
Ailanthus altissima Tree-of-heaven
Tree
Affects abundance of important wildlife food
sources such as Black Cherry and Black Walnut.
Acer platanoides Norway maple
Tree
Still one of the most commonly planted street trees
in New Jersey. Unlike most invasives, also invades
undisturbed habitat. Outcompetes other species.
Rosa multiflora Multiflora rose
Shrub
Once championed for use as wildlife cover and
erosion control, forms impenetrable thickets and
outcompetes other species, reducing abundance of
native vegetation.
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Final Report of the New Jersey State Comparative Risk Project
Invasive plants (cont.)
Type
Key Threats
Berberis thunbergii Japanese barberry
Shrub
Still sold commercially as an ornamental shrub; can
tolerate low light, thus invading deep into forests
with closed canopies.
Celastrus orbiculatus Asiatic bittersweet
Woody
vine
Native populations of American bittersweet are
particularly at risk from competition and hybridization with Celastrus.
Lonicera japonica Japanese honeysuckle
Woody
vine
Tolerates low light and forms dense stands in forest
understory. Twining growth habit can damage/kill
other plants, including rare species.
Alliaria petiolata Garlic mustard
Biennial
Rapid spring growth may preclude emergence of
important food species. Primary spread is via human
transport (hiking, mowing).
Lythrum salicaria Purple loosestrife
Perennial
Invades wetlands. Direct threat to several state and
federally endangered species. All limestone fens in
northern New Jersey are seriously impacted.
Microstegium vimineum Japanese stilt grass
Annual
Forms dense “lawns” on disturbed sites. Particularly
invasive on fertile sites disturbed by flooding.
Increasing in New Jersey at exponential rates.
Phragmites australis Common reed
Perennial
Native species, the invasive spread of which appears
to be associated with land disturbing activity. Has
catastrophic effect on salt hay farming.
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Final Report of the New Jersey State Comparative Risk Project
STRESSOR SUMMARIES
Scientific/ Common name