Invading Exotics:
New Jersey Under Siege

Untutored in the biological sciences, the majority of the public will mistake the current landscape vegetation as being natural. For example, at an art and photography show some years ago, I was surprised and disappointed to see the invasive plant, purple loosestrife, depicted. In bloom the plant produces attractive lavender flowers and hence adds color to an otherwise monochromatic scene of early spring browns.

Invasive species threaten the diversity or abundance of native species, ecosystem stability, or commercial and recreational activities. Invasive species must be managed to prevent new and expanded infestations and to restore or improve natural communities while minimizing change to ecosystem structure and function.

Invasive species come from all over the world. They can be categorized according to their impact on native fish and wildlife populations. Although in almost all cases nonindigenous species have caused major problems, the most noxious of the list of invasive species include Old World rats (Rattus spp.), European starling (Sturnus vulgaris), house sparrow (Passer domesticus), rock dove or pigeon (Columba livia), common carp (Cyprinus carpio),
flathead catfish (Pylodictis olivaris), common reed (Haplotype M), purple loosestrife, Eurasian watermilfoil (Myriophyllum spicatum), Japanese knotweed (Polygonum cuspidatum), and a number of other plants native to Japan (Japan has a climate similar to New Jersey). On the next tier are native species that can become destructive due to an artificial environment that encourages overpopulation, such as resident Canada goose (Branta canadensis). Other invasives are less conspicuous. Consider the Asian tiger mosquito (Aedes albopictus) and Japanese rockpool mosquito (Ochlerotatus japonicus), both transmitters of the West Nile virus (Flavivirus).

Not every introduction of nonindigenous species has resulted in an ecological disaster. For example, the ring-necked pheasant (Phasianus colchicus), introduced from China in the mid 1800s, may have overlapped the niche of the extinct heath hen (Tympanuchus cupido cupido). Similarly, the brown trout (Salmo trutta), a species native to Europe, has become a popular game fish in the State.

Fortunately, New Jersey has been spared invasive species that require formidable control efforts once established, such as nutria (Myocastor coypus), although unconfirmed sightings have been reported in Salem County. Other invasives, such as zebra mussel (Dreissena polymorpha) and the Asian longhorned beetle (Anoplophora glabripennis), have only recently entered the State.

Leading culprits jeopardizing native plant communities especially in wetlands include: Phragmites Haplotype M forming wetland monocultures; purple loosestrife dominating freshwater wetlands; Eurasian watermilfoil choking many waterways; and multiflora rose (Rosa multiflora) overtaking abandoned fields. Apparently ignored by wildlife as a food source, Asian grasses have begun to appear in our forest understory, replacing indigenous plants. European starling and house sparrow are widespread bird pests that were introduced here in the last century and continue to disrupt our native bird populations, especially the nesting competition house sparrows give purple martin (Progne subis). Unfortunately, a major predator of native wild birds is another exotic species—the domestic cat (Felis silvestris). As many as 100 million feral and pet cats range freely across America and can cause hundreds of millions of songbird mortalities a year!

Unchecked, unwanted species wreak havoc on native populations and biodiversity. Plant species diversity is diminished, and a loss of vegetative community structure will result in a decrease in wildlife reproductive cover and food production. Some invasives, especially Phragmites, can develop dense stands of highly-combustible material during the dormant season, which can increase fire hazard, conceal vistas and natural landscapes, retain pools of water that become mosquito-breeding areas, and result in hydrologic disturbance such as tidal restriction. Other invasives, such as purple loosestrife, can rapidly alter the vegetational community structure of freshwater wetlands found throughout New Jersey, and reduce habitat suitability for threatened or endangered species such as the bog turtle (Clemmys muhlenbergii).

Public education, blocking pathways for future introductions, on-the-ground control (biological, mechanical or chemical methods), and habitat restoration are crucial to stemming this invasion of alien species. The Service has several programs that offer habitat restoration, including the Partners for Fish and Wildlife program, Bring Back the Natives, and the Coastal program. Without management and control of alien species, native fish and wildlife resources will continue to be impaired. The first line of defense needed in New Jersey is the development of an Invasive Species Management Plan. The New Jersey Invasive Species Council, recently established under Governor McGreevey’s Executive Order #97, has been directed to develop such a plan by June 2005. This plan will emphasize interagency collaboration and partnerships pursuant to federal Executive Order 13112, identify research needs, review and devise control methods, procure funding, implement two eradication/restoration projects by 2005, identify necessary legislative or regulatory actions, and educate the public.

Public concern drives public policy, and this issue of Field Notes will be effective if it inspires others to action to control and eradicate infestations, prevent future invasions, and reverse the deleterious effects that invasive species bring to our native wild populations. Remember, human activities are the primary cause of invasive species introductions; it is our responsibility to take appropriate actions to reverse these unwanted introductions.