Invasive Species

By Karen Dougherty

Imagine it is a warm, summer day and you decide to go out for a stroll. You pass a flock of starlings daintily stepping along the grass on their graceful, yellow legs. You pass some rose bushes and see the iridescent gleam of a Japanese beetle picking its way along the bush. As you pass by a small pond, beautiful purple loosestrife waves its purple flowers in the breeze. This seems to be an idyllic paradise, but actually it is a disturbing ecological scene that is being played out with alarming frequency all over the country, if not the world.

What do European starlings, Japanese beetles and purple loosestrife all have in common? They are highly invasive species that are wreaking havoc on delicate ecosystems and native species.

According to the Union of Concerned Scientists (USC), invasive species are those that “are a harmful subset of non-native, introduced species that adversely affect native plants and animals, change how ecosystems work, carry diseases to wildlife, plants, or people, or cause other damage. It is estimated that in this country alone, over 7,000 species of non-native plants, mammals, birds, amphibians, reptiles, fish, arthropods, and mollusks are established.” The US spends approximately 100 billion dollars per year trying to control damaging invasive species.

Some of these species, such as the European starling, were deliberately introduced. According to Cornell University, around 1890, 100 starlings were released in Central Park as part of a plan to bring to the US all the birds mentioned in Shakespeare’s works. Cornell reports that “today there are more than 200 million starlings across most of the continent."

Starlings are very aggressive and crowd out native bird species, even driving them from their nests. According to the UCS, “declining numbers of woodpeckers, Eastern Bluebirds, Purple Martins and Tree Swallows are thought to be a result of the starling population boom."

Purple loosestrife is a wetlands plant native to Eurasia. According to the New Jersey Department of Agriculture, purple loosestrife was accidentally introduced to North America in the 1800s. It can now be found in nearly every state and in Canada. In 1999, The US Fish and Wildlife Service (USFWS) estimated that control of purple loosestrife costs $45 million per year. So pervasive and devastating to fragile wetland ecosystems is purple loosestrife that the USFWS called it “Public Enemy #1 on Federal Lands.” New Jersey wetlands have been hit particularly hard by purple loosestrife. This is not so surprising, as a single plant can produce 2.5 million seeds per year.

Many other species have been accidentally introduced through importation of goods or in the ballast water of ships. The Zebra mussel is a prime example of this. The United States Geological Society (USGS) believes that the mussels arrived via transatlantic ships sometime around 1988, “a cargo ship takes on ballast water in one port and dumps it in another, along with any number of aquatic species.

The Zebra mussel has devastated aquatic ecosystems throughout the Great Lakes and the rivers and lakes of the US east coast. Southern California and Virginia have reported sightings. The Zebra mussel population has exploded, consuming vast amounts of phytoplankton. Native freshwater bivalves make their homes in the mud but because Zebra mussels attach themselves to any available hard surface, they clog pipes and damage boat hulls. Large numbers of their shells wash up on beaches.

It is believed that eradication attempts of the Zebra mussels have cost over one billion dollars. The Zebra mussel invasion has been so detrimental to our freshwater ecosystems that in 1990 the Non-indigenous Aquatic Nuisance Prevention and Control Act was passed, this later became known as the National Invasive Species Act (NISA) of 1996.

Invasive species are can also occur in the form of pathogens. The American chestnut tree once grew prolifically in the eastern United States. This tree was an extremely valuable wood resource. Unfortunately, when a few Japanese chestnut trees were planted in New York around 1904, they carried a fungus called chestnut blight. According to the UCS, the blight killed 180 million acres of American chestnut trees. Ten moth species that depended on the chestnut trees for survival also perished.

There are things we can do to minimize the threat of invasive species. The federal government, through the National Invasive Species Act, continues to monitor the threat of invasive species. In order to minimize invasive threats to our waterways, ships entering the US are required to release their ballast water in mid-ocean, and the Coast Guard is proposing that even tighter restrictions be put into place.

Many states have banned the sale of invasive plants. When buying plants choose species that are indigenous to your part of the country; this also provides food, shelter and protection for indigenous animals and insects that rely on these plants. Never release exotic pets into the environment. If you enjoy water activities such as fishing and boating, be sure that all items are carefully washed so as not to transfer aquatic organisms from one location to another.

It is only through responsible and diligent behavior that we can hope to repair our native ecosystems and encourage the survival of indigenous species. Already we have lost far too many plants and animals to careless and irresponsible behavior.


Karen Dougherty teaches preschool at Barnert Temple in Franklin Lakes, New Jersey. She holds a Bachelor of Fine Arts degree from the University of Miami and is currently pursuing a Bachelor of Arts degree in Environmental Studies from Ramapo College. Karen lives with her husband and two daughters in northern New Jersey.