Invasive Species

Categories:  Features    Environment
Wednesday, May 14th, 2014 at 3:26 AM
Invasive Species by Mary Birdsong

Invasive Species

Sneaking in by foot, fin, or feather is one way they get here. They also hide in foreign conveyances like great lake cargo vessels, or are innocently invited in by us when greenhouses sell imported plants and we take them home. Most of the time we don’t see them, or understand their danger.

Until it is too late.

These interlopers are non-native animals, plants, and microorganisms that have been finding their way into places they are not welcome for as long as humans have traveled. This is nothing new. The black rat is believed to be the first animal to have been inadvertently distributed by humans, having reached Europe in the first century A.D. from tropical Asia via trading vessels.

The land and waters of Erie County are just as vulnerable as anywhere, perhaps even more so with a port that is open to world trade.

These interlopers don’t come with the intention to harm, just to live their lives. Some find — with no natural predators in this new territory — the ideal conditions to flourish. When that happens, they become what we call invasive species, a plant or animal that inhabits to the point of domination or detriment to the local ecology.

Zebra mussels may be the most well-known invasive species in our area. Believed to be stowaways in ballast water of cargo ships from Eurasia, the mussels were first discovered in Lake St. Clair in 1988. Their close cousins, quagga mussels, arrived a year later. Both quickly made themselves right at home in Lake Erie.

At first, their filtering capacity seemed like a good thing, as water clarity increased from about six inches to sometimes more than three feet. Not bad for a lake that had seen its share of nasty pollution. It was soon realized, however, that with ideal growing conditions and no natural predators, the mussels were swiftly clogging water intake pipes, damaging water equipment, altering water quality and decreasing food sources for native species.

The clarity has been found to be problematic, too. More sunlight reaching below the surface has encouraged harmful algae growth leading to large toxic blooms in Lake Erie over the past few years. The economic impact of these two small mussel species in Pennsylvania is in the billons of dollars in damage and repairs.

Mussels are just the tip of the non-native iceberg, however.

Also in Lake Erie are round goby, a small, robust fish that thrives in degraded water conditions. Also from Eurasia, the goby’s presence in the Great Lakes is both boon and burden. The gobies compete with native fish for food and habitat but they also feast on the invasive mussels, keeping the mollusks in check but not eradicating them. On the upside as well, the once-threatened Lake Erie watersnake is now making a comeback, as it finds gobies a tasty addition to its diet, and native fish, such as smallmouth and largemouth bass and walleye, are starting to prey on it. In fact, bait manufacturers are adding  “Great Lakes Goby” lures to their lines.

Some species, like the sea lamprey, may be native to part of a region but are naturally contained within certain watersheds. That is, until we open the floodgates.

Sea lampreys – jawless parasitic fish that attach to a host for hematophagous feeding – found their way into Lake Erie in 1921 through the Welland Canal that connects to Lake Ontario. Now the non-native species is playing a role in the diminishing steelhead trout, lake whitefish, burbot, and lake trout populations since the snake-like-looking fish often latches onto such native species, puncturing their skin with its suction-cup-like mouth filled with sharp teeth to feed off their bodily fluids.

And sometimes with invasive species, it’s like a domino effect. With no natural apex predator – lake trout in this case – other species go unchecked. Facing less threat from lake trout, alewife – a herring and another invasive species – rose sharply, altering the pre-lamprey ecosystem. And the sea lamprey – with no natural predator in the Great Lakes – can freely and aggressively roam, preying on hosts that lack a natural defense against it and continuing to throw the natural order of the ecosystem out of balance.

Land animals, such as the Norway rat and house mouse, traveled to the New World from the Old World along with immigrants. Both can be found in Erie and Crawford counties. Red-eared sliders, a type of turtle found in the pet trade, are released, illegally, across the country by pet owners no longer willing to care for the rapidly growing reptiles. The slider is an aggressive competitor for food, basking sites where turtles sit in the sun, and breeding habitat, posing a significant threat to many native turtle species, including the red-bellied turtle that is listed as threatened in Pennsylvania. Mark Lethaby, a herpetologist with the Natural History Museum at the Tom Ridge Environmental Center says that there is a resident population of red-eared sliders at Presque Isle State Park. “We don't know if they are reproducing there, though,” he says.

Humans also aided the passage of European starlings, English house sparrows, and mute swans into the country. The sparrows and starlings were introduced, in part, by the American Acclimatization Society, a group dedicated to bringing to the U.S. every bird mentioned in the writing of William Shakespeare. Mute swans were introduced in North America in the 1800s as ornaments for the ponds in parks and zoo, and on the estates of wealthy homeowners.

Most non-indigenous insects usually sneak in without us knowing. The European gypsy moth is an exception. In the 1860s, E. Leopold Trouvelot, with dollar signs in his eyes, imported the moths from France hoping to produce a more disease-resistant silkworm and establish a U.S.-based silk industry. Some escaped, of course, and quickly set about populating the northeastern part of the U.S., leaving in their wake completely defoliated swaths of forest. In just more than a century, they have reached as far as Wisconsin to the west and Virginia to the South. Millions of dollars have been spent on efforts to control the moth’s spread. No specific study has calculated the economic impact of the gypsy moth alone, but a 2011 study titled “Economic Impacts of Non-Native Forest Insects in the Continental United States,” published in the online journal PLoS ONE, says that insects that feed on foliage, like the gypsy moth, cause $868 million in annual damages across the United States.

All of these animals have upset the balance of the foodweb and ecosystems of our local area, but if you were going to award a prize for the most successful invasion, it would have to go to the plant world. The Pennsylvania Department of Conservation and Natural Resources has cataloged 110 herbs, flowering plants, grasses, shrubs, and trees that have invaded the commonwealth and have the potential to make nuisances of themselves. Some already have.

Oriental bittersweet and Japanese honeysuckle, fast growing, voracious vines, have smothered acres of native trees and shrubs, particularly at Presque Isle State Park.

Another invader, garlic mustard, is a small but prolific plant that quickly spreads across the forest floor, displacing native plant life. Its success is aided by white-tailed deer, which consume the native plants they are adapted to eat, leaving only the garlic mustard behind.

It is a particularly troublesome plant and provides a good example of how even small changes in an ecosystem can radically alter the landscape. Garlic mustard looks enough like toothwort, the preferred host plant of the West Virginia white, a native butterfly that will lay its eggs on the plant. The garlic mustard is toxic to the caterpillars of this species, however, so when they hatch and begin eating, they die. Further, garlic mustard contains chemicals that affect mychorrhizal fungi associated with native trees, resulting in suppression of native tree seedling growth.

The results affect not only the threatened West Virginia white butterfly and native trees, but also the songbirds that come to our area every spring. Migrating songbirds time their migration to coincide with the caterpillar hatch, as larvae are their preferred food source. With fewer caterpillars available, it takes longer for birds, like warblers, to fatten up for the next leg of the journey, or they continue on with not enough fat stores, putting them at risk of death during the arduous migration.

Matt Pluta, Program Manager for Environment Erie and coordinator of the Weed Warrior project at Presque Isle, says that it’s important to remove as much garlic mustard as possible, especially before it goes to seed. “The Weed Warrior volunteers have been doing an exceptional job of removing garlic mustard over the past three years, but we still have a long way to go. It’s very prolific.”

Common Reed (or phragmite) is even more badly behaved. This tall, plumed grass has overwhelmed many ponds and wetlands at Presque Isle, crowding out all native plants and making it impossible for waterfowl, shorebirds, and other water-related animals to feed or utilize the water the way they typically would. They spread by underground rhizomes and seeds making their advance every growing season a challenge to park officials hoping to slow its growth or eliminate it along with other invaders, like Japanese knotweed, shrub honeysuckle, and purple loosestrife, which are gaining “rootholds” in every corner of the park.

According to Holly Best, Assistant Park Manager, it is Great Lakes Restoration Initiative grants that have improved their ability to battle invasive plants more effectively. “This funding has provided us with supplies, equipment, and personnel to do a lot of work toward removing invasive vegetation on the park. This will be a continual battle to maintain what we have done, as well as continue to treat additional areas. We hope to receive funding in the future to support this program for many years.”

Unfortunately, more invaders are knocking on our door.

The emerald ash borer and the Asian longhorn beetle, both insects native to Asia have been reported nearby. They are believed to have arrived in the U.S. in wooden crates or packing materials. Both threaten a variety of native trees and have spurred the campaign to discourage people from transporting firewood out of home territories. According to a study done by the Forest Service of the US Department of Agriculture, Erie County is at risk of receiving the longhorn beetle via wood waste from the New York City area that is transported to the Lakeview landfill in Summit Township.

The hemlock woolly adelgid, also a native to Asia and related to aphids, was introduced via plants imported to the United States for the nursery trade in the early 1950s. Last year, it was reported as close as Cook Forest State Park near Clarion. These insects can decimate a hemlock tree within just four years after infestation. Thankfully, recent reports suggest that our very cold winter may have killed them off in some regions, giving foresters and biologists time to plan more defensive strategies.

The biggest potential invader to the Great Lakes looming on the near horizon, however, is one that could have a significant and quite noticeable effect in the waters of Lake Erie.

The Asian carp, the umbrella term for a group of large fish that comprises the bighead, silver, and black carp species, were originally introduced into the U.S. in the 1970s as weed and algae controllers in aquaculture and wastewater treatment plants. They have since migrated through the Mississippi River system and into the Missouri and Illinois rivers. The carp are now threatening to enter the Great Lakes through the artificial Chicago Area Waterway System (CAWS) that links the Illinois River with Lake Michigan.

As with any other aquatic invader, these carp threaten to crowd out native fish and occupy their breeding habitat, and compete with native fish for food. They can grow to more than 100 pounds and five feet in length. If successful, they have the potential to ruin the $7 billion Great Lakes fishing industry and disrupt the region’s $16 billion recreational boating industry. The silver carp poses the most danger to humans because these easily startled fish can jump eight to ten feet into the air; causing human injuries, including cuts, black eyes, bruises, and concussions.

Three bighead carp have already been found in Lake Erie; two in Ottawa County, Ohio and one in Ontario, Canada. Fortunately for now, these are believed to be isolated incidents and there is no evidence of a breeding population.

Interested stakeholders in both the U.S. and Canada are working diligently to prevent this invasion. Last year, the Obama administration released an upgrade to their control strategy framework for Asian carp control, including new physical and chemical control tools, strengthening the electric barrier system in the CAWS, and constructing a new project to completely separate the Great Lakes from the Mississippi basin near Fort Wayne, Ind.

Fishing and conservation groups such as the S.O.N.S. of Lake Erie are watching carefully. Jerry Skrypzak, President of S.O.N.S., says, “the carp can cause more problems than we already have with invasive species. If the Lake Erie hatchery crashes, we could lose the entire fishing industry. If the carp are allowed to enter the Great Lakes and successfully breed, we really don’t have any idea what will happen in the long run. It could be a disaster.”

What is clear is that with increasing global trade, the Asian carp are not the last invasive species with which we will do battle. But this moment — before the carp have successfully invaded — is our first chance to prevent an aggressive species from entering our ecosystem rather than deal with the consequences. Prevention, despite its high price tag, is far more economical and less damaging to the environment than cleaning up afterwards like we are still doing today with the gypsy moth.

The Great Lakes and Mississippi River Interbasin Study Report submitted to Congress earlier this year by the U.S. Army Corp of Engineers suggests that developing infrastructure to keep Asian carp out of the Great Lakes could take decades and cost $15 billion or more. And we've already spent approximately $26 billion trying to rid ourselves of the gypsy moth and other non-native foliage-eating insects in just the past three decades.

This undertaking to stop the carp also suggests that we are learning to be more careful of what we deliberately bring into our water and onto to our land, or being more mindful when first discovering a non-native species in our midst. That’s a start.

While we wait for federal and state authorities to execute a plan to address the potential Asian carp invasion, what can the average citizen do? It often seems like nothing we, as individuals, do can make a difference. 

But that would be wrong.

If you are a boater, you can make sure your ballast is empty before moving your boat from one watershed to another, preventing, perhaps, the introduction of zebra mussels to a new watercourse.

If you are a gardener, you can educate yourself about the non-native plants you may have growing in your landscape and replace them with native plants that are designed to support native wildlife and thrive in local conditions, to boot.

And if you camp, leave local firewood at home and source your campfire wood from the area where you are staying, which prevents the spread of wood-borne insects to new areas.

It never seems like enough, but small efforts, practiced by many can make a difference. If you have no interest in protecting native species or habitat, or if taking a few extra steps seems like just too much trouble, remember that, according to the last study done in 2003 by the Erie Chamber and Growth Partnership, Erie’s sport fishing industry generated $9.5 million annually for the county, and produced 219 fishing-related jobs.

If Asian carp move in, all of our pocketbooks may be a little emptier.

Mary Birdsong can be contacted at, and you can follow her on Twitter @Mary_Birdsong. 

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