A call to arms: The war against invasive species

By Ben Ikenson
Brown Tree Snake
They're Here
From 1950s sci-fi flicks to the more recent Signs, our cinematic tradition reveals that the fear of extraterrestrial invasion has long occupied human consciousness. It is disconcerting to consider menacing life forms taking up residence on our planet and destroying the world as we know it or, worse, removing us entirely.
More disturbing, however, is the fact that "they" are already here, methodically striking away at the biological diversity of the planet. Thankfully, humans may not be first on the chopping block, but we too rely on the intricate web of ecology — just as the rising number of casualty species do. That web is being eaten away, not by extraterrestrials, but by the global spread of noxious invasive species: plants and animals who threaten the health of our landscapes on a scale of epic proportion. "Invasive species and their environmental damage are the most irreversible form of pollution," wrote David Lodge, chair of the National Invasive Species Advisory Committee and an ecology and biology professor at University of Notre Dame.
Cornell University reports that exotic plants and animals on land and water cost the United States up to $138 billion annually, impacting human health, commercial activities, community infrastructures, natural resources, and agriculture production.
The Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW) reports that between 200 and 250 invasive plant species are recognized as major problems in world agriculture.
As the cost and casualties have been steadily climbing in recent years, this silent invasion has alarmed scientists worldwide and has prompted federal agencies to work together to address the problem.
One reason the problem of invasive species is so widespread is the way they spread, grow, and adapt. Since the beginning of civilization, humans — like birds, animals, the wind, evolution, and other forces in nature — have enabled the spread of plants and animals. But the scope of our influence has never been as wide as it is today, and it has expanded exponentially in just the last century.
During American pioneer times, by contrast, exotic seeds traveled slowly and deliberately across the continent as freight in covered wagons, to be planted as decorative flora or as cost-efficient forage for livestock. Today, nonnative seeds can crisscross the country at 75 miles per hour, nested in muddy tire tracks, and can reestablish themselves at the next interstate rest stop. Nonnative species can be transferred inadvertently in freight shipments or carried in ballast water from overseas.
Ironically, an aggregation of diverse species, when misplaced, threatens biological diversity by thwarting native ecosystems. Nonnative plants have a tendency to monopolize landscapes because, in these new territories, they have distinct advantages over the indigenous plants. Freed from the diseases, insects, and other controls found in their native habitats, they use their energy to grow larger and faster, put down deeper roots, and produce more seeds. Uncontrolled, they quickly out-compete and replace native plants. Likewise, displaced animal species frequently outpace indigenous wildlife populations once freed from their native controls.

A Global Epidemic
While most species do not pose threats, the fraction that does is wreaking havoc throughout the United States. In the nation's capitol last summer, a serial sniper shared headlines with the Chinese snakehead, a product of the live fish market at smaller grocery stores that was released into a Maryland pond.
"Snakeheads are voracious predators and eat anything in their path," said Ken Burton, spokesperson for the U.S. Fish and Wildlife Service. They have the capacity to dramatically alter any ecosystem they inhabit. "They also have the ability to move across land and live out of water for up to three days," he said. "They reproduce quickly and in great numbers. The fear was that, under the right circumstances, they could move under their own power across a soggy landscape and enter the nearest tributary, and that would have caused serious consequences," said Burton. "Once an invasive species is 'in the wild,' eradication becomes virtually impossible."
Fortunately, the snakeheads in Maryland didn't do appreciable damage because they were contained in a large pond that was not connected to any other body of water. Other situations have less fortunate outcomes.
In 1962, Rachel Carson wrote Silent Spring as a warning against the use of harmful pesticides and their impacts on birds. Little could she anticipate then that the dreaded absence of birdsong could be caused by the invasive species phenomena. But the invasion of brown tree snakes in Guam has silenced almost every single bird on the tiny island.
In the Southwestern United States, salt cedar and Russian olive spread over riverbanks to the detriment of native cottonwoods and willows and the species who depend on them. Many of the salt cedar were planted decades ago to stabilize streambanks; the Russian olive is still promoted and sold as an ornamental tree.
Similarly, giant salvinia was introduced from Brazil as an ornamental plant for the water garden trade. Now, it's found in all southern states except New Mexico.
"It may have once been pretty in an aquarium," said Steve Williams, director of the U.S. Fish and Wildlife Service, "but giant salvinia is now causing real problems to the health of many regional waterways and the species that depend on them. It's been called an aquatic kudzu," he said. "It blankets an entire pond in days, choking everything underneath, trapping and drowning mammals that try to walk on what looks like a field. Ducks can't land on it. And if your business depends on free, open water, forget it. You can see then how such a presence is attended by both ecological and economic impacts."

Search and Destroy
Responding rapidly to control invasive species is an obvious prerequisite in the battle against these ecological invaders. For some land managers, this is a huge and relentless task.
Before taking a job as an invasive species biologist for National Wildlife Refuges in Oklahoma and north Texas, Dan Dinkler managed the 3,000-acre Maxwell National Wildlife Refuge in northeastern New Mexico. Here, sandhill cranes sail gracefully over wide open valleys. Eagles glide above the rolling, windswept prairie searching for prey. Ducks and geese drift across the surface of scattered lakes, which teem with fat-bellied yellow perch. But Dinkler had little time to admire the seemingly picture-perfect scenery. He was on constant alert for the prolific musk thistle, the bull thistle, the hoary cress, and the tenacious and control-resistant Russian knapweed and Canada thistle, unassuming plants who are a growing affront to public wild lands.

Russian knapweed is toxic to livestock.
According to the FICMNEW, 4,600 acres of public wild lands succumb each day to invasive weeds. Much of this land will never be recovered. If these invasions continue unchecked, wildlife populations will decrease proportionately, and some plant species will likely become extinct. Over a number of years on the high plains, several nonnative plants such as Russian thistle and musk thistle have gained a foothold and insinuated themselves on the range. Some plants, such as toadflax, which forms solid stands, do not adequately hold the soil and have therefore increased erosion significantly. Today, wildlife will not forage on most of the nonnative weeds who are invading northern New Mexico. And some of the invaders, such as yellow starthistle and Russian knapweed, are toxic to livestock. When eaten, they can cause a slow, painful death.
Dinkler used global positioning systems and geographic information systems to locate, map, relocate, and monitor weed infestation sites as part of an integrated weed management program. To fight these tenacious invaders, he selected from an arsenal of weaponry and defense tactics including basic hand removal; mechanical cultivation; low impact, selective herbicide applications; and the planting of competitive, "defensive" grasses. Control methods vary according to the species.
"Additionally, while the annual crop of new plants can be controlled, several years of follow-up is necessary to manage each year's crop of new plants that sprout from the abundant seed bed and perennial root systems," warned Dinkler. For example, some musk thistle seeds can survive 15 years, although the majority will emerge within five years.
That is why Dinkler follows the 3:1 rule: For every year you delay controlling an infestation, it will take three years to regain control. "This rule may vary with locations, species, and environmental conditions, but as a general rule of thumb, it demonstrates why it is important to jump on weed problems as early as possible," said Dinkler.
Although it still poses serious management issues at Maxwell National Wildlife Refuge, the weed infestation problem does not begin or end at the refuge boundary. In Colfax County, N.M., the refuge is just one of several entities, including local landowners, in the process of developing a systematic plan of attack on invasive weeds.
"We all share, or will share, the same invasive weeds eventually, so it is vital to get as many land owners and agencies on board as possible," said Dinkler.
Bob Pitman knows the value of involving the public. As a U.S. Fish and Wildlife Service invasive species coordinator with an emphasis on aquatic nuisance species, Pitman's primary target of attack has been the zebra mussel. He has worked on many aspects of the 100th Meridian Initiative — a broad-based, collaborative effort to prevent the westward spread of zebra mussels and other aquatic invasive species across a longitudinal line that slices the country into almost perfect halves, from central Texas to North Dakota, up through Canada.
A native to Eastern Europe and western Asia, zebra mussels were inadvertently introduced into waters near the Great Lakes region in the mid-1980s, possibly through ballast water tanks of commercial ships. Since then, zebra mussels have spread throughout much of the eastern United States. In addition to impacting native mussel populations, the zebra mussels, which can grow in dense clusters, are clogging up industrial and municipal water delivery systems and costing millions of dollars annually. They currently infest the Great Lakes basin, the St. Lawrence Seaway, and much of the Mississippi River drainage system. They have spread up the Arkansas River into eastern Oklahoma.
As of June 2003, zebra mussels have not been detected in any western waters, but the threat is very real. Several zebra-mussel-infested boats have been stopped at California border inspections, and Washington has stopped five boats with zebra mussels attached to them.
"The 100th Meridian strategies are showing progress, but it's difficult to quantify such a broad concept," said Pitman. "One thing is certain, this battle will last for a long time, and everyone has to be committed to the fight. It can't be done alone, and true partnership with all the stakeholders is crucial to prevent zebra mussel spread over the Continental Divide and to the West."

What Individuals Can Do
The strategy of the 100th Meridian Initiative is based on several components, including early monitoring to detect invasions, rapid response through boat surveys and inspections, and the distribution of information and education. Through a National Aquatic Nuisance Species task force, the Service has worked with partners to increase public awareness. To limit the spread of aquatic invasive species like zebra mussels or hydrilla, Stop Aquatic Hitchhikers! was established as a national campaign to target recreational users such as anglers, boaters, waterfowl hunters, and scuba divers. It provides practical ways they can prevent the spread of aquatic invasive species.
"If people are unaware of their potential impacts in transporting aquatic nuisance species, they could create a very expensive problem that costs resource-dependent industries and tax payers millions of dollars," said Pitman.
Bob Pitman and Dan Dinkler are but two resource managers in the fight against nuisance invasive species, a fight that has gone global. The issue is recognized by international committee members of the Convention on International Trade in Endangered Species (CITES) as a biological scourge threatening every single country in the world.
Quite possibly land managers' most powerful weapon of defense against problematic invasive species is publicity. The war against stubborn invasive species will depend on the strength of an informed public.
"While professional resource managers are doing what we can, the battle cannot be fought without increasing public support and awareness," said Dinkler.
Pitman agreed. "To balance the rate at which the human influence has enabled the growing expedience of invasive species and their consequences, everyone should consider themselves as land managers and take steps toward becoming responsible stewards."
While the United States federal government has some jurisdiction over the importation and interstate transportation of plants and animals, states decide what can be sold within their borders. Because of this discrepancy, a consumer is not likely to see tags on plants identifying them as either native or nonnative. That is why it is crucial to know which species should or should not be sold at local nurseries to be planted in local yards. If more customers express interest in environmentally friendly landscaping by demanding more sales of native plants, suppliers will respond in kind.
One promising sign of change is that sustainable development is gaining momentum and currency outside of the wildlife conservation world. Last May, the Mississippi State University Department of Landscape Architecture unveiled its new state-of-the-art teaching and research facility based on the idea of using native and sustainable resources. Some of its engineering plans included an energy-efficient shelter, a water-harvesting system for irrigation and drinking, and provisions to treat sewage using biological systems.
The new facility created a stir in architectural circles, and it was also lauded by Fish and Wildlife Service Director Steve Williams as an example that shows "construction and conservation are not mutually exclusive." He noted that one of the school facility's many great characteristics is that "its surrounding landscape will be managed to remain consistent with the site's natural plant communities and cycles."
Williams went on to cite that nonindigenous species are at least partly responsible for more than 42 percent of the plants and animals currently on the nation's threatened and endangered species list.
"In the long run, the presence of endangered and threatened species is an important indication to our own species," he said. "We should be looking beyond temporary solutions to existing problems."
These invaders are much closer to us then those menacing aliens masked as humans in Invasion of the Body Snatchers. Yet, without keeping noxious invasive species in check — and looking beyond temporary solutions — we become ever more vulnerable to their costly perils. While only cautionary in science fiction, the threat of aliens taking over our planet is unfortunately no less dramatic in reality.
Ben Ikenson is a writer for the U.S. Fish and Wildlife Service who's based in Washington, D.C. He is also a freelance writer. His articles on wildlife conservation have appeared in regional, national, and international magazines, including Américas, Earth Island Journal, Texas Parks and Wildlife magazine, North American Sportsman Magazine, New Mexico Magazine, and American Indian Report.

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Related Links
100th Meridian Initiative
Protect Your Waters
Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW)
U.S. Fish and Wildlife Service — Division of Environmental Quality: Invasive Species
Aquatic Nuisance Species Task Force

Source: Environemental News Network