WHAT YOU CAN DO:

Talk to local weed control representatives about what weeds are problems in your area and how you can eradicate them from your property.
• When traveling, take time to clean dirt out of your shoes, remove seeds from your socks, and wash your car, boat and fishing gear so you don’t inadvertently transport seeds or animals.
• Use certified weed-free feed for stock.
• Do not release plants, animals, or insects into the wild.
• If you locate an infestation, let the landowner or land management agency know so they can initiate control efforts.
• Use native plants for landscaping.

They come by car, boat, train, and plane. They hitchhike rides in your socks or in the mud trapped in the treads of your shoes. They were imported intentionally to help control erosion and decorate gardens, secretly to ‘improve’ the fishing, or mistakenly as stowaways in the holds of ships transporting cargo to the United States from Europe and Asia. They follow fire, road construction, grazing animals, hiking trails, and new home sites. They are alien invaders—non-native plants, insects, diseases, and animals—and they are taking over the North American landscape.

According to a survey by the U.S. Department of the Interior, noxious weeds quadrupled their range in the United States between 1985 and 1995 and the shocking trend continues unabated. As many as 133 million acres across the nation are infested today. In Wyoming, 1.2 million acres are suffering impacts from exotic species according to estimates, with the prospect of many more as a result of massive amounts of disturbance due to oil and gas development as well as unrelated road building and subdivision expansion.

Invasives don’t just alter the landscape, they also infest the nation’s waters reducing game fish populations; increasing the operating costs of drinking water plants, dams and power plants; degrading recreational boating opportunities; and reducing property values. Stretches of the Madison River in Yellowstone National Park have has many as 500,000 New Zealand mud snails per meter, while Pelican Creek, also in the park, has seen its annual cutthroat spawning run decimated, dropping from 40,000-50,000 fish to none because of the presence of whirling desease.

The effects of these invaders are more than cosmetic. Noxious weeds out-compete food crops lowering yields and raising costs. They also reduce the amount of forage available on rangelands and contribute to the decline of native plants and animals. Meanwhile, the decline in cutthroat populations in Yellowstone threatens the entire food chain as everything from grizzly bears to pelicans and osprey rely on the fish at certain times of the year for their sustenance.

The chief of the United States Forest Service, Dale Bosworth, has identified invasives as one of the four top threats to the health of the nation’s forests. The cost to the national economy for managing invasives has been estimated to be as high as $137 billion per year, and that number is rising as the price of eradicating these plants and animals once they take hold continues to go up.

"I have a long list of problematic invasives found around Lander," says Lars Baker, the supervisor of Fremont County Weed and Pest. "Some of these plants can be quite attractive. Like salt cedar. It’s very pretty… but we may lose thousands of acres of lake out at Boysen Reservoir to salt cedar… and once salt cedar is established, it out-competes native cottonwoods and willows."

Salt cedar, also known as tamarisk or tamarix chinensis, is an attractive shrub with small pink blossoms that came to North America from Asia for use both in erosion control and as a garden ornamental. In its native habitat, salt cedar’s distribution is kept in check by a variety of insects, animals, and diseases. But these controls were not imported with the shrub. Consequently, salt cedar, like other invasives, has no natural predators in North America.

"Salt cedar is just one example," Baker says. "The core of this problem is that plants are brought over without the complex of natural enemies they evolve with. So once here, they get out of control. "Humans do this all the time," Baker continues. "What looks like a good deal turns out to be a bad one. Take smooth brome. We brought it over as a crop, and it is a good crop. Smooth brome is a major component of most hay. But it out-competes native grasses and takes over rangelands. And most wild animals don’t recognize smooth brome as a food source."

Invasive species damage or destroy nearly as many acres of land each year as wild fire. And unlike the impacts of fire, the effects of invasives can be permanent. In the United States, as many as 2,300 acres of BLM land are affected every day, which says nothing about the number of acres affected that are controlled by other public land agencies or private landowners.

Most backyards harbor noxious weeds. In Wyoming, these include knapweeds, mustards, bindweed, crab grass, Russian Olives, cheat grass, and thistles. And of course, there’s also leafy spurge or euphorbia esula, which has reduced the productivity of grazing land in the state by 50 to 75 percent and costs taxpayers and agricultural producers in Wyoming, Montana, and the Dakotas $144 million a year in production losses and control expenses.

Invasives like leafy spurge can be admirable. They are tenacious, opportunistic, and in many cases, beautiful. People who work to eradicate invasives often develop a grudging respect for the plants they are battling.

"I’ve come to admire this plant," Keith Fletcher, a landscape conservationist who is fighting to eradicate leafy spurge for the Nature Conservancy in Iowa admitted in a recent Conservancy newsletter.

"Leafy spurge has buds in the roots. If you pull the plant up, if you mow it, if you burn it, if you take a disk and cut it up into one inch pieces, the buds are stimulated to make new plants. And if you don’t mow the spurge, it makes new seeds and shoots them 15 feet. It is like something out of Star Trek."

These kind of adaptations are what make invasives so devastating to the ecosystems they infest. New Zealand mud snails reproduce asexually. A single snail the size of a pepper flake can grow and then replicate itself to populate a stream with upward of 700,000 snails per square meter.

SINKS CANYON

Sinks Canyon outside of Lander represents a microcosm of the challenges facing land managers in their battle against invasive weeds. Over the past three years, the south-facing slopes of the canyon have become blanketed in a purplish-brown cloak of cheat grass. The change is dramatic.

The proliferation of cheat grass followed in the wake of prescribed burns done in the canyon by the forest service to push back juniper trees and improve bighorn sheep habitat. Unfortunately, the burns seem to have had the opposite effect. The juniper has been pushed back, but the forage that replaced them has little value for herbivores.

"We’re very concerned about what we are seeing in Sinks Canyon," says Karl Brauneis, a forester with the Shoshone National Forest. "Up until two years ago, we were getting good results from our prescribed burns in the canyon, but with drought and global warming, the invasives are out- competing the natives. Cheat grass is proliferating all along the Lander faces.

"I really question whether we will do prescribed burns at low elevation sites in the future as we continue to experience drought," Brauneis adds. "We’ll probably make some major changes to our management practices in the future."

Cheat grass, which has replaced whole ecosystems in Utah and Nevada, was once thought to be unable to flourish in Wyoming because of the state’s cold temperatures. That seems to be changing with warming temperatures and prolonged drought. Moisture and fire suppression could help native grasses out-compete the cheat grass, but Brauneis is not optimistic Wyoming is going to get out of its drought cycle. In the meantime, he fears animals like mule deer and bighorn sheep will suffer from the loss of forage in the canyon.

Once invasives are established, native plants and animals often have no chance. Their water supplies are sucked up by thirsty invaders. They are deprived of vital nutrients and crowded out by their new neighbors. Soils are poisoned by biological toxins secreted by the aggressive newcomers. As natives are replaced, the other animals and insects that relied upon them for shelter and food are displaced, and the entire food web is disrupted.

"Prevention is the best tool against invasives," Baker says. But in many areas, he concedes, it is too late.

"The seeds of field bindweed (a small morning glory vine) have an 80-year dormancy," Baker says. "Once you have field bindweed in your yard, you have it forever… We’re never going to eradicate these plants. The question is: How do we learn to live with them?"

Baker advocates what he calls integrated weed management that involves everything from chemicals and biological controls, to modified irrigation techniques, prescribed burns, specific mowing patterns, and crop management. In Yellowstone National Park, the park service is aggressively over-fishing lake trout in Yellowstone Lake in an attempt to keep their numbers down. Anglers are required to kill any lake trout they catch.

Almost all control techniques have critics. With plants, only hand weeding is risk free. But hand weeding is expensive, time consuming, and ultimately ineffective against the onslaught of noxious weeds. Herbicides have been used for decades with some success, but plants are building up tolerance to the chemicals. Furthermore, many people are concerned about the poisoning effect on the land, on people, and on other plants and animals.

Biological control, which entails introducing predators targeted toward invasives, can also be controversial. On the surface it appears counterintuitive to be bringing in more new species to try to get rid of others. The track record for this strategy is not particularly good.

"Biological controls were used to control musk thistles several years ago," Baker says. "Unfortunately the beetles that ate the musk thistle also ate native thistles. At the time, any thistle was considered a nuisance but that has changed. Some of the native thistles are now threatened or endangered." Baker is more confident about the biological controls currently being used for leafy spurge. Tests have shown that the beetles do not move to other native plants once the leafy spurge has been eradicated. They also appear to leave a native spurge, euphorbia robusta, alone.

But only time will tell. In the meantime, the fight to keep out invasives is a fight to keep America’s landscape diverse and bountiful. Each infestation of a non-native species is akin to another strip of fast food restaurants homogenizing the cities of America.