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Backpacker Magazine – December 1999

America's Least Wanted Flowers

There's a reason why your field guide doesn't list some flowers: they're not supposed to be there.

by: Thom Hogan


I was walking with a friend on the Bay Area Ridge Trail recently when we came upon a patch of bright yellow flowers in bloom at the side of the trail. This was the largest, fullest display of wildflowers we'd encountered, so I started to get out my camera. My friend, who regularly hikes the area, stopped me. "Don't bother, that plant doesn't belong here," he said.

Welcome to the world of invasive plants.

Every day in America, almost 5,000 acres of wildlife habitat are invaded by alien plants. To put that in perspective, that's an area the size of Yellowstone National Park losing a piece of its natural plant community every 14 months. Imported plants often wipe out more fragile native ones, even when actions are taken to stop the process. The result is that unique plants disappear and the ecosystem becomes less complex, more monotonous. Worse still, endemic animals and plant life dependent upon the displaced native plants have to adapt to the changes, move on, or die.

At every hiking locale I've visited lately, I've asked a land manager if there are any alien or invasive plants in their jurisdiction. In Washington, Idaho, Utah, California, Alaska, Montana, Wyoming, Pennsylvania, and New York, I've gotten an earful. Clearly we're nearing a critical point. If we don't get rid of America's Least Wanted now, the lands we hike may never be truly native again.

Most invasive plants are characterized as "aggressive." This can mean they put down extensive root systems, seed often and prodigiously, use nutrients in high quantities, or grow in ways that reduce sunlight and water access to other plants. While winds can blow plant seeds long distances, most invasions result from the acts of man. As the population has shifted to the South and West in recent decades, some people have taken their favorite plants with them. Jet transportation has made global travel and shipping more pervasive, making the accidental and deliberate transfer of foreign plants from continent to continent easier.

"On a geological scale, we are recreating a global Pangaea, where invasive species will come to occupy their maximum potential ecological range," said Randy G. Westbrooks, station leader of the Whiteville Noxious Weed Station (USDA), North Carolina, at a recent conference on the subject. "In the process, many highly desirable and functional species are likely to be displaced or eliminated altogether."

Many non-native plants now found in the backcountry, like purple loosestrife (lythrum

salicaria) and spotted knapweed (centaurea maculosa), are classified as having "little or no value to wildlife." The plants they displace, on the other hand, often are primary food sources for wild animals.

There are relatively few studies describing how alien plants impact wildlife, but one published on the knapweed crisis in Montana should be enough to sound the alarm. Elk don't eat spotted knapweed, currently the most problematic and pervasive backcountry invasive plant in the state. In areas where knapweed doesn't grow, the study found the presence of elk, as indicated by high pellet counts of 1,575 per acre. Where knapweed was present (even in places where other edible grasses also grew), researchers found only 35 pellets per acre. Knapweed has now spread from the ranches into the wild backcountry in Montana, and elk migrate away from it. Which would you rather see, native wild elk herds where they belong or fields of this alien flower where they don't? Worse still, knapweed-covered sites have a higher evidence of erosion, so it's not just wildlife that is being displaced.

The Bureau of Land Management estimates that on the lands it manages, plants not native to the habitat have taken over 6 million acres in the last 15 years. The National Park Service spends more than $2 million a year on the problem and estimates that this is only 10 percent of the money needed to control invasive plants. Even President Clinton has gotten involved: In April he signed the Invasive Species Executive Order, which directs all the land agencies to monitor, research, and act on alien plant issues. Secretary of the Interior Bruce Babbitt put it this way: "The invasion of noxious weeds has created a level of destruction to America's environment and economy that is matched only by the damage caused by floods, earthquakes, wildfire, hurricanes, and mud slides."

Hikers are a small part of this very big problem. Our biggest impact comes in disrupting soil. There are also a few documented cases of accidental transportation (carrying seeds in boot treads or clothing, for example). Further, anything we do to disrupt fragile native plant life--pitching a tent in a flower-filled high meadow, stepping on plants by hiking off-trail, disposing of wastes carelessly--helps more aggressive plants displace native species.

Backpacker is taking action on this problem, donating time, money, and resources to organizations like the Student Conservation Alliance that have active programs designed to eradicate non-native plants in the backcountry. And we'll continue to report online and in Signpost as we learn of specific non-native plant infestations that you can help control. In the meantime, there are other things you can, and should, do:

  • Ask the land manager where you hike if there are any invasive plants in the area and if there's anything you can do to help. Backpacker plans to sponsor at least one trial eradication program that provides plant cards to help backcountry hikers identify and dispose of such plants. (Note: In some places, a plant belonging to a particular species can be uprooted and left; in others, the plant must be put in a bag and removed. Make sure you get clear, accurate instructions before doing anything).

  • Do not disturb the ground where you hike. The reason you plow the soil before planting your garden is the same reason you should avoid doing anything like that in the backcountry. Disturbed soil allows new plant life to take hold. When you pull up your tent stakes, pack the soil back into place.

  • Stick to the trails. When you walk through wild fields, you increase the chances of unintentionally becoming a seed carrier. Check your cuffs and boots after walking through fields, and remove anything you've picked up there before moving on.

  • Come to the trailhead clean. Inspect your boots and vehicle tires after your trip because large numbers of seeds are transported by wedging themselves into the treads. I checked my boots with a magnifying glass after my last hike, and, sure enough, I found at least two seeds in a bit of caked-on mud. Also, examine your pack pockets and compartments for plant debris.

  • Never take seeds or samples of a plant from one area and transfer them to another. I've known people who've gone hiking, encountered a plant they like, taken a slip or seed, and transported it hundreds of miles to their home, where they replant it. When you take plants from their native habitat to a new one, you risk spreading aggressive plants that will displace nonaggressive ones.

  • Use only local plants in your garden, and ask your nursery what guidelines it follows to avoid selling alien plants. If you live close to wildlands, this is extremely important, as pollination patterns and winds have a habit of expanding a flora's territory far beyond your yard.

With your help, we can control America's Least Wanted.



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