Creatures Of Habitat. Mark Hengesbaugh. Published by Utah State University Press. For additional information about this book

Transcription

1 Creatures Of Habitat Mark Hengesbaugh Published by Utah State University Press Hengesbaugh, Mark. Creatures Of Habitat: The Changing Nature of Wildlife and Wild Places in Utah and the Intermountain West. Logan: Utah State University Press, Project MUSE., For additional information about this book Accessed 29 Apr :18 GMT

2 CHAPTER SEVEN Aliens have invaded! Weeds take over habitat. Wherever people live, work, or play, weeds follow like a dark shadow. When we visit natural areas to hike, bike, or take a Sunday drive, seeds of these alien travelers stowaway on us and invade our complex, yet balanced native ecosystems. These exotic hitchhikers root and spread quickly wherever humans have disturbed natural landscapes places like roadsides, trailheads, and cow-pounded pasture. When this happens, a single variety of scrappy foreign plant will overrun many types of native plants and the resulting weed field is either inedible or poisonous to wildlife. Consequently, weeds have become a major cause of habitat loss in the West. For example: A 1988 study in Glacier National Park found that invading weeds wiped out 6 of 21 of the park s native plant species in the rare category. Weeds have taken over important winter grazing areas in Montana and Wyoming, reducing elk and other wildlife populations, says Steve Burningham, a weed specialist with the Utah Agriculture Department. Whole ranches in Washington and North and South Dakota have been overrun by a weed called leafy spurge, forcing the owners to sell out, reports Larry O. Maxfield, Utah s Bureau of Land Management Weed Coordinator. Ranchers, hunters, and conservationists all agree weeds must be controlled, yet the rate of infestation is snowballing. At least nine million acres of BLM land that s the size of four Yellowstones already have a serious 95

3 Weed-infested scenic area. ALAN HUESTIS / FAST FOCUS PRODUCTIONS weed problem, and officials predicted the trouble would spread to a total of 19 million acres by On all Western public lands, weeds are spreading at a rate of seven square miles a day. It s important to remember that the plants we call weeds are not pests in their native land, Maxfield points out. Where these robust plants evolved, natural predators, such as specialized bugs and diseases, keep them in check. For example, in China they spray insecticides on their native Asian tamarisk plants to kill the bugs that eat them. In Utah, where the nonnative Asian tamarisk has gotten loose, it encounters no such opposition as it overruns the state s riversides. We have to spray herbicides to kill Asian tamarisk because it has no native predators in Utah. Without natural enemies, weeds quickly dominate natural areas, outcompeting the native plants for light and nutrients. They tolerate a broad range of climatic conditions and, once established, are tough to eliminate. Weeds reproduce abundantly; one yellowstar thistle plant, for example, produces 96 CREATURES OF HABITAT

4 150,000 seeds. Wildlife can t eat weeds and some like knapweed are poisonous. In this way, weeds quickly turn a diverse, stable, native ecosystem into a near monoculture of exotic pests. Utah s BLM office lists 17 weeds as noxious or dangerous. Of these, four are thistles and four are knapweeds. Some of them will fool you. Lots of people see northern Utah hillsides covered with yellow flowers and think they re really pretty, says Maxfield. They don t know they re looking at an infestation of dyer s woad, a scrappy invader from Europe that takes over and won t go away. Weeds arrive here from other continents, often brought intentionally as ornamental plants or accidentally along with livestock feed. Once here, they take us for a ride. Weed seeds stick to our shoes, clothes, tires, fenders, and domestic animals. They hitchhike on us, going where we go, sprouting wherever we seriously disturb the native vegetation. Road building is a prime invasion pathway for weeds. A bulldozer s blade clears off native plant cover that would normally resist weedy intruders. The weeds are then free to sprout and spread on bare roadsides, and they quickly invade natural areas on either side. Humans build the roads, then disperse the weed seeds along them. It s an efficient system for the weeds. So effective that introduced plants now form the dominant cover on many... landscapes in western North America and are widespread in Utah, according to local scientists in their paper Selecting Wilderness Areas to Conserve Utah s Biological Diversity. These local scientists argue that it s cheap and effective land management to keep native ecosystems in one piece rather than allow them to be cut up with roads and then fight the resulting problems of weeds and loss of native plants. Once weeds are established, there are several strategies to get rid of them; no one of them is completely satisfactory. Weeds on a one- or twoyear life cycle, like thistle, can be yanked. These are annual or biannual plants, sprouting from seed. The hand-pulling technique worked well for Millard County, which held an annual Weed Day where hundreds of volunteers would pull scotch thistle out of wild areas. After a few years, Weed Day had to relocate for lack of weeds. Perennial weeds such as knapweed and dyer s woad have a taproot that can drill a dozen feet into the ground. If you yank the top of one of these plants, it will just grow back from the root. In these cases, chemicals are the weapon of choice. Herbicides are still the main tool to control perennial 97

5 weeds, says Burningham. But biological control is our only hope in some places like wild and pristine areas, where you don t want to use chemicals. Biological weapons, such as bugs that prey on weeds, are moving from the laboratory onto the range. Local land managers report they have introduced thistle head weevils into musk thistle infestations. This specialized insect bores into the thistle s seed head and destroys seeds. But weed colonies have more lives than cats. With any weed-fighting strategy, people must go back to where the intruders are established and kill them year after year. For this reason, the most effective and highest priority technique of weed management is prevention, says the BLM. On 95 percent of BLM land, they point out, weeds are not yet a serious problem. In the big picture, the most elegant strategy to keep natural landscapes weed free is to stop building new roads into them. But there are important ways hikers and mountain bikers can help the problem as well. Land managers ask recreationists to clean their boots, bikes, pets, and cars before heading into natural areas. For outfitters, it s the law that any feed for pack animals must be certified weed free. If you see thistle plants, yank them. If they re flowering or gone to seed, bag them and burn them at home. Report weed infestations you see in the backcountry to local land managers. These alien invaders are merciless take no prisoners. 98 CREATURES OF HABITAT