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7/14/2009 5:01:45 PM
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UCREFRP
UCREFRP Catalog Number
7430
Author
Cook, K. J.
Title
Editor
USFW Year
Series
USFW - Doc Type
1991
Copyright Material
YES
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<br />Beyond the obvious damage to <br />agriculture, exotic plants increase the <br />costs of public works. They damage <br />asphalt highways, roads and recreation <br />trails. And they compromise safety by <br />reducing visibility along roads and at <br />intersections. Most tragically, exotic <br />plants degrade the natural environment. <br />Colorado inaugurated a wetland con- <br />servation stamp in 1990 to provide rev- <br />enue for improving waterfowl habitat. <br />The program arrived just in time. <br />"Purple loosestrife is here, .. says Dan <br />Thomoson, "and we'lI no doubt be see- <br />ing more 01 it. .. <br />Thompson spent much of his profes- <br />sional career with the U.S. Fish and <br />Wildlife Service (USFWS) studying the <br />exotic loosestrife. Purple loosestrife <br />resembles our native mints, but it is a <br />European species from a family closely <br />related to the mints. In 1987 the <br />USFWS published "Spread, Impact, <br />and Control of Purple Loosestrife <br />(Lythrum salicaria) in North American <br />Wetlands. " Thompson was the senior <br />author of this comprehensive report. <br />And even in retirement, he continues to <br /> <br />campaign against the plant. <br />"One plant can produce 3 million <br />seeds," says Thompson, who lives in <br />Fort Collins. '~nd worse, muskrats will <br />chew and eat loosestrife. Just an inch- <br />long stem left by a muskrat can take <br />root and start a new plant. " <br />Thompson has seen waterfowl <br />habitat in the East and Midwest deteri- <br />orate badly because of purple loosestrife <br />infestation. Many lawn and garden <br />stores sell purple loosestrife as an <br />ornamental which guarantees the plant <br />wiII eventually establish itself in <br />Colorado's wetlands. In his 1990 book, <br />Colorado Flora' Eastern Slope, William <br />Weber, Colorado's pre-eminent field <br />botanist, indicates the plant is already <br />welI established in some foothills ravines <br />and other lowlands. <br />Other exotic weeds cause other <br />problems. <br />According to Charles Jonkel, profes- <br />sor of wildlife biology at the University <br />of Montana, the various knapweeds <br />threaten the survival of grizzly bears. <br />Knapweeds drive out the native plants <br />that produce the roots, fruits and vege- <br /> <br />tation on which grizzlies depend for <br />gaining 85 percent of their hibernation <br />weight. <br />"The same amount of land won't <br />support as many bears," says Jonkel, <br />"so we'lI lose them. " <br />Grizzly bears may seem distant from <br />Colorado, but the knapweeds are here. <br />Russian knapweed is toxic to horses and <br />other species might be. Left on poor <br />pasture, hungry horses may consume <br />100 much Russian knapweed and sud- <br />denly die soon after symptoms appear. <br />This relative of the sunflower quickly <br />establishes itself in pastureland, yet the <br />average horse owner doesn't know <br />knapweed when he's standing in it. <br />The knapweeds are only a few of the <br />283 exotics among Colorado's 2,000 vas- <br />cular plant species. Other particularly <br />troublesome plants include leafy spurge, <br />Canada thistle, several toad flaxes, many <br />grasses, tamarisk and Russian olive. <br />Leafy spurge makes botanists and <br />weed managers wince. Wildlife mana- <br />gers are having the same reaction as they <br />begin to understand the plant's full <br />implications. <br /> <br /> <br />Tamarisk growing along riverbanks traps silt and narrows river channels. <br /> <br />May/June 1991 <br /> <br />11 <br />
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