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Invasive Weeds Pose Major Threat To American Landscape

May 4, 1998
United States Geological Survey
Wrong time, wrong place. Accidentally and on purpose, America is sowing seeds -- literal seeds -- of destruction. These are the conclusions of a soon-to-be-published book examining weeds in the United States.

Wrong time, wrong place. Accidentally and on purpose, America is sowing seeds-- literalseeds -- of destruction. These are the conclusions of a soon-to-be-publishedbook examining weeds in the United States.

"The invasion of noxious weeds has created a level of destruction to America?senvironment and economy that is matched only by the damage caused by floods,earthquakes, wildfire, hurricanes and mudslides,? Secretary of the InteriorBruce Babbitt said. ?This is truly an explosion in slow motion by opportunisticalien species with few if any natural enemies.?

A multi-agency committee on invasive weeds found that the march of non-nativeplants across the American landscape is so pervasive that the unique differencesof regional plant communities are blurring. Their report, "Invasive Plants:Changing the Landscape of America," is a systematic attempt, involving 17partner agencies, to define the seriousness of the problem. The report will beavailable for public distribution this summer.

Invasive non-native plants, the book says, are now considered by some expertsto be the second-most important threat to native species, behind habitatdestruction.

"This fact book will help readers understand the scope and magnitude of theproblem. We hope it will encourage them to act, to help us control the invadersthat are already here and prevent future invasions,? Babbitt continued. ?Peopleare carrying plants or their seeds from the far reaches of the globe into everycorner of our nation to compete with -- often to destroy-- the wonderful varietythat nature once gave us.?

Over the past decade, the report says, devastating impacts from invasive specieshave been reported on every continent except Antarctica. In the United States,introduced invasive plants comprise from 8 to 47 percent of the total flora ofmost states, a figure especially alarming considering a recent report from theInternational Union for the Conservation of Nature documenting that 1 in 8 plant species is globally threatened with extinction.

Invasive plants are those that have been introduced into an environment in whichthey did not evolve. Consequently, the invaders usually have no natural enemiesto limit their reproduction, and thus easily spread, often unchecked. Inaddition, aggressive non-native species often deal a harsh blow to rare species-- about two-thirds of all endangered species are threatened by non-nativespecies, the report said. As the native plant species decline, the animals thatdepend on them for food and habitat may also be jeopardized.

The book was developed by many of the federal agencies and others with weedmanagement responsibilities. These agencies are part of the Federal InteragencyCommittee for the Management of Noxious and Exotic Weeds. In 1994, in responseto the economic and biological threats posed by invasive plants, these agenciesbegan working together to develop biologically sound techniques for managinginvasive plants on federal and private lands. After noting the lack of adequatesurveys and reliable monitoring data for many of these invaders, the interagencycommittee worked with more than 100 outside authorities to publish a nationalstrategy on the management of invasive plants.

Secretary Babbitt called for the implementation of a national strategy forinvasive plant species. "Invasive non-native weeds," he said, "are changing thelandscape of the United States ... coming in as a result of globalization oftransportation and trade, and putting U.S. ecosystems and lands at anincreasingly greater risk of damage due to invaders."

USDA Deputy Secretary Richard Rominger likewise called for a "greater awarenessof the impact of non-native invasive plants on all ecosystems, be theyagricultural or natural areas."

The report calls the threat of invasive weeds "biological pollution" and "asilent green invasion." Thomas Casadevall, acting director of the U.S.Geological Survey, which is responsible for helping develop better methods ofdealing with invasive species, explained that on a plant-by-plant scale theeffects of these plant invaders are often subtle. "It's like metastatic cancer,"he said. "It starts with a single individual or seed and then is carried toother places by people or nature where nodes get established and proliferate,eventually affecting entire ecosystems."

"The human-induced migrations of invasive species now underway around the worldis unprecedented," the report states. Unchecked, it adds, the impact "will be adevastating decline in biodiversity and ever-increasing threats to food andfiber production." In wild landscapes, the book concludes, invasive plants alterplant and animal communities, water-flow regimes and are especially threatening to native plants and animals.

According to a recent Department of the Interior survey, noxious weeds areinvading western wildlands at a rate conservatively estimated to be nearly 5,000acres a day. Pat Shea, director of the Bureau of Land Management, says that,"Western wildlands and deserts are an important part of our biological heritageand need to be protected from invasive non-native species."

But the invasive species problem is not just in the West, as the bookemphasizes. It affects most states and most public lands throughout the country.

National Park Service Director Robert G. Stanton called invasive species one ofthe most significant threats facing the natural and cultural resources of theNational Park System. At least 1.5 million acres of national park lands areseverely infested and need immediate treatment, the book reports. Says Stanton: "Although vast fields of flowering plants may lookattractive to the visitor, many of these plants are actually silent, greeninvaders, slowly destroying the native, living natural heritage the parks aresupposed to preserve."

USDA Forest Service Chief Michael Dombeck said that Forest Service lands are ina similar situation, with non-native invasive plants affecting every habitattype found on National Forest lands. "We need to be paying particular attentionto the east where non-native invasive plants such as kudzu, Japanese honeysuckleand mile-a-minute weed are completely draping forested areas and affectingforest ecosystem health," Dombeck said.

The report's authors blame the increase and spread of invasive plants on anincreasing human population that has led to greater disturbance of the land,increased demand for food and fiber,

overuse of public land for recreation and commercial purposes, increasedinternational travel and globalization of world trade. The problem is compounded, the report adds,because "many introduced plants appear innocuous when first introduced; theseplants then adapt, and, in the absence of their co-evolved predators, explode intheir new environment."

The committee's partners are:

  • Within USDA: The Animal and Plant Health Inspection Service; AgriculturalResearch Service; Forest Service; Agricultural Marketing Service; CooperativeState Research, Education and Extension Service; Natural Resources ConservationService.

  • Within Interior: National Park Service; Fish and Wildlife Service; U.S.Geological Survey; Bureau of Land Management; Bureau of Indian Affairs; andBureau of Reclamation.

  • U.S. Department of Defense and the U.S. Army Corps of Engineers.

  • U.S. Department of Energy.

  • U.S. Department of Transportation, Federal Highway Administration.

  • U.S. Environmental Protection Agency.

NOTE TO EDITORS: Reproducible figures showing a) Weed Losses and Costs in theUnited States, b) Native and Non-native Plants in the United States byState/Region, and c)Weed Losses and Control Costs in Agricultural andNonagricultural Areas in 1994, can be obtained at the USGS Biological ResourcesDivision website at

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United States Geological Survey. "Invasive Weeds Pose Major Threat To American Landscape." ScienceDaily. ScienceDaily, 4 May 1998. <>.
United States Geological Survey. (1998, May 4). Invasive Weeds Pose Major Threat To American Landscape. ScienceDaily. Retrieved May 22, 2017 from
United States Geological Survey. "Invasive Weeds Pose Major Threat To American Landscape." ScienceDaily. (accessed May 22, 2017).