198 



SEPTEMBER 

 1993 



OFFICE OF TECHNOLOGY ASSESSMENT ■ U.S. CONGRESS 



REPORT brief 



The Nation 

 can 

 further 

 cut the 

 costly 

 effects of 

 non- 

 indigenous 

 species 



armful non-indigenous species (NTS) — those 

 plants, animals, and microbes that are found 

 beyond their natural geographical range — 

 annually cost the Nation millions to billions 

 of dollars and cause significant and growing 

 environmental problems, says a new report 

 from the Office of Technology Assessment, 

 Harmful Non-Indigenous Species in the United 

 States. At the same time, beneficial MIS form 

 the backbone of American agriculture and are 

 important in horticulture, fish and wildlife 

 management, biological control, and the pet 

 industry. OTA's work takes a comprehensive 

 look at the damaging species. 



WHAT'S WHERE 



The movement of plants, animals, and mi- 

 crobes is much like biological roulette. Once 

 in a new environment, an 

 organism may die. Or it 

 may take hold and repro- 

 duce with little noticeable 

 effect. But sometimes a 

 new species spreads, with 

 devastating results. 



Almost every part of the 

 country faces at least one 

 highly damaging NIS — 

 like the zebra mussel, 

 gypsy moth, or leafy spurge 

 (a weed). They affect many 

 national interests: agricul- 

 ture, industry, the protec- 

 tion of natural areas, and human health. The 

 melaleuca tree, for example, is rapidly de- 

 grading the Florida Everglades system by 

 replacing sawgrass marshes, forests, and other 

 natural habitats with single species stands. In 

 Hawaii, NIS are responsible for extinctions 



and replacements of indigenous species; they 

 now make up at least one-half of the State's 

 wild plants and animals. 



Naturally occurring movements of species 

 into the United States are rare. Most organ- 

 isms arrive with human help. Numerous NIS 

 entered the country as unintended contami- 

 nants of commodities, packing materials, ship- 

 ping containers, or ships' ballast. Others were 

 intentionally imported as crops, ornamental 

 plants, livestock, pets, or aquaculture spe- 

 cies — and later escaped. For example, at least 

 36 of the West's 300 weeds escaped from 

 horticulture or agriculture. A number of NIS 

 were imported to improve soil conservation, 

 fishing and hunting, or biological control but 

 caused unexpected harm. 



THE GOOD, THE BAD, 

 THE 'WHO KNOWS?" 

 Some NIS (like soybeans 

 and most pets) are clearly 

 beneficial; some (like 

 gypsy moths, Russian 

 wheat aphids, and crab- 

 grass) are clearly harmful. 

 Some are both, depending 

 on location. And value is 

 in the eye of the beholder. 

 Purple loosestrife, for ex- 

 ample, is an attractive 

 garden plant and a major 

 wetland weed. 

 At least 4,500 NIS of foreign origin have 

 established free-living populations in the 

 United States, a much larger number than 

 were present 100 years ago Approximately 

 15% of the total species trigger severe harm. 

 Most species' economic impact is not 



