MIAMI — The relentless Australian melaleuca tree is spreading through Florida's wetlands at the rate of 50 acres a day, and the giant African snail is running wild. California's Clear Lake is awash in so many exotic fish that the tule perch can barely breathe.
And in Hawaii the brown tree snake has both scientists and the tourism industry terrified. "The possibility of this snake becoming established in Hawaii presents a nightmare scenario," said biologist Thomas H. Fritts, an expert on the reptile, a nocturnal climber from the South Pacific that can grow to eight feet long and can slip into homes through the plumbing.
Although dramatic, these are just a few examples from a list of 4,500 foreign species that have taken root in the United States, many of which are crowding out native species and causing devastating ecological and economic consequences.
Moreover, the adaptability of several aggressive plants threatens to create a biological sameness to diverse areas of the country.
"In Hawaii, I saw all the plants I see here--melaleuca, Brazilian pepper, the hibiscus tree," said Dan Austin, a professor at Florida Atlantic University and a member of Florida's Exotic Pest Plan Council. "They dominate the local landscape."
The impact of foreign invaders is detailed in a newly released 390-page report from Congress' Office of Technology Assessment, which concludes that the spread of harmful exotics such as the kudzu vine, gypsy moth and the zebra mussel far outstrips efforts at control. The cost to agriculture, industry and human health runs into the billions of dollars, the report says.
"There is no national policy on the introduction of exotics," said Phyllis N. Windle, a biologist who directed the three-year OTA study.
"The problem is so diverse, and the country is so big and with these non-indigenous species, we've been far too lax."
Every region of the United States--indeed, every state--is affected, as are several national parks. Among those especially imperiled are Yosemite, which is troubled by several plants including a non-indigenous thistle; the Great Smoky Mountains, which have serious problems with wild hogs, and Canyonlands, which is plagued by the salt cedar tree.
Described in the OTA report is a rogues' gallery of foreign pests, some were intentionally introduced, some were escapees from captivity and others got to this country as stowaways. The Asian clam, which covers huge areas of San Francisco Bay, came in with ships' ballast water, for example.
After sneaking into the United States in shipments of used tires in 1985, the Asian tiger mosquito has spread to 22 states. The kudzu vine, planted for erosion control, now covers the southeastern United States like the dew. A few released pets quickly gave birth to flocks of monk parakeets in Florida. And the dangerous African honey bees simply flew across the Mexican border.
As a gauge of just how serious the problems are, the OTA report estimates that just 15 foreign species of plants, insects and disease-causing organisms now established in the United States could cause as much as $134 billion in losses over the next 50 years.
Almost two months after the OTA report was presented to the House Merchant Marine and Fisheries Committee, Windle said, Interior Secretary Bruce Babbitt and several members of Congress have taken an interest. "I see concern moving from the specialists, who are quite alarmed, to the public and policy-makers," she said.
But no one expects a quick response. Earlier this year, 25 of the country's top scientists, including Stanford's Paul Ehrlich and zoologist Edward O. Wilson of Harvard, signed a letter to Vice President Al Gore, warning that the integrity of the nation's natural ecosystem is "severely threatened by invasions of alien species." The scientists urged the Clinton Administration to come up with a national program to deal with the problem.
"It seems like nobody cares," said Fritts of the National Biological Survey in Washington. "It's like, what if they gave an environmental disaster and nobody came? Well, that's what's going on."
Not all foreign species of plants and animals are unwanted. Wheat, soybeans and cattle, the foundation of U.S. agriculture, were all brought to North America from elsewhere. Many other exotics cause no harm.
But approximately 15% of all exotic plants and animals do cause severe economic, environmental and health damage, the report estimates.
California has its problems with exotics, including the Asian clam, the African clawed frog, wild rabbits in Channel Islands National Park, the stickleback fish and a host of insects and fungi, all of which cause massive economic and environmental losses. Another outbreak of the Mediterranean fruit fly has sent chills through the state's $18-billion agricultural industry.
