Exotic pests bully their way across U.S.

MIAMI — 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.

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 8 feet long and can slip into homes through the plumbing.

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 with devastating ecological and economic consequences.


Moreover, the adaptability of several aggressive plants threatens to create a biological sameness to diverse areas of the country.

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.

Every region of the United States is affected, as are several national parks. Among those especially imperiled are Yosemite, which is troubled by several plants, including a nonindigenous thistle, and he Great Smoky Mountains, which have serious problems with wild hogs. 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 entering 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.And the dangerous African honey bee, imported to the Americas, 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.