Exotic Plants, Animals Imperil U.S. Ecosystem : Environment: Florida battles a tenacious tree; Hawaii fights a snake. Billions of dollars are at stake.

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.

But no states are more under siege by pest species than Florida and Hawaii, both geographically isolated subtropical regions as hospitable to foreign plants and animals as they are to tourists. In Hawaii, at least 50% of all plants are exotics; in Florida, the figure is 25% to 30%.

In addition to the problems caused by the melaleuca tree, which infests about 450,000 acres of Everglades wetlands, Florida is also beset by a proliferation of exotic plants, fish, birds and reptiles that have interfered with natural wildlife, fishing and water sports as well as agriculture. Among the more troublesome invaders: the African giant snail, the cane toad, monk parakeet, water hyacinth, Australian pine and fire ants.

“It’s a relatively small number of exotics that are bad,” said Don C. Schmitz of the Florida Department of Environmental Protection. “But it only takes a few to be bullies on the block. And some exotics are like herpes: Once you’ve got it, you’ve got it forever.”

The melaleuca tree seems to be like that. Seemingly immune to disease and competition, the tree pushes out native species and is now rated the single greatest threat to Southern Florida’s ecosystem. After spending millions of dollars annually in largely futile efforts to halt the tree’s spread, scientists are experimenting with an insect that would eat it, according to Schmitz.

Hawaii, a series of islands and the most remote land mass in the world, is even more vulnerable to harm from exotics. Much of the state’s unique plant and animal life already has become extinct and about a third of all species listed or under consideration for listing as endangered are from Hawaii.

Feral European goats and pigs threaten native plants, non-indigenous fresh-water fish far outnumber native species and half of the islands’ original birds are history.

Although Hawaii is the only state subject to a federal agricultural quarantine, introductions of new plants and animals do occur. About 90 of 900 established foreign plants in the islands are considered serious pests.

But nothing carries more potential to harm Hawaii’s fragile ecosystem or its $10-billion annual tourism industry than the brown tree snake. Native to Papua New Guinea and northern Australia, the snake in recent years has become established on Guam, where, according to the OTA report, “the social cost has been great and the ecological impact disastrous.”

As in Hawaii, birds on Guam evolved in a snake-free habitat and thus lack the natural instincts that would protect them from the predator. Of 11 species of forest birds present in 1945, nine have become extinct, the report says. The culprit: the brown tree snake.

The snake is also blamed for electrical outages after becoming entangled in power lines. It even enters homes through sewer lines, air conditioning vents and other openings. Fritts said 91 people were bitten by the mildly venomous snake in the last two years, and 85% of them were attacked in their homes while they slept.

“You just have to look at Guam to see what the economic impact would be in Hawaii,” said Carolyn Imamura of the Pacific Basin Development Council in Honolulu. “I may be more paranoid than normal, but when I’m in Guam I take newspaper and masking tape and plug up all outside access. And I don’t walk under trees.”

In Hawaii, where possession of any snake is illegal, the brown tree snake has turned up six times since 1981, each time at airports after it had arrived from Guam as a stowaway. The federal government is spending about $1.6 million a year on study and control of the snake.

“Miami thinks it has image problems with crime?” said Schmitz of Florida’s Department of Environmental Protection. “Just imagine what happens when the first person in Hawaii or Florida gets a snake bite on the rear while sitting on the pot. You can kiss the tourists goodby.”

As international trade and travel increase, so do the pathways for plants and animals to colonize new habitats, a process the OTA report describes as being “like a game of biological Russian roulette.”

Most scientists see the continuing spread of exotics as inevitable. Of 205 foreign species that have become established in the United States since 1980, 59 are known to be harmful, according to the OTA.

But scientists also see the need for a more comprehensive policy that would at least slow the foreign invasion. Among options the OTA report cites are tightening state regulations on the sale or movement of exotic animals and plants, better education programs and even managed corridors, such as fire breaks, through natural areas susceptible to invasions of pests.

“Ultimately,” said Schmitz, “Congress won’t take this seriously until the environmental community screams. The problem now is that wildlife doesn’t vote, and in the meantime we’re just pouring in the biological pollution. And, literally, the problem is growing.”