The Trees Are Taking Over

By Anastasia Toufexis

From Yankees fleeing the northern cold to Asian walking catfish to South ; American water hyacinths, southern Florida has suffered through many invasions by persistent foreigners threatening to displace native flora and fauna. The vulnerable peninsula, devasted last month by wide-ranging brush fires, continues to be under attack, this time by alien trees: the Brazilian pepper and the Australian pine and Melaleuca, all amazingly prolific and fast spreading. Laments Julia Morton, a University of Miami botanist: "These trees are entirely too healthy. They don't have natural enemies here."

As is so often true, the incursion of aliens was abetted and, in some cases, initiated by well-intentioned but misguided horticulturists. When the Australian pine (Casuarina equisetifolia) gained a foothold in Florida around 1920, landscapers adopted it as a windbreak and hedge. Casuarina rapidly established itself at the edges of canal banks and natural waterways; along the southwest coast of the 1.5 million-acre Everglades National Park, the pine's shallow roots are now so dense that they are destroying the sandy beaches on which the threatened loggerhead sea turtle lays its eggs.

An even greater menace is the Brazilian pepper, or Schinus terebinthifolius. While visiting Brazil in 1926, Physician and Plant Lover George Stone was attracted by its thick clusters of red berries and brought back seeds for his garden in Punta Gorda, on Florida's southwest Gulf coast. The tree proliferated with the aid of casual gardeners, landscapers and birds (which feasted on the berries and spread seeds across the peninsula).

Unsuspecting Schinus boosters have since learned that the Brazilian pepper is a hardy trespasser, resistant to burning and with a proclivity for overrunning cleared land. It now covers thousands of acres along the Everglades' Atlantic and Gulf coastlines and has begun to establish itself among coast-loving mangroves. This worries Robert Doren, a research-management specialist at the park. "Many game fish and shellfish come in to feed or breed among the roots of the mangroves," he explains. "Without the mangroves, you might see the end of most of the estuarine fishery in south Florida."

The real terror of the Everglades is Australia's Melaleuca quinquenervia, also known as cajeput, punk tree and paperbark tree. A close cousin of the eucalyptus, with shaggy bark and pale yellow flowers, it was introduced to Florida in 1906 by Forester John Gifford of the Department of Agriculture, who thought it might attract commercial woodcutters. Unfortunately, its / hardwood interior, hidden by a thick soft bark, is runny with water and difficult to saw. Moreover, the Melaleuca sucks up three times as much water as other swamp trees, thus drying out the land, and its leaves are filled with eucalyptol, an oily flammable substance that turns Melaleuca into an explosive torch when fires roar through the marshlands in dry seasons. Smoke and sparks from burning melaleucas caused numerous accidents on U.S. Highway 27 north of Miami during last month's fires. However, fire does not kill this pest tree; the insulating bark protects it even as the leaves burn. And like the Casuarina and Schinus, the Melaleuca is quick to invade areas scorched clear of native vegetation. Mature Melaleuca stands so solidly that it keeps out wildlife. Says Morton: "When I say solid, a rabbit can't get through." Melaleuca has already colonized 60 sq. mi. of swampland in southern Florida.

Efforts to stem the arboreal tide have been futile. Stymied by a small budget, the National Park Service so far has been limited to spraying herbicides on some stands of Australian pines and attacking Melaleuca by slashing it with machetes and filling the cuts with toxic chemicals. "It's dire," says Marjory Stoneman Douglas, president of Friends of the Everglades, a conservation group. "If nothing is done, these trees are going to take over completely."

With reporting by Andy Taylor/Miami