ALIEN INVASION: America's Battle with Non-Native Animals and Plants.

#### ALIEN INVASION: America’s Battle with Non-Native Animals and Plants.

By Robert Devine. National Geographic Books. 288 pp. $24

The nation’s least-known environmental problem is becoming one of the more menacing ones. Exotic species are running amok, driving native species to extinction, degrading natural ecosystems, threatening the public health with diseases that even Hollywood hasn’t discovered. In a cross-country tour to survey the damage, Devine, a journalist, found plenty of evidence of this ecological crisis. He met embattled farmers, botanists, zoologists, scientists, and gardeners, as well as a Sonoma County vintner whose harvest was eaten by herds of wild pigs.

Most non-native species—wheat, soybeans, oranges, tomatoes, rice, apples, and irises, for instance—cause no trouble. The danger comes from plants that are "invasive," a term that is difficult to define because so many imponderables can turn nice plants nasty. For nearly 50 years, Floridians put Asian fig plants in their gardens without incident. A few years ago, the figs suddenly began spreading. It turned out that the plant’s natural pollinator, an Asian wasp, had followed its host to the United States.

Invasive non-native species in the United States date back to the 19th century and before. Ben Franklin brought in Chinese tallow for the production of candle wax; it now overruns bottomland forests and wet prairies in the South. In the 1880s the federal government imported carp; the so-called "wonder fish of Europe" turned out to be a worthless predator here. Ornithologists returned with European house sparrows that rapidly fattened on agricultural crops. Belatedly, restaurant owners put sparrows on the menu, a New York newspaper claimed they made excellent pot pie, and the state of Michigan offered a penny per dead bird. Still the sparrows flourished.

The prize for introducing the greatest number of non-native species goes to the U.S. Department of Agriculture. By 1923 it had introduced more than 50,000 exotic plants, among them crabgrass. Today, an agency within the Department of Agriculture is responsible for checking the millions of ships, plants, and packages that may be transporting larvae, bugs the size of a comma, seeds, even microscopic pathogens. Naturally, aliens sometimes slip through. Serrated tussock, a noxious weed, arrived in packages of seeds from Argentina via Wal-Mart. The Asian tiger mosquito, a carrier of several deadly diseases, came in a shipment of used tires.

After decades of ignoring or underestimating the invasion by non-native species, citizens have begun to take action. The Nature Conservancy, the Audubon Society, and even the Garden Club of America (a longtime holdout) now support the crusade, and many gardeners are switching to native plants. Still, powerful forces stand in the way of change. Congress remains largely unaware of the problem. Animal activists protest whenever a creature, however harmful, is killed. For fun or profit, people still smuggle in dangerous species as pets: tarantulas, geckos, hissing cockroaches. Nurseries resist changing their inventory of invasive plants—such as purple loosestrife, now among the nation’s most destructive—because they’re easy to grow and thus easy to sell.

Devine believes that the menace can be contained. But how? "Biocontrol," the deliberate introduction of the predators and parasites a species leaves at home, has not worked well so far, mostly because the agents end up attacking species other than their targets. Pesticides do the same; companies like Monsanto produce wide-spectrum chemicals to maximize profits. And global warming may exacerbate the problem, the author observes: species now confined to southern climes, such as fire ants and "killer" bees, will likely travel north as the temperature rises.

Calm but not blasé, amused by the attendant ironies but never flippant, Devine observes closely and writes with dramatic intensity. He makes such a compelling case for the problem that only his optimism about its solution seems unwarranted.

—A. J. Hewat