Eradication

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Eradicating invasive species from a habitat requires hard work with sprays, poisons, and backbreaking labor plus another obstacle: people’s opposition to eradication programs. Few people mourn the loss of a million or so zebra mussels from a lake, but they feel differently about hunts to reduce invading deer, pigs, golden eagles, hawks, rabbits, or foxes.

Eradication programs use chemical, physical, or biological methods. Chemicals have been tried on the Great Lakes zebra mussels, but it is difficult to attain a high enough concentration of any chemical that will not also injure native species. An eradication program in northern California’s Lake Davis has been used to remove northern pike released by fishermen more than a decade ago. The pike devour other fish in the Davis watershed along with frogs, crayfish, and ducklings. Biologists have tried the chemical rotenone in a long-term program to rid the lake of the pike, but the
poison also kills all the native fish. After eliminating the pike, biologists then must restock the lake with native fish. Residents near Lake Davis have been leery of this type of chemical eradication, especially since the pike have evaded more than one attempt to wipe them out. In 2007 USA Today quoted Bill Powers, mayor of a nearby community, as cautioning, “I agree with the scientists who say there’s no safe levels of carcinogens in drinking water,” when he discussed possible contamination of the aquifers near the lake. Store owner Tammy Milby gave her opinion on the economic harm caused by the pike’s invasion of one of California’s favorite fishing lakes: “Hopefully it’ll work this time. I don’t know if the community, the businesses, can handle another failure.” Powers and Milby both express the
concerns attached to eradication programs.

Physical eradication consists of hunting and trapping. Trapping programs capture invasive animals so biologists can humanely release them into a less sensitive habitat. Sometimes, however, exotic animals require speedy capture because they have entered an environment that does not suit them, and leaving them in the habitat would be inhumane. People release reptiles, amphibians, tropical fish, and tropical birds intentionally or accidentally into places that endanger the animal. Owners of exotic animals do not always understand the special needs of these pets, and the animals die soon after being released because they are not adapted to the climate, food, or other conditions in an unfamiliar environment. Though some exotic animals can go extinct for these reasons, others cause an opposite problem: They aggressively invade the new habitat. Swamps, woodlands, and grasslands have all been victimized this way by exotic species. Like other invasive species, exotic species prey upon native animals, threaten keystone and flagship species, and consume plants or prey needed by others in the natural ecosystem.

Hunting programs consist of tracking and killing invasive animals. Hunters licensed by the Fish and Wildlife Service (FWS) or private contractors hired by government agencies perform the eradication. Many people oppose hunting on ethical grounds, especially if leg-hold traps or dogs are used to catch the animals. Eradication is also criticized when
people have become accustomed to an invasive species and now consider them regular inhabitants. In 2005 a heated debate ensued over the hunting of feral pigs on the Channel Islands off California’s coast, brought there by farmers in the 1850s. Animal-protection advocate Scarlet Newton told a local university newspaper, the Daily Nexus, “The island pig has no malice. It is just gently looking for food and is not causing a fraction of the damage humans have caused. The best solution is to leave the ecosystem alone. It is as stable as it can be and still be vital.” Eradication by hunting will likely remain a very controversial way to stabilize animal populations.

Wildlife experts have also begun to use biological eradication in which they put a species into an imbalanced ecosystem with the intent to combat an invader. Vineyards, for example, contain only one type of vegetation (call a monoculture) that upsets the natural ecosystems of the original woods, meadows, or hillsides. Vineyards often draw gophers, ground squirrels, feral pigs, and birds that feed on vines, uproot plants, or build dens. Many vintners encourage natural predators to enter the area as an alternative to chemical poisoning, hunting, or trapping. Sustainable vineyards have relied on foxes, coyotes, and raptors living in the area to deter invaders.