ALIEN INVASION

The spread of non-native species around the globe, due primarily to modern modes of travel and commerce, is having a devastating impact on vulnerable native species in many areas, unsettling the balance that existed prior to the introduction of the non-native organisms.

Organisms that colonize an area to which they are not native are alternately called "aliens" and "exotics." These terms are used interchangably.

The spread of alien species has become a major cause of concern for wildlife biologists, conservation agencies, and medical professionals around the world. From the outbreak of new diseases, such as the recent introduction of West Nile Fever to the eastern United States, to the devastating commercial losses caused by invasive exotics, such as the zebra mussel in the US midwest, the damage caused by uncontained alien organisms is substantial and far-reaching.

To stem and even undo some of the destruction caused by alien species, we can all lend a hand by doing the following:

• landscaping with native plants.
• shunning exotic pets, which may escape and reproduce.
• spaying or neutering all domestic animals.
• eating locally grown foods.
• protecting old, biologically rich habitats close to home.
• using heirloom varietals in the home garden.

IN THE NEWS:

• Escape of Farmed Salmon Threatens Wild Cousin. The escape of thousands of fish from a Scottish salmon farm will compound the threat to dwindling wild salmon stocks posed by their caged cousins.
• New species of invasive spartina found in Grays Harbor. A new species of the invasive aquatic weed Spartina has been found at Grays Harbor, Washington state's only coastal, deep-water port.
• Ocean study group warns that newly introduced species threaten East and West coasts. An invasion of giant Australian jellyfish clogs shrimp nets in the northern Gulf of Mexico. Swarms of Chinese mitten crabs with a taste for salmon choke water pumps in San Francisco Bay. Along coastal areas home to nearly two-thirds of the U.S. population, the rate of known "bioinvasions" of aquatic species, pathogens, parasites and weeds has increased exponentially over the past 200 years.
• Exotic fish species invading the Great Lakes. Biologists are struggling to control a variety of exotic species that have invaded the Great Lakes.
• Zebra mussels continue to be a problem. It took less than 10 years. Nonnative zebra mussels from Europe first appeared in the Mississippi River in 1991, and today the exploding zebra mussel population has carpeted some parts of the Mississippi River bed with 10,000 to 20,000 mussels per square yard.
  

Suggested reading:

Life Out of Bounds: Bioinvasion in a Borderless World
by Chris Bright. 1998: W.W. Norton & Company. Part of the Worldwatch Institute's environmental issues series.

Tinkering with Eden: A Natural History of Exotics of America
by Kim Todd. 2000. W.W. Norton & Company. This book gives an excellent account of how the many common exotics we encounter everyday in the United States got here and the impacts they've had on native flora and fauna. You may have already known that many of the songbirds flitting about your yard are not native... now you can learn exactly how they got here.

Nature Out of Place: Biological Invasions in the Global Age
by Jason Van Driesche. 2000. Island Press. The ever-increasing globalization of agriculture and commerce is remaking the earth into a "planet of weeds," replacing biological diversity with a seemingly inescapable sameness of forms. This book offers a program of action for people to stem and even undo some of that destruction by landscaping with native plants, shunning exotic pets, eating locally grown foods, and protecting old, biologically rich habitats close to home.