Great Lakes Article:

Invasive species may increase with global warming
mongabay.com
Posted October 13, 2005

New research published in Molecular Ecology suggests that climate change could trigger the expansion of invasive species into wider ranges. The study looked at the genetic history of a goby species in the Eastern Atlantic which appears to have expanded its range dramatically when the world warmed about 150,000 years ago.

The finding has broader implications beyond aquatic reef fish. Invasive species cause billions of dollars in damage per year. In the United States alone, the economic cost of invasive species -- in terms of the damage they do and the expense of controlling them -- is estimated at $137 billion a year, according to a study by Cornell University in 1999. Should global warming fuel the arrival of more non-native species, the cost -- both economic and ecological -- will likely rise as well.

Why are invasive species so destructive?

While ninety percent of immigrant species do no obvious harm to their new home environment, a small number do disproportionate damage. By definition, "invasive species" are "an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health" (U.S. Executive Order 13112). Invasive species disrupt ecosystems primarily by preying on local species and competing with native species over limited resources. The effect on native biodiversity can be severe -- the Cornell study says that 42% of the species on the Threatened or Endangered species lists are at risk primarily because of non-indigenous species. Introduced tilapia and Nile Perch have devastated endemic fish populations throughout Africa, while the snakehead, a carnivorous fish capable of walking across land, has raised fears every time it appears in a pond in the Eastern United States. Further, there can be significant economic costs to the damage caused by such aliens. For example, removing the zebra mussel from the Great Lakes alone will cost $5 billion. The mollusk is a problem because it clogs water intakes for factories, interferes with navigation, accelerates, decreases fuel efficiency, damages engines, reduces the amount of food available for other filter-feeding organisms and fish, and competes with native mussels.

A warmer climate could mean more foreign tropical species could find their way to, and thrive in, the United States. Florida and Hawaii, the country's two most tropical states, have arguably suffered the most from invasive species. The python, a species of snake that has invaded the Everglades after pet owners have released it into the wild, has recently made headlines as it battles native alligators at the top of the food chain.

Dramatic battles aside, the ecological and economic threat from invasive species is real and should serve as a reminder to what's in store for a warmer world.