Invasive species may increase with
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.