- HALIFAX, Nova Scotia, Canada
(ENS) - The first estimate of extinction rates of North America's freshwater
animals, just released, has found they are the most endangered species
group on the continent. The Canadian study warns that the U.S. could lose
most of its freshwater species in the next century if steps are not taken
to protect them.
- "A silent mass extinction is occurring in our lakes
and rivers," says author Anthony Ricciardi of Dalhousie University
in Halifax. Ricciardi,s study with coauthor Joseph Rasmussen of McGill
University in Montreal is published in the October issue of "Conservation
- Northern shore of Lake Superior in Minnesota (Photo by
Dave Hansen courtesy Great Lakes National Program Office) Relatively little
media attention has been given to freshwater species, the authors say,
but these animals are in at least as much danger as land species. Since
1900, at least 123 freshwater animal species have been recorded as extinct
in North America.
- Common freshwater species, from snails to fish to amphibians,
are dying out five times faster than land species, and three times faster
than coastal marine mammals, the researchers found. Their estimate of the
loss of freshwater biodiversity "is probably conservative," the
researchers say, "because there have likely been extinctions of species
that we did not know existed, as suggested by the fact that several extinct
fishes are known from only a few specimens."
- Freshwater animals are dying out as fast as rainforest
species, considered by many to be the most imperiled on Earth. The authors
predict that about four percent of freshwater species will be lost each
decade if nothing is done to conserve them.
- Worldwide the situation is even more perilous for these
creatures. The World Wide Fund for Nature (WWF) said in September that
51 percent of freshwater species, from fish and frogs to river dolphins,
are declining in numbers. The 1999 Living Planet Report, an annual index
on the state of the world's natural wealth, presents the most reliable
data available on forest area and populations of marine and freshwater
species worldwide. It also examines consumption of critical resources in
151 countries and its consequences.
- "This report is a graphic call to reduce these negative
trends as the world enters the 21st century," said Claude Martin,
director general of WWF. "The observed declines in populations of
freshwater species is particularly alarming as they indicate the extent
of deterioration in the quality of the world's rivers, lakes and other
- Toad in Britain (Photo by Ian Britton courtesy <http://www.freefoto.comfreefoto.com)
- Freshwater amphibians are hard hit. The disappearance
of the golden toad and other amphibians in Costa Rica has been attributed
to climatic changes. Many losses have been recorded in national parks and
nature reserves, indicating pervasive threats even in protected areas.
In Australia, Panama and the US, about 20 frog species have been decimated
by a previously unknown fungus. Deformities are also widespread, caused
by pollutants such as pesticides and other factors.
- The report, produced by WWF in collaboration with the
New Economic Foundation and the World Conservation Monitoring Centre (IUCN),
found that the total of marine and inland fish caught reached a record
level of 95 million tonnes in 1996, up 11 million tonnes from the annual
average in the preceding five years.
- To get a picture of how rapidly species extinction is
accelerating, the Canadian researchers compared current extinction rates
with those from the fossil record. They calculate that the background rate
of extinction for freshwater fish species is about one species every three
- The modern extinction rate in North America, the study
says, is about one extinction every 2600 years - about 1,000 times higher
than the background rate.
- Ricciardi and Rasmussen predict that many species considered
at risk will disappear within the next century. At risk species account
for 49 percent of the 262 remaining mussel species, 33 percent of the 336
crayfish species, 26 percent of the 243 amphibian species, and 21 percent
of the 1,021 fish species.
- Sea lampreys on lake trout (Photo courtesy U.S. Fish
& Wildlife Service)
- Non-native species pose a serious threat to indigenous
freshwater animals. European zebra mussels are outcompeting native mussels
in North American lakes and rivers. Sea lampreys invade lakes and attach
themselves to native fish, killing them. Even sport fish transplanted from
one lake to another can take over an ecosystem, driving less aggressive
native fish toward extinction.
- Dams that obstruct river flow are also threats. Of 5.2
million kilometers (3.2 million miles) of stream habitat in the lower 48
states, less than two percent, or about 100,000 kilometers, is pristine
enough to be federally protected, Ricciardi and Rasmussen say. Excess sediment,
toxic contaminants and organic pollutants from agriculture threaten most
- Only 40 rivers longer than 200 kilometers (125 miles)
remain free flowing in the lower 48 states. "Such massive habitat
deterioration threatens some of the world,s richest freshwater faunal assemblages,"
the study says. Ricciardi and Rasmussen note that hundreds of U.S. dams
are coming up for federal relicensing soon, providing an opportunity to
reestablish natural flows in many rivers.
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