One-third Of Amphibians
By Steve Connor
15 October 2004
They were the first animals with backbones
to walk on land. They witnessed the rise and fall of the dinosaurs and
were present at the birth of a bipedal ape who went on to become the
most destructive species the planet has ever known.
Amphibians - frogs,
toads, newts and salamanders - are among the longest surviving animals
on earth, yet something dramatic now threatens that longevity. And mankind
A global study revealed
yesterday that almost a third of amphibians face extinction - and pollution
is cited as the biggest cause. The three-year survey, involving 500
scientists from more than 60 countries, has found that a third of the
5,743 known species are threatened with being wiped out and at least
427 are so critically endangered that they could disappear tomorrow.
The animals are
so sensitive to the man-made environment that scientists have likened
them to the canary in a coal mine - songbirds that fell silent, killed
in the presence of odourless gas. The latest and most comprehensive
study of amphibians around the world has shown that for many species
of frogs and their nearest relatives the singing has suddenly and inexplicably
stopped - and the same bipedal ape is almost certainly responsible.
"This is a
problem way outside what we know," said Simon Stuart of the World
Conservation Union and leader of the study published in the online version
of the journal Science.
Dr Stuart said:
"This level of decline is ... extraordinary and serious because
amphibians represent a very important part of the overall diversity
of life. Since most amphibians feel the effects of pollution before
many other forms of life, their rapid decline tells us that one of earth's
most critical life support systems is breaking down."
The figures in the
survey are almost certainly underestimates because more than 22 per
cent of the known amphibian species are too poorly understood for the
researchers to reach a reliable conclusion about what is happening to
Populations of almost
half of the known amphibian species are in decline. While 32 per cent
of amphibians are threatened with extinction, only 12 per cent of birds
and 23 per cent of mammals are in the same position. The latest study
estimates that up to 122 species have gone extinct since 1980.
Dr Stuart said that
all animal groups undergo a natural "background" rate of extinction
but, in the case of amphibians, the actual loss of species is equivalent
to the total number of background extinctions for many tens of thousands
of years being squeezed into a single century.
line is that there's almost no evidence of recovery and no known techniques
for saving mysteriously declining species in the wild. It leaves conservation
biologists in a quandary," Dr Stuart said.
Amphibians are considered
uniquely sensitive to man-made changes in the environment. Their moist,
porous skins are vulnerable to water-borne toxins and infections, and
their reliance on two habitats - freshwater and land - means they cannot
survive properly without both.
suggested many possible reasons for the decline. Pollution of both water
and the atmosphere, human exploitation for food and medicine and habitat
destruction all pose serious threats.
But it is clear
that amphibians are also disappearing from what appear to be pristine
habitats. At one protected site in Costa Rica, for instance, some 40
per cent of amphibians disappeared over a short period in the late 1980s.
Other losses occurred almost simultaneously in Costa Rica, Ecuador and
It is this so-called
"enigmatic decline" that poses the biggest problem for conservationists
simply because they have little idea about what needs to be done to
address the problem.
The authors of the
report say: "Enigmatic decline species present the greatest challenge
for conservation because there are no known techniques for ensuring
their survival in the wild. Most enigmatic declines have been recorded
from the Americas south to Ecuador and Brazil, Australia and New Zealand,
but they are spreading, for instance to Peru, Chile, Dominica, Spain
Many of these mysterious
disappearances seem to take place in tropical habitats involving amphibians
living in mountain streams. Some studies suggest they may be linked
with the global spread of a fungus called chytridiomycosis, which may
be exacerbated by global warming. What is most worrying is that the
decline in amphibians is occurring across the world.
Bruce Young, a zoologist
who took part in the global amphibian assessment, said: "We already
knew amphibians were in trouble, but this assessment removes any doubt
about the scale of the problem." Dr Achim Steiner, director general
of the World Conservation Union, said: "The fact that one third
of amphibians are in a precipitous decline tells us that we are rapidly
moving towards a potentially epidemic number of extinctions."
president of Conservation International, said: "Amphibians are
one of nature's best indicators of overall environmental health. Their
catastrophic decline serves as a warning that we are in a period of
significant environmental degradation."