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Jeff Houlahan
This study backs up what everyone has been saying
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Wednesday, 12 April, 2000, 17:51 GMT 18:51 UK
Amphibians facing global decline
Frog BBC
Some amphibians are changing colour because of stress
By environment correspondent Alex Kirby

Evidence shows amphibians have been in decline globally for the last half-century, say researchers.

Over the last 40 years, they say, the decline has averaged 4-5% annually, with some especially steep falls seen during the 1960s.

The decline is yet another indicator of the long-term decline in biodiversity on this planet

Jeff Houlahan
After a rapid shrinking then, the rate of population decline eased off, although it is still continuing.

The researchers say their findings support the widespread impression of amphibian decline, which has until now been largely based on anecdotal evidence.

The research team, whose work is reported in the science magazine Nature, was led by Jeff Houlahan, of the University of Ottawa in Canada. It also included scientists from Switzerland and Russia.

They used data from 936 separate amphibian populations, and unpublished data from herpetologists around the world.

'Conclusive proof'

The team says this was to avoid relying on evidence that was "either anecdotal or derived from short-term studies at small geographical scales".

It notes the persistent reports of catastrophic amphibian population crashes in Australia, south and central America, and high-altitude parts of the western US.

Frog BBC
Declines are still continuing
These reports have suggested local climate changes, acid rain, disease, increased solar radiation, or a combination of several of these, as possible causes.

But most documented the disappearance of amphibians from small regions, making extrapolations to the global scale difficult.

The researchers say they think their work provides conclusive proof of the decline of amphibians, which include frogs, toads, newts and salamanders.

More than 200 scientists contributed data from 37 countries, covering 157 species from 21 families. The studies range from two to 31 years in duration.

The team found:

  • no significant trend from 1950 to 1960
  • a steep decline from 1960 to 1966 (an annual rate of about 15%)
  • a shallower decline from 1966 to 1997 (about 2% annually).
They say: "This apparent difference in rates of decline for the two time periods should be treated cautiously because of the relatively small sample sizes for the early years."

They also found that while amphibians declined during the 1960s in both North America and Western Europe, it was only the American populations that seemed to fall from 1966 to 1997.

Late alarm call

Using a second assessment method, based on the ratio of declining to increasing populations, the team found significantly more declines than increases in every region.

Jeff Houlahan said: "The most serious population decline may have occurred long before scientists noticed and sounded the alarm.

"And though the sample size in the 1960s is small, the decline is yet another indicator of the long-term decline in biodiversity on this planet."

Frog BBC
Deformities worry scientists
The researchers say their analysis suggests that at a global scale "amphibians have declined over the past several decades and continue to do so."

Only 61 of the 936 populations studied became extinct, and only one of those during the period of most significant decline, from 1960 to 1966.

The team reports that this provides evidence that even existing populations have undergone strong declines.

It says its analysis also suggests recent declines, especially in North America and in Australia and New Zealand.

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