Human implications are foreseen in study

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http://www.boston.com/news/world/europe/articles/2004/10/15/one_third

_of_amphibian_species_called_threatened/

One-third of amphibian species called threatened

Human implications are foreseen in study

By Carolyn Y. , Globe Correspondent | October 15, 2004

The first vertebrate species to begin hopping and crawling on land

350 million years ago may be the first to die out, according to a

study released yesterday that found a third of all amphibian species

worldwide are threatened with extinction.

Isolated reports of silent forests and empty streams began to

circulate about three decades ago, but the latest assessment is the

first to provide a complete snapshot of a global decline in the

diversity of frogs, salamanders, newts, and worm-like caecilians,

and to show that they are at greater risk than both birds and

mammals.

Scientists say the survey is bad news for humans, too. Amphibians'

permeable skin and dual existence on land and in water make

them " canaries in the coal mine, " early indicators that pollution,

climate change, and overall degradation of the environment may

eventually threaten human life, according to zoologists.

" Amphibians have a moist, wet, rather delicate skin. They absorb

things from their environment and can lose water very quickly

through their skin, " said Geoffrey Hammerson, a research zoologist

who contributed to the report. " They're good red flags for us to

watch. "

The survey, published online by the journal Science, studied the

5,743 known amphibian species and found that at least 1,856 of them

face extinction, more than 100 species may already be extinct, and

43 percent are in a population decline -- many for unknown reasons.

" I've lived a decline, " said coauthor Bruce Young, an international

zoologist of the environmental organization NatureServe who lives in

Costa Rica. " I first came here in 1987 and then you could walk up a

stream during the day, there were these beautiful frogs mottled

yellow and black that were on almost every boulder as you walked. At

night you would hear several, many different kinds of frogs calling.

You'd walk in the forest during the day and frogs would just sort of

hop out under your feet. "

Now, he said, the stream is empty. The nights are quiet.

The study, a three-year collaborative effort between 500 zoologists,

biologists, and wildlife specialists around the world, was organized

by three wildlife organizations: NatureServe, Conservation

International, and the International Union for the Conservation of

Nature. They compiled a database containing the results of thousands

of studies that monitored the populations of individual species in

particular regions.

They determined that 32.5 percent of amphibian species were

threatened with extinction, compared with 12 percent of birds and 23

percent of mammals.

" They've established very convincingly that global declines are true

and are far worse than anyone imagined, " said Hanken, director

of Harvard's Museum of Comparative Zoology.

The authors attributed some of the declines, which have occurred

mainly in tropical areas, to habitat loss or to humans collecting

animals for food, medicine, or pets.

But nearly half of the rapidly declining species are suffering

because of unexplained causes, and could begin to die by the

hundreds over the next decades if nothing is done, the report said.

The mysterious declines are even happening in pristine, well-

protected areas.

Scientists suspect a variety of factors, including the spread of a

deadly fungus that may have originated in Africa, global climate

change, or a combination.

Ultraviolet light also has been shown to weaken the immune responses

of amphibian embryos in studies; a thinning ozone layer could let in

more potentially damaging light, sickening animals.

The spread of the deadly chytrid fungus is poorly understood. The

fungus apparently began spreading in the 1970s, because museum

specimens captured earlier than then are free of it, said Young. He

speculated that the fungus could have been spread by trade in pets

and wild animals, or South African clawed frogs could have spread

the fungus when they were used widely in the 1960s for human

pregnancy tests.

" It starts us thinking that we should be paying attention to these

because parallel things could happen in humans, " Hammerson said.

Even in New England, where native amphibian species aren't

endangered, local declines are common. The Massachusetts endangered

species list includes five of the 10 kinds of salamander that live

in the state -- mostly because of fragmented habitat.

New England's frogs and salamanders depend on vernal pools, shallow

ponds that dry up each summer, to lay their eggs free from the

threat of hungry fish. Such wetland areas are often filled in during

development or cut off by highways and housing complexes from the

forests where adult amphibians live.

Carolyn can be reached at cjohnson@....