- SEATTLE - A study of salamanders in Oregon's Cascade mountains provides
evidence that depletion of the Earth's ozone layer is behind an alarming
worldwide decline in amphibians, scientists said Monday.
- More than 90 percent of long-toed salamander
embryos left exposed to the sun's natural ultraviolet rays either failed
to hatch or were born with physical deformities, scientists said in a report
of an experiment conducted last spring.
- By contrast 95 percent of embryos protected
from the so-called UV-B radiation survived, and only 0.5 percent of those
that hatched were deformed. Results of the study were published in the
journal Proceedings of the National Academy of Sciences.
- In the experiment, 200 salamander embryos
in a pond near Sisters, Ore., were protected from the sun's UV-B rays by
acetate filters, while 200 control embryos were placed under filters that
let through 90 percent of the ambient ultraviolet radiation.
- Of the 200 embryos left unprotected only
29 hatched, and 25 of those had deformities including curved tails, blistering
and swollen, fluid-filled areas.
- Andrew Blaustein, a professor of zoology
at Oregon State University in Corvallis and lead author of the study, said
the results were startling to scientists because the salamander embryos
in the study were exposed only to natural sunlight.
- "We didn't enhance any UV levels
or make any changes except to shield some embryos," he said. "We
suggest that ozone depletion and increased UV is probably playing a role
in the decline in amphibian species."
- A widespread decline in the numbers of
some amphibians and even the extinction of some species has been reported
since the late 1980s, especially in Australia, the Western United States
and Central and South America.
- The declines are particularly alarming
to scientists because amphibians are seen as sensitive indicators of environmental
stress and change.
- Blaustein said increased levels of ultraviolet
radiation caused by ozone depletion also is believed to be responsible
for damage to coral reefs, a decline in some species of fish and a loss
of plankton in waters surrounding Antarctica, where ozone depletion is