The study, published in the journal PLOS ONE, gives the first estimate of how rapidly frogs, toads and salamanders in the U.S. are disappearing. Carried out by scientists from the U.S. Geological Survey (USGS), under the auspices of the USGS Amphibian Research and Monitoring Initiative, the research was undertaken over 9 years and looked at 48 amphibian species.
Worryingly, the results showed that amphibian populations across the country are affected, and even species that were thought to be stable and widespread are showing declines. Even more alarmingly, these declines are also occurring in protected areas such as national parks and wildlife refuges.
On average, the populations of the amphibians studied were disappearing at a rate of 3.7% a year. If this continues, these species would disappear from half of their current habitat in the next 20 years.
“Even though these declines seem small on the surface, they are not,” said Michael Adams, the lead author of the study. “Small numbers build up to dramatic declines with time. We knew there was a big problem with amphibians, but these numbers are both surprising and of significant concern.”
The outlook is even worse for species already listed as threatened on the IUCN Red List, which are vanishing at a rate of 11.6% each year. At this rate, these species could disappear from half the habitats they currently occupy in just six years.
“Amphibians have been a constant presence in our planet’s ponds, streams, lakes and rivers for 350 million years or so, surviving countless changes that caused many other groups of animals to go extinct,” said Suzette Kimball, USGS Director. “This is why the findings of this study are so noteworthy; they demonstrate that the pressures amphibians now face exceed the ability of many of these survivors to cope.”
Causes of amphibian declines
The study did not look at the causes of the amphibian declines, but amphibians worldwide are known to be facing a wide range of threats, including habitat loss, invasive species, pollution and disease, particularly the deadly fungal disease chytridiomycosis.
The surprise finding that amphibians are declining even in areas managed for conservation, such as national parks, suggests that the factors affecting these species are widespread.
“The declines of amphibians in these protected areas are particularly worrisome because they suggest that some stressors – such as diseases, contaminants and drought – transcend landscapes,” said Michael Adams. “The fact that amphibian declines are occurring in our most protected areas adds weight to the hypothesis that this is a global phenomenon with implications for managers of all kinds of landscapes, even protected ones.”
Amphibians are important components of healthy ecosystems, providing food for other animals and helping to control pests. They also provide a source of medicines for humans, and are beautiful and fascinating creatures in their own right.
According to Brian Gratwicke of the Smithsonian Conservation Biology Institute, “[These findings are] very bad news for amphibians. Now, more than ever, we need to confront amphibian declines in the U.S. and take actions to conserve our incredible frog and salamander biodiversity.”
You can also have a go at becoming a conservation superhero and helping save amphibians on ARKive’s online game, Team WILD!
Liz Shaw, ARKive Text Author