Washington, August 13 : Researchers from the University of California, Berkley, US, have suggested that the devastating declines of amphibian species around the world are a sign of a large-scale biodiversity disaster.
In an article published online in the journal Proceedings of the National Academy of Sciences, the researchers argue that substantial die-offs of amphibians and other plant and animal species add up to a new mass extinction facing the planet.
"There's no question that we are in a mass extinction spasm right now," said David Wake, professor of integrative biology at UC Berkeley.
"Amphibians have been around for about 250 million years. They made it through when the dinosaurs didn't. The fact that they're cutting out now should be a lesson for us," he added.
New species arise and old species die off all the time, but sometimes the extinction numbers far outweigh the emergence of new species. Extreme cases of this are called mass extinction events, and there have been only five in our planet's history, until now.
The sixth mass extinction event, which Wake and others argue is happening currently, is different from the past events.
"My feeling is that behind all this lies the heavy hand of Homo sapiens," said Wake.
According to Wake, there is no consensus among the scientific community about when the current mass extinction started.
It may have been 10,000 years ago, when humans first came from Asia to the Americas and hunted many of the large mammals to extinction. It may have started after the Industrial Revolution, when the human population exploded.
"Or, we might be seeing the start of it right now," said Wake.
"But no matter what the start date, empirical data clearly show that extinction rates have dramatically increased over the last few decades," he added.
The global amphibian extinction is a particularly bleak example of this drastic decline.
In 2004, researchers found that nearly one-third of amphibian species are threatened, and many of the non-threatened species are on the wane.
The most startling drop in amphibian populations has been happening in the US. Of the seven amphibian species that inhabit the peaks of the Sierra Nevada, five are threatened.
Wake and his colleagues observed that, for two of these species, the Sierra Nevada Yellow-legged Frog and the Southern Yellow-legged Frog, populations over the last few years declined by 95 to 98 percent, even in highly protected areas such as Yosemite National Park.
The culprit is a nasty pathogenic fungus that causes the disease chytridiomycosis. Scientists have documented over the last five years mass die-offs and population collapses due to the fungus in the mountain range.