endangered okapi
May 31, 2014

Rapidly Vanishing Species Could Lead To Earth’s ‘Sixth Great Extinction’

redOrbit Staff & Wire Reports - Your Universe Online

Plant and animal species are becoming extinct at rates more than 1,000 times more quickly than they did before the arrival of humans, indicating that the Earth could be edging closer to a sixth great extinction, according to a new study published May 30 in the journal Science.

In the study, Duke University biologist Stuart Pimm and his colleagues examined both past and present rates of extinction using the IUCN Red List of Threatened Species and related resources. While performing their review, the researchers discovered that the historical extinction rate was lower than scientists had originally believed.

As a result of their investigation, Pimm told Associated Press (AP) Science Writer Seth Borenstein that his team now believes that species are dying out globally approximately 10 times more quickly than biologists had believed. Pimm added that the planet is “on the verge of the sixth extinction,” and that whether or not it can be avoided “will depend on our actions.”

The new research, which Borenstein said is being hailed as a landmark study by the scientific community, focuses specifically on the extinction rate and not the actual number of species vanishing from the planet. The authors calculated a “death rate” of species that become extinct annually out of one million unique species.

“Calculating extinction rates can be difficult, in part because no one knows exactly how many species there are,” explained Christine Dell'Amore of National Geographic. Experts have managed to identify at least 1.9 million animal species, and the study reported that there are at least 450,000 types of plants in existence, she added.

Pimm told Dell’Amore that conservationists are able to calculate the extinction rate of those species by tracking how many of them die out each year, similar to the technique used to determine a country’s mortality rate. Based on that approach, the study authors determined that between 100 and 1,000 species were lost per million per year, primarily due to climate change and habitat destruction resulting from human causes.

The investigators used a different method to calculate the extinction rate from before the evolution of the modern human. They reviewed fossil record data and took note of when species disappeared, then used statistical modeling to fill in holes in the records, Dell’Amore said. Those efforts revealed that less than one species out of every million became extinct annually in the time before modern humans evolved, she added.

One of the species at risk is the buffy-tufted-ear marmoset, a creature with thick black fur and a perpetually disgruntled look on its face, explained Washington Post reporter Terrence McCoy. The marmoset once resided in the jungles of Brazil, but tremendous increases in human population led to extensive destruction of its habitat for agricultural purposes, placing the species in grave danger.

The study also helped clarify the locations of the most vulnerable species, as well as where and how people cause changes to the environment and what role that plays in extinctions, McCoy said. Pimm and his associates report that many land-based species are distributed throughout regions smaller than the state of Delaware, and that these creatures are “geographically concentrated and are disproportionately likely to be threatened or already extinct.”

“Five times, a vast majority of the world's life has been snuffed out in what have been called mass extinctions, often associated with giant meteor strikes,” Borenstein said. “About 66 million years ago, one such extinction killed off the dinosaurs and three out of four species on Earth. Around 252 million years ago, the Great Dying snuffed out about 90 percent of the world's species.”

Fortunately, Pimm and his colleagues said there is still hope, thanks largely to the use of smartphones and other types of technology that can help biologists, other scientists and even conservation-minded citizens locate plant and animal species that are in trouble. Once they are detected, scientists can attempt to protect habitats and use techniques such as captive breeding in order to preserve the threatened plants and animals.