by Shanika Gunaratna: Over the last half-billion years, scientists say there have been five mass extinction events on Earth…
in which a wide diversity of species on this planet suddenly died off. Now, there’s growing evidence that a sixth mass extinction is unfolding, according to scientists who track species around the globe. In a new study, researchers say the currentis even “more severe than perceived” and amounts to “biological annihilation” affecting thousands of species.
In the study, published Monday in the journal Proceedings of the National Academy of Sciences, researchers from Stanford University and the National Autonomous University of Mexico unveiled a granular look at population trends among 27,600 species of birds, amphibians, mammals, and reptiles — half of the world’s known terrestrial vertebrates — including detailed analysis of 177 species of mammals.
The results are grim: researchers found an “extremely high degree of population decay” among vertebrates, even in species considered at low risk of extinction. In general, they found that the world’s temperate regions are losing species at equal or even higher rates than the tropics.
“Earth is experiencing a huge episode of population declines and extirpations” — when a species ceases to exist in a particular location — “which will have negative cascading consequences on ecosystem functioning and services vital to sustaining civilization,” the researchers wrote.
“We describe this as a ‘biological annihilation’ to highlight the current magnitude of Earth’s ongoing sixth major extinction event.”
Pushed to the brink
Dividing the world’s land masses into a grid of 22,000 sections measuring 10,000-square-kilometers (about 3,860 square miles) each, the researchers tracked species declines and painted a stark picture of populations being pushed to their limits.