There have been five mass extinction events in Earth’s history, and some researchers say we’re in the midst of a sixth.
Why it matters
Once we lose a species, it’s gone forever. Species losses could have dire consequences for humans, scientists say.
People can help prevent extinctions in ways like volunteering with a conservation organization or reducing their appetite for consumption.
Sixty-six million years ago, a meteor smashed into the coast of Mexico’s Yucatan Peninsula, marking the beginning of the end for most dinosaurs.
“The climate just went nuts,” said Robert Cowie, a professor at the University of Hawaii at Manoa. Within the time span of anywhere from a few decades to a few thousand years, these prehistoric reptiles vanished.
The dinos met their demise during a mass extinction event, one of five to hit Earth. Each of these events wiped out the majority of species living at that time. Now some researchers believe we’re in the midst of a sixth such extinction, and it’s getting worse.
“Fifty years ago, the species who were endangered were very specific, the large animals or the ones who competed with humans and so on,” said Gerardo Ceballos, a professor at the National Autonomous University of Mexico. “But now everything is maybe at risk — the small and big, conspicuous and inconspicuous, the bad and not so bad.”
Past mass extinctions had natural causes, but researchers pin the sixth solely on humans. Still, that also means we have the power to do something about it. Here’s a guide to the sixth mass extinction, which some researchers say will have dire consequences for all life — including us.
What is a mass extinction event?
A mass extinction event involves the disappearance of most species on Earth because of a natural catastrophe, according to Ceballos, who works at UNAM’s Institute of Ecology. They can take place over a few million years, which is fast in geologic terms.
More than 500 million years ago, almost all modern animal groups first appeared during what’s known as the Cambrian Explosion. In the time since, five catastrophic extinction events have occurred that wiped out around 70% or more of all plants and animals. These events included natural disasters such as changes in the gases of the atmosphere or, in the case of the mass extinction that erased most dinosaurs 66 million years ago, an asteroid impact.
From oldest to most recent, the five mass extinction events are: the Ordovician-Silurian, the Late Devonian, the Permian-Triassic, Triassic-Jurassic and the Cretaceous-Paleogene. The Permian-Triassic extinction wais the most deadly, resulting in the loss of about 90% of species. The Cretaceous-Paleogene extinction decimated the dinosaurs.