Sixty-six million years ago Planet Earth experienced one of the largest mass extinctions in its entire history. Within what counts as a blink of an eye in geological time the dinosaurs, which had ruled the planet for hundreds of millions of years, died out en masse.
We’re experiencing just such a mass extinction of species right now. And this time it isn’t an asteroid that’s to blame. It’s us.
According to a recent study published in the journal Proceedings of the National Academy of Science in the US, Earth is entering a period of colossal losses of biodiversity. The three authors of the study examined the status of 27,600 terrestrial vertebrate species: amphibians, reptiles, birds and mammals. They also conducted a detailed analysis of how 177 specific mammal species, such as cheetahs and Bornean orangutans, had fared between 1900 and 2015.
Their conclusion: “an extremely high degree of population decay in vertebrates, even in common ‘species of low concern.’”
In layman terms this means that wildlife populations worldwide have been experiencing dramatic drops in their numbers and sizes because of human activities. “This ‘biological annihilation’ underlines the seriousness for humanity of Earth’s ongoing sixth mass extinction event,” they write. “In the 177 mammals for which we have detailed data, all have lost 30% or more of their geographic ranges and more than 40% of the species have experienced severe population declines (>80% range shrinkage).”
Over the past century, the experts say, nearly 200 species have gone extinct already, which translates into a rate of two species per year. In all, untold numbers of individual animals that once thrived on Earth have disappeared within a few short decades. “This is the case of a biological annihilation occurring globally, even if the species these populations belong to are still present somewhere on Earth,” said Rodolfo Dirzo, the study’s co-author who is a professor of biology at Stanford University.
This man-made mass extinction, which is variously called the Sixth or Holocene or Anthropocene Extinction, “is already here and the window for effective action is very short, probably two or three decades at most,” the study’s authors say. Time is pressing because “all signs point to ever more powerful assaults on biodiversity in the next two decades, painting a dismal picture of the future of life, including human life.”
“Avoiding a true sixth mass extinction will require rapid, greatly intensified efforts to conserve already threatened species and to alleviate pressures on their populations — notably habitat loss, overexploitation for economic gain, and climate change,” write the authors of another study, this one published in the journal Science Advances. “All of these are related to human population size and growth, which increases consumption (especially among the rich), and economic inequity. However, the window of opportunity is rapidly closing.”
Unless we act and do so fast to reverse harmful trends, most life on Earth will have gone the way of the dinosaurs. “We have the potential of initiating a mass extinction episode which has been unparalleled for 65 million years,” Gerardo Ceballos, a Mexican ecologist, explained. “But I’m optimistic in the sense that humans react — in the past we have made quantum leaps when we worked together to solve our problems.”