The disappearance of entire species is not the only factor that contributes to mass extinction, it is also the reduction of populations within species, a new study argues, and calls the current rate of loss of terrestrial vertebrate populations a prelude to the sixth mass extinction. Prof Gerardo Ceballos, at the Universidad Nacional Autónoma de México, who led the work, said: “The situation has become so bad it would not be ethical not to use strong language.”

Previous studies have shown species are becoming extinct at a significantly faster rate than for millions of years before, but even so extinctions remain relatively rare giving the impression of a gradual loss of biodiversity. The researchers mapped the ranges of 27,600 species of birds, amphibians, mammals and reptiles - a sample representing nearly half of known terrestrial vertebrate species - and analyzed population losses in a sample of 177 well-studied mammal species between 1990 and 2015. Read: 60% Of Primates, Closest Human Relatives, Could Be Extinct In 25 Years

“Using range reduction as a proxy for population loss, the study finds 32 percent of vertebrate species are declining in population size and range. Of the 177 mammals for which the researchers had detailed data, all have lost 30 percent or more of their geographic ranges and more than 40 percent have lost more than 80 percent of their ranges,” a statement on the Stanford site said. Ehrlich had been part of another study in 2015 that “showed that Earth has entered an era of mass extinction unparalleled since the dinosaurs died out 66 million years ago.” Further, according to data maintained by the International Union for Conservation of Nature, about 41 percent of all amphibian species and 26 percent of all mammals were threatened by extinction, as of March 2016. And a new study calls the loss of that wildlife a “biological annihilation” and a “frightening assault on the foundations of human civilization.” Researchers from the Universidad Nacional Autónoma de México found that the rate of population loss is extremely high — even among species that are not considered endangered. “Anthropogenic population extinctions amount to a massive erosion of the greatest biological diversity in the history of Earth and that population losses and declines are especially important, because it is populations of organisms that primarily supply the ecosystem services so critical to humanity at local and regional levels,” the study says. It is a prelude to the disappearance of many more species and the decline of natural systems that make civilization possible.”

Giving examples of the importance of animals in any healthy ecosystem and even to humans, such as the pollination of crops by honeybees, Ehrlich said in the statement: “Sadly, our descendants will also have to do without the aesthetic pleasures and sources of imagination provided by our only known living counterparts in the universe.”

The authors cite human overpopulation and overconsumption in their study as the primary reasons driving the loss of individual members of various species, as well as the loss of species (two vertebrate species go extinct every year, on average), and call to undo “the fiction that perpetual growth can occur on a finite planet.” “We emphasize that the sixth mass extinction is already here and the window for effective action is very short, probably two or three decades at most. Read next Massive underground magma pulse caused the world's largest mass-extinction Massive underground magma pulse caused the world's largest mass-extinction

His work, published in the journal Proceedings of the National Academy of Science, tracks the significant rate of mammalian extinction across the Earth - describing it as a “frightening assault on the foundations of human civilisation”.
Between 1900 and 2015, around 177 species of mammals have lost 80% of their distribution leading to a presumption that the Holocene extinction is accelerating.