The sixth mass extinction of wildlife on Earth is accelerating, according to an analysis by scientists who warn it may be a turning point for the collapse of civilization.
More than 500 species of land animals were found to be on the brink of extinction and likely to be lost within 20 years. By comparison, the same number was lost throughout the last century. Without human destruction of nature, even this rate of loss would have taken thousands of years, the scientists said.
Terrestrial vertebrates on the brink of extinction, with fewer than 1,000 individuals remaining, include the Sumatran rhinoceros, the Clarion wren, the Spanish giant tortoise, and the harlequin frog. Historical data was available for 77 of the species, and the scientists found that they had lost 94% of their populations.
The researchers also warned of a domino effect, with the loss of one species affecting others that depend on it to the limit. "Extinction breeds extinctions," they said, noting that, unlike other environmental problems, extinction is irreversible.
Humanity depends on biodiversity for its health and well-being, the scientists said, and the coronavirus pandemic is an extreme example of the dangers of devastating the natural world. Rising human populations, habitat destruction, wildlife trade, pollution and the climate crisis must be urgently addressed, they said.
"When humanity exterminates other creatures, it is severing the limb on which it sits, destroying functional parts of our own life support system," said Professor Paul Ehrlich, from Stanford University in the United States, and one of the members of the research team. "The conservation of endangered species should rise to a global emergency for governments and institutions, equal to the climate disruption to which it is linked."
"This is our last chance to ensure that the many services that nature provides us are not irretrievably sabotaged," said Professor Gerardo Ceballos, from the National Autonomous University of Mexico, who led the research.
The analysis, published in the journal Proceedings of the National Academy of Sciences, examined data on 29,400 species of terrestrial vertebrates compiled by the IUCN Red List of Threatened Species and BirdLife International. The researchers identified 515 species with populations below 1,000, and about half of them had fewer than 250 remaining. Most of these mammals, birds, reptiles, and amphibians were found in tropical and subtropical regions.
The scientists found that 388 species of terrestrial vertebrates had populations of less than 5,000, and the vast majority (84%) lived in the same regions as species with populations of less than 1,000, creating the conditions for a domino effect.
Known examples of this include the overhunting of sea otters, the main predator of sea urchins that eat seaweed. A boom in urchins devastated kelp forests in the Bering Sea, leading to the extinction of the seaweed-eating Steller's sea cow.
The researchers said their findings could help conservation efforts by highlighting the species and regions that require the most urgent attention.
Professor Andy Purvis of the Natural History Museum in London, who is not part of the new analysis, said: “This research provides another line of evidence that the biodiversity crisis is accelerating. The most difficult problem the researchers faced is that we do not know more about the history of the geographic distributions of the species. They only had that information for 77 of the species at the edge, and we cannot know for sure how typical those species are. "
"But that does not undermine the conclusion," he said. “The biodiversity crisis is real and urgent. But, and this is the crucial point, it is not too late. To make the transition to a sustainable world, we need to tread more gently on the planet. Until then, we are essentially robbing future generations of their inheritance. "
Professor Georgina Mace, University College London, said: "This new analysis highlights some surprising facts about the degree to which vertebrate populations have been reduced worldwide by human activities." But she said she wasn't convinced that simply having a population of less than 1,000 was the best measure of a species that was on the brink. A declining trend for the population is also important and both factors are used on the IUCN Red List, he said.
"Action is important for many reasons, including that we directly and indirectly depend on the rest of life on Earth for our own health and well-being," he said. “Disruption of nature leads to costly and often difficult to reverse effects. Covid-19 is a current extreme example, but there are many more ”.
Mark Wright, WWF science director, said: “The numbers in this research are staggering. However, there is still hope. If we stop land grabbing and devastating deforestation in countries like Brazil, we can begin to bend the curve in biodiversity loss and climate change. But we need global ambition to do that. "