The scientists who were among the first to declare the world’s sixth mass extinction event was already underway in a 2015 study, have published new research revealing the rate at which wildlife is being destroyed is accelerating and is a direct threat to human civilisation.

Stanford biologist Paul Ehrlich and colleagues at other institutions report in the new paper that the extinction rate is likely much higher than previously thought and is eroding nature’s ability to provide vital services to people.

They state the wildlife trade combined with other human impacts have now wiped out hundreds of species forever, and pushed even greater numbers to the brink of extinction “at an unprecedented rate”.

To help understand the rapid ramping-up of the scale of the disaster, the authors said it is estimated that over the course of the entire twentieth century, at least 543 land vertebrate species went extinct.

In the new study, Professor Ehrlich and his coauthors estimate around the same number of species are likely to go extinct in the next two decades alone.

The huge increase in extinctions and rate of wildlife destruction will have a disastrous impact on humans too, the authors warn, with an intensification of health threats such as we have seen with the current Covid-19 pandemic.

The virus is currently believed to originally be of animal origin, and passed to humans due to spillover infection – where a population with a high pathogen prevalence comes into contact with another potential host population. As human activity forces wild animals into more restricted areas, the reservoirs of infection are more likely to grow and more likely to then spillover into humans and other species.

“When humanity exterminates populations and species of other creatures, it is sawing off the limb on which it is sitting, destroying working parts of our own life-support system,” said Professor Ehrlich.

“The conservation of endangered species should be elevated to a national and global emergency for governments and institutions, equal to climate disruption to which it is linked.“

The study comes after a cross-party group of US politicians has urged the Trump administration to close unregulated wildlife markets as well as those selling live animals for food, in an effort to stop the trade in illegal wildlife and wildlife products.

The study says that human pressures, such as population growth, habitat destruction, the wildlife trade, pollution and climate change, are the key factors which are critically threatening thousands of species around the world.

Ecosystems ranging from coral reefs and mangrove forests to jungles and deserts depend on the specially-adapted species which live in or on them and their long-evolved symbiotic relationships to maintain their functioning and make them resilient to change.

Without this robustness, ecosystems become less and less able to preserve a stable climate, provide freshwater, pollinate crops and protect humanity from natural disasters and disease, the scientists said.

Working to gain a better understanding of the extinction crisis, the researchers looked at the abundance and distribution of critically endangered species.

They found that 515 species of terrestrial vertebrates – 1.7 percent of all the species they analysed – are now on the brink of extinction, meaning they have fewer than 1,000 individuals remaining.

About half of the species studied have fewer than 250 individuals left on the planet.

Most of the highly endangered species are concentrated in tropical and subtropical regions that are affected by human encroachment, according to the study.

In addition to the alarming extinction rates, the cumulative loss of populations – the individual, localised groups of a particular species – and the geographic range they inhabit, has led to more than 237,000 populations of those 515 species being wiped out since 1900, according the researchers’ estimates.

With fewer existing populations, species are unable to serve their function in an ecosystem.

This can have a ripple effect, the authors said. For example, they cited the overhunting of sea otters in the 1700s: the otters had been the main predator of kelp-eating sea urchins. When the sea urchin population boomed without any predators, there were mass kelp die-offs, directly resulting in the kelp-eating sea cow going extinct.

“What we do to deal with the current extinction crisis in the next two decades will define the fate of millions of species,“ said study lead author Gerardo Ceballos, a senior researcher at the National Autonomous University of Mexico’s Institute of Ecology.

“We are facing our final opportunity to ensure that the many services nature provides us do not get irretrievably sabotaged.”

The extinction of endangered creatures could have a domino effect on other species, according to the researchers. The vast majority – 84 percent – of species with populations under 5,000 live in the same areas as species with populations under 1,000. This proximity creates the conditions for a chain reaction in which the extinction of one species destabilises the ecosystem, putting other species at higher risk of extinction.

“Extinction breeds extinction,” the study says. The researchers are calling for all species with populations under 5,000 to be listed as critically endangered on the International Union for Conservation of Nature Red List, an international database used to inform conservation action on a global scale.

The team said the findings of the study could aid conservation efforts by highlighting which species and geographic regions require the most immediate attention.

They said understanding which species are at risk can also help identify what factors might be most responsible for the rising extinction rates.

Among other actions, the researchers propose a global agreement to ban the trade of wild animals. They argue the illegal capture or hunting of wild animals for food, pets and medicine is a “fundamental ongoing threat” not only to species facing imminent decimation, but also to human health.

The researchers said Covid-19, which is thought to have originated in bats and then been transmitted to humans through another creature in a live animal market, is an example of how the wildlife trade can have considerable implications for humans.

They point out that wild animals have transmitted many other infectious diseases to humans and domestic animals in recent decades due to habitat encroachment and wildlife harvesting for food.

“It’s up to us to decide what kind of a world we want to leave to coming generations – a sustainable one, or a desolate one in which the civilisation we have built disintegrates rather than builds on past successes,” said study coauthor Peter Raven, president emeritus of the Missouri Botanical Garden.

The research is published in the Proceedings of the National Academy of Sciences.

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