If we continue along our present path, we’re heading towards an inevitable sixth mass extinction, a period that future geologists will mark in Earth’s history. Scientists have identified five major mass extinction events in the past, each wiping out at least three-quarters of life. But with human activities such as habitat destruction, species extermination, and climate change, are we currently in the midst of the sixth mass extinction?
Many researchers argue that the sixth mass extinction is already underway, with some describing it as “biological annihilation” and “mutilation of the tree of life” in their studies. However, there are differing opinions, with some claiming that the mass extinction hasn’t yet commenced.
Robert Cowie, a research professor at the University of Hawaii, emphasized that a mass extinction cannot be declared until it has actually occurred — when 75% of species have vanished. According to a 2022 study led by Cowie and published in Biological Reviews, only up to 13% of known species have gone extinct since 1500, falling far below the 75% threshold.
“It hasn’t happened yet,” Cowie stated.
While some projections suggest we may hit the 75% threshold within 10,000 years, other studies indicate it could occur within a few centuries, or even sooner if conditions deteriorate. Mass extinctions typically unfold within a relatively short geological timeframe of less than 2.8 million years, a span easily encompassing the centuries to millennia it might take to reach the mass extinction threshold. Thus, researchers argue that the event may already be underway based on these predictions.
“We are witnessing the sixth mass extinction in real-time,” asserted Anthony Barnosky, a professor emeritus of integrative biology at the University of California, Berkeley.
Studies indicate that species are currently disappearing at a rate between 100 and 1,000 times faster than the normal background rate of extinction, calculated from the fossil record. Barnosky warned that this rate may accelerate as we further degrade the planet.
Barnosky also pointed out that the extinction rate of species might obscure the rapid decline in wildlife populations. We often don’t declare a species extinct until the last individual has vanished, and conservation efforts may artificially prolong the survival of species that are already critically endangered.
“We have decimated almost 70% of the planet’s wild animals since my birth,” Barnosky lamented. “Clearly, this trend cannot continue without ushering in the sixth mass extinction.”
A 2022 WWF report revealed that monitored vertebrate populations plummeted by an average of 69% between 1970 and 2018, with Latin America experiencing the most significant regional decline at 94%. Moreover, this figure excludes the numerous invertebrate species.
Although data on invertebrate decline is sparse, certain groups have suffered staggering losses. For example, a 2015 study co-authored by Cowie highlighted the drastic decline of Hawaii’s Amastridae snails due to invasive species and habitat destruction. Out of the 282 historically known species, researchers could only confirm the survival of 15. “That’s indicative of a mass extinction event,” Cowie remarked.
While the state of biodiversity and the impending mass extinction are dire, Barnosky believes it’s not too late to save most species from extinction and avert the sixth mass extinction threshold.
“Although we’re losing populations and species at an alarming rate, we haven’t yet reached the point of no return,” Barnosky asserted. “We still have an opportunity to reverse course, but time is running out rapidly.”