Scientists have documented Five main Mass extinction events in Earth's history, during which at least three-quarters of living organisms became extinct. But with humans removing natural habitats, wiping out species and changing the climate, are we now in a sixth mass extinction situation?
Many researchers claim that a sixth mass extinction is underway, and one team described “Biological extermination” And “Distortion of the tree of life” in their scientific studies. However, others argue that Mass extinction has not yet begun.
Robert CoyThe University of Hawaii research professor told Live Science that, strictly speaking, you can't declare a mass extinction until it actually happens, once 75% of species have disappeared.
A 2022 study led by Cui and published in the journal Biological reviews It is estimated that up to 13% of known species have become extinct since 1500, well below the 75% mass extinction threshold.
“That hasn't happened yet,” he said.
Some researchers have estimated that we will reach the 75% threshold within 10,000 years, while other studies have concluded that we could reach this dismal milestone in 2018. Only a few centuries – With potentially a shorter time frame if things get worse.
Related: Scientists have just discovered a sixth mass extinction hidden in Earth's ancient past
Mass extinctions occur over a short geological period of less than 2.8 million years, according to scientists' estimates Natural History Museum in London. The centuries to millennia it would take to reach the mass extinction threshold fall within this time frame. So, if these estimates are taken to be predictive, researchers can say that the event has already begun.
“We are witnessing the sixth mass extinction in real time.” Anthony BarnoskyA professor emeritus of integrative biology at the University of California, Berkeley, told Live Science in an email.
Studies have estimated that species are currently going extinct at a rate 100 to 1,000 times faster than the natural rate of extinction, which is calculated based on the time a species evolved and went extinct in the fossil record. “I think the rate will go up as more of the planet is destroyed,” Cui said.
Barnoski noted that the rate of species extinction may mask the rapid decline in wildlife populations because we do not consider a species to be extinct until the last individual disappears. Species are often declared extinct decades after they were last seen in the wild, while others persist with conservation measures when most of their populations have died.
“We've killed roughly 70 percent of the wild animals on the planet since I was born,” Barnoski said. “Clearly this cannot continue for much longer without making a sixth mass extinction a reality.”
A 2022 WWF report It found that observed numbers of vertebrate mammals, birds, amphibians, reptiles and fish declined by an average of 69% between 1970 and 2018. This number is a global average; Latin America recorded the highest regional decline of 94%. In addition, this number does not include the most numerous invertebrate species.
There is no data on declines in invertebrate populations, but some groups have suffered staggering losses. For example, a 2015 study co-authored by Cowie was published in the journal Protecting the living He highlighted the decline of Amastridae snails in Hawaii due to invasive species and habitat loss. Of the 282 species that historically inhabited Hawaii, researchers have only been able to confirm that only 15 species are still alive. “This is a mass extinction,” Coy said.
Barnoski described the destruction of biodiversity and the booming mass extinction as “bad news.” But he said it is not too late to save most of the species heading towards extinction and thus prevent us from reaching the sixth mass extinction threshold.
“Although we are annihilating populations and species at an astonishing speed, we are not done yet,” Barnoski said. “We still have a chance to turn things around, but the window of opportunity is closing quickly.”
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