If current conservation efforts are not dramatically increased, the vast majority of large mammal species will disappear over the next five decades, say European scientists, who also believe that nature would need 3 to 5 million years to recover from the destruction of biodiversity.
Earth is in the midst of its sixth mass extinction, according to a new study.
Since the first traces of fossil life on Earth, about 540 million years ago, the species have experienced five severe extinction crises, during which more than 75% of them have disappeared.
However, unlike the current one, the other large waves of animal extinctions have been on a much longer geological time scale, millions of years.
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The most brutal extinction, the most recent, was triggered in the Cretaceous, some 65 million years ago, presumably when an asteroid of about 15 km fell on Earth, in the present Yucatan Peninsula, Mexico. The collision was of a power equivalent to 1 billion atomic bombs. Consequence: 76% of species would have disappeared, especially dinosaurs.
However, the current extinction is happening very quickly and has only one origin … the human.
The impact of Homo sapiens on its environment can be observed up to 8000 years ago in China, where evidence of deforestation has been observed.
It has since destroyed thousands of ecosystems, over exploited the planet’s resources, polluted, propagated microbes, viruses and invasive species. An intense activity that is currently leading to an episode of global warming that he would be responsible for.
In 2015, an international study showed that vertebrates disappear at a rate up to 114 times higher than normal. It showed that 80 of the 5,570 listed mammal species have disappeared in the last 500 years.
The big losers
In the present work, scientists from the Danish universities of Aarhus and Gothenburg believe that the animal and plant extinction currently observed is happening so fast that evolution has failed to adapt to it.
According to paleontologist Matt Davis and his colleagues, at this rate, most mammal species will be gone in 50 years. They also established that if mammals diversify at their normal rate, they will need:
- 5 to 7 million years to recover to a level similar to that which existed before modern humans appeared;
- 3 to 5 million years to reach current levels of biodiversity.
In the past, after each massive extinction, evolution has slowly replaced animal and plant losses with new species.
Mammals more fragile
To arrive at this estimate, the researchers used a vast database on mammals, which includes not only the species that exist today, but also the hundreds of species that have lived in the recent past and have disappeared. as a result of the rise of Homo sapiens.
Using this information, the authors of this study published in the journal PNAS (English) were able to measure the complete impact of our species on other mammals.
The disappearance of certain species is sometimes more significant for science. For example, the extinction of the Australian marsupial lion ( Thylacoleo ) 46,000 years ago is associated with the disappearance of a distinct evolutionary line, since the animal had no close relatives.
Thus whole branches of the evolving tree of life disappear, and with them unique ecological functions and the millions of years of evolution they represented.
Large mammals, such as giant sloths and saber-toothed tigers, which disappeared about 10,000 years ago, were very distinct in evolutionary terms. Since they had few close relatives, their disappearance caused whole branches of the evolutionary tree of the Earth to be cut off.
“There are hundreds of species of shrews, so they can survive a few extinctions. There were only four species of saber-toothed tigers, and they all disappeared, “says the paleontologist.
Prioritize species to save
Critically endangered species, such as the black rhinoceros, are at risk of extinction in the coming decades. According to the researchers, the Asian elephant, one of only two surviving species of a mammalian order (proboscidians, from the Greek proboski meaning “trunk”), which once included mammoths and mastodons, has less a 33% chance of surviving this century.
Nature is becoming poorer with the disappearance of large wild mammals.
The present works, however, suggest that all is not lost. The authors believe that their data can be used to identify endangered species that are evolutionarily distinct in order to prioritize conservation efforts and thus prevent their extinction.
“It’s a lot easier to save the current biodiversity than to recreate it later,” concludes Matt Davis.
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