Humans and climate change have driven the woolly rhinoceros to extinction | The science

It was what the military calls an enveloping maneuver. After 2.5 million years of living throughout Eurasia, including the Iberian Peninsula, the woolly rhinoceros (Celodonta antiquitatis) retreated further east and further north, pursued by bad weather and finished off by Neanderthals and, especially, modern man. Eventually, when the ice age passed and the planet entered the modern era, as did the mammoths and most of the megafauna, only a few remained in the far northeast of Siberia. They did not cross the Bering Strait to America; they died out earlier. Now modeling of this retreat has allowed the blame to be distributed: climate fluctuations made its coffin, and human hunting hammered the nails. The study authors believe that four of the five remaining rhino species are also on the path to extinction. But they have several ways out.

The extinction of most megafauna (broadly speaking, animals weighing more than 1,000 kilograms) of the late Pleistocene is one of the biggest mysteries that has complicated the lives of paleontologists. Mammoths, glyptodonts, mastodons, woolly rhinoceroses, cave bears… and so on, up to 65 species existed long before the start of the last ice age (about 126,000 years ago). They were still on Earth when modern humans began their expansion from Africa and reached Western Europe about 55,000 years ago. For thousands of years, Neanderthals, sapiens, and various large species, both megaherbivores and carnivores that would make a lion a big cat, shared the space. But at the end of this period, the end of which was marked by the end of glaciation, about 12,000 years ago, giving way to the warm Holocene period, one could count on one hand the species of large animals that survived. Today, leaving aside the European and American bison, only hippopotamuses, elephants and rhinoceroses remain in Africa, and the remaining two species in South Asia. Studying the woolly rhino could help us learn what happened to other extinct rhinos and what awaits those who remain.

Researchers from several European, Australian and Chinese universities collected hundreds of references to woolly rhinoceros remains (either in the fossil record, in bone form, or in their ancient DNA) over the past 52,000 years to create a model that also included the evolution of Eurasian climate (this animal lived from the Iberian Peninsula to the extreme east of Asia). They concluded it with the presence of Neanderthals in the fossil record and the progressive settlement of the area by modern humans. The dating and location of each record allowed them to draw a dynamic map of the evolutionary distribution of these rhinoceroses. Map and all works published in a scientific journal PNAS, shows that climate change did not kill them as the Tyrians claim. Neither did other human species, the Trojans claim. Both.

“We gave it a blow, but it was a species that was already very sick, it had entered a negative, recessive dynamic, mainly due to climate change,” says professor at the University of Copenhagen (Denmark) and co-author from the studio of David Nogues . When modern humans arrived and spread across Eurasia in the middle of the Ice Age, they included megaherbivores such as the mammoth and woolly rhinoceros in their diet. But the fossil record does not reveal significant declines in animal populations until many millennia later. “We find differences as the planet approaches maximum glaciation,” he adds. The last ice age, called the Wurm Glaciation, had a cold peak between 26,000 and 20,000 years ago, when ice in the northern hemisphere fell to the top of what is now the United States and in Europe as far away as Germany. And further south there are hundreds of kilometers of permafrost. “What happened to ecosystems is that plant productivity fell. This meant there was less food for the herbivores,” adds Noguez.

The coffin was already ready. Rhinoceroses are disappearing from Europe and almost all of Siberia, limited to the southern strip of Siberia, the Tibetan Plateau and, in the far north, Beringia. The fossil record also indicates increasing consumption of the animal by modern humans, who included arrows and other projectiles in their hunting weapons in addition to spears. Damien Fordham, professor at the Institute of the Environment at the University of Adelaide (Australia) and first author of the study, summarizes this: “About 30,000 years ago, a combination of cold temperatures and low but steady levels of hunting caused woolly rhinoceroses to spread southward, trapping them in isolated and rapidly deteriorating habitats.” habitat until the end of the Ice Age.”

“As the Earth thawed, woolly rhino populations were unable to colonize the new habitats that were opening up in northern Eurasia.”

Damien Fordham, Professor, Institute of the Environment, University of Adelaide, Australia

But the coffin lid was exposed to the weather, this time in the opposite direction. After the glacial maximum, a slow warming begins, lasting about 10,000 years. The ice retreated, freeing up large areas that were once again available to megaherbivores. “As the ground thawed and temperatures rose, woolly rhinoceros populations were unable to colonize the new habitats that were opening up in northern Eurasia, leading to the destabilization and collapse of their populations, leading to their extinction.” The authors admit they don’t know exactly what happened, but woolly rhinoceroses no longer appear in the fossil record in much of the area they once occupied. Here they introduce elements of ecological theory to explain this: the remaining groups were in a fragmented habitat, isolated. From what is known about living rhinos, their mobility is very limited, and due to fragmentation, genetic exchange between populations is reduced, which must reduce their ability to adapt to environmental changes. And with each generation, the number decreased due to hunting.

The last woolly rhinoceroses survived, like mammoths, in the far northeast, on the Asian side of the Bering Strait. During the Glacial Maximum, Beringia remained relatively ice-free and became a climatic refuge. But the species was already doomed. The last specimens of this species became extinct just over 9,000 years ago.

“The highway that drove the woolly rhino to extinction is where the rest of the rhinos live.”

David Nogues, researcher at the University of Copenhagen, Denmark

“Extinction is not the extinction of the last individual. It’s not an event, it’s a process,” Nogues emphasizes. “There are different roads leading to extinction. There is more than one, but we know that the same processes that led to the extinction of the woolly rhinoceros led to the extinction of the woolly rhinoceros, along with other rhinoceros species: habitat fragmentation, hunting, the inability of populations to unite. …”, he adds. And this happens in the black rhinoceros and three Asian species. The northern white subspecies is almost extinct: only two specimens remain in captivity. But the Spanish researcher also emphasizes that there is a factor in this case that was not present in the past : man’s awareness of his responsibility and his ability to provide an alternative to these animals that seem to come from prehistoric times: “There is a species, the white rhinoceros, whose southern population a hundred years ago barely numbered 100 animals, but now numbers more than 18,000 specimens. This is one. of the classic examples that with an investment of money, will, resources, funds and political decisions, you can restore the natural world.”

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