Past extinctions linked to prehuman global warming

The wooly mammoths of the last ice age are thought to have become extinct due to a series of rapid climate-warming events.

A new study suggests that the megafauna of the last ice age which included cave lions, short-faced bears and mammoths all died out because of weather. Studies show that temperatures increased between 7 and 29 degrees Fahrenheit over only a few decades.

Between 60,000 to 12,000 years ago, these spikes, known as interstadials, caused large animals to struggle to survive in the hot conditions due to the effects it not only had on them physically, but on their habitats and prey as well, according to Discovery News.

The study’s first author, Alan Cooper, said that interstadials “are known to have caused dramatic shifts in global rainfall and vegetation patterns.”

The temperature drops during the Late Pleistocene provided no link with animal extinction. Cooper said that instead, it was the hot interstadial periods that were more closely associated with the large losses that affected entire species of animals.

Coop, director for the Australian Center for Ancient DNA at the Unvirsity of Adelaide in Australia said that ancient humans played a pretty big role in the megafaunal extinction. During those times, while disrupting the animals’ environment, human communities as well as hunting parties made it harder for megafauna to migrate away to new areas and to refill the areas that were once full of animals that had by then, gone extinct.

French paleontologist George Curview in 1796 first speculated that the giant biblical floods were to blame for the animals’ demise. Charles Darwin as well was baffled after he came across megafaunal remains in South America.

But since then there have been many studies that have held the responsibility to ice age humans, temperature changes and a perfect storm of certain events. But with further investigation, and with advancements in technology, Cooper was able to examine ancient DNA and study ancient climate in order to come to a more substantial conclusion.

By examining the DNA from dozens of megafaunal species from the Late Pleistocene time, they found new information about global extinction events including local population turnovers which happens when a group of animals dies and then another group populates to replace them.

The data they found was then compared with detailed records of severe climate events.

“By combining these two records, we can place the climate and radiocarbon dating data on the same timescale, thereby allowing us to precisely align the dated fossils against climate,” Cooper said. “The high-resolution view we gained through this approach clearly showed a strong relationship between warming events and megafaunal extinctions.”

The team also found that the extinction events were staggered over time and space because the interstadial warming had different effects on different areas.

Today, the Earth’s climate is found to be more stable than it was during the Late Pleistocene. Researchers are very worried about the world’s current warming trends though.

“In many ways, the rise of atmospheric carbon dioxide levels and resulting warming effects are expected to have a similar rate of change to the onset of past interstadials, heralding another major phase of large mammal extinctions,” Cooper said.

Humans have also disrupted the surrounding areas and habitats of many wild animals today making it hard for those species to migrate to other areas that they would be better adapted to in order to deal with climate changes.

The new study shows “that the extinction and population turnover of many megafauna was associated with rapid warming periods, rather than the last glacial maximum [when the ice sheets reached their maximum during the last glacial period] or Younger Dryas [a sudden, cold spell that happened when the Earth was starting to warm] as has previously been suggested,” said Eline Lorenzen, an assistant professor of paleogenetics at the University of Copenhagen in Denmark.

He also said that it is the understanding of how past climate changes affected extinction rates that can help people today better prepare for rapid global warming.

“This study is a bit of a wake-up call,” Lorenzen said. “Here we have empirical evidence — based on data from a lot of species — that rapid climate warming has profoundly impacted megafauna communities, negatively, during the past 50,000 years.

“It doesn’t bode well for the future survival of the world’s megafauna populations,” she said.



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