The recalibrated Greenland record (black line) calculated from the combined Cariaco-Greenland chronology (Table S4) was used to generate a 500-year running window calculating the coefficient of variation (δ18O CV) to highlight periods of likely rapid environmental change, highlighting the impacts at the onset and ending of interstadials, and relationships to the megafaunal transition events. The timing of interstadials is shown according to the recalibrated Greenland record, with the pink bars below representing the error margins (1 sd) for the estimated onset of GI events in the GICC05 chronology. Graphic: Cooper, et al., 2015 / Science Magazine

By Laura Geggel
25 July 2015

(LiveScience) – The mighty megafauna of the last ice age, including the wooly mammoths, short-faced bears and cave lions, largely went extinct because of rapid climate-warming events, a new study finds.

During the unstable climate of the Late Pleistocene, about 60,000 to 12,000 years ago, abrupt climate spikes, called interstadials, increased temperatures between 7 and 29 degrees Fahrenheit (4 and 16 degrees Celsius) in a matter of decades. Large animals likely found it difficult to survive in these hot conditions, possibly because of the effects it had on their habitats and prey, the researchers said.

Interstadials "are known to have caused dramatic shifts in global rainfall and vegetation patterns," the study's first author Alan Cooper, director for the Australian Centre for Ancient DNA at the University of Adelaide in Australia, said in a statement emailed to Live Science.

Temperature drops during the Late Pleistocene showed no association with animal extinctions, Cooper said. Instead, only the hot interstadial periods were associated with the large die-offs that hit populations (local events) and entire species of animals (global events), he said.

Ancient humans also played a role in the megafaunal extinction, albeit a smaller one, he said. By disrupting the animals' environments, human societies and hunting parties likely made it harder for megafauna to migrate to new areas and to refill areas once populated by animals that had gone extinct, he said. […]

They examined DNA from dozens of megafaunal species that lived during the Late Pleistocene, combing through more than 50,000 years of DNA records for extinction events. The ancient DNA not only told them about global extinction events, but also local population turnovers, which occur when a group of animals dies and another population of animals moves in to replace them. [Wipe Out: History's Most Mysterious Extinctions]

They then compared the data on megafauna extinction with detailed records of severe climate events, which they gathered from Greenland ice cores and the sedimentary record of the Cariaco Basin off Venezuela.

"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." […]

"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.

In addition, humans have disrupted the habitats and surrounding areas of many wild animals, making it challenging for species to migrate or shift ranges to places where they would be better adapted to deal with climate change, he said. […]

"This study is a bit of a wake-up call," said Eline Lorenzen, an assistant professor of paleogenetics at the University of Copenhagen in Denmark. "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.” [more]

Mighty Mammoths Fell Prey to Rapidly Warming Earth

ABSTRACT: The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers. Here, we compare ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions/replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement/extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions prior to the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts.

Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover



Blog Template by Adam Every . Sponsored by Business Web Hosting Reviews