Woolly mammoths killed by global warming

Woolly mammoths were remorselessly hunted and faced an increasingly warm world Scientists claim they have solved the great ‘zoological puzzle’ of the woolly mammoth’s extinction - claiming the demise was down to man’s hunting and global warming. It was previously thought ice-age mammals including the mammoth, woolly rhino and giant sloths were wiped out by extensive human hunting.
Other experts argued the extinction was due to a decline of their grassland habitats and the spread of inhospitable forests as the ice began to thaw.
Now scientists say they can calculate exactly which factor had the biggest impact, after comparing the earth’s temperature and the arrival of modern humans over the last 100,000 years.
Graham Prescott, PhD student at Cambridge University and co-author of the paper, said the findings may provide a valuable lesson as to the fate of species such as tigers, polar bears, elephants and rhinos.
He said: ‘Most extinction happened in the last 100,000 years so we split those years into ten blocks of ten to analyse the changes in population and climate more closely.
‘Our research shows that extinction of many large animals in the past cannot be explained by just human pressure or climate change. It must be a combination.
‘Many large, charismatic animals today are threatened by both hunting pressure and changes in climate.
‘If we do not take action to address these issues we may see further extinction.
‘And in contrast to the people who first encountered these megafauna, people today are fully aware of the consequences of our actions.
‘This gives us hope that we can prevent future extinction, but will make it all the worse if we do not.’
The researchers used data from an Antarctic ice core, which gives one of the longest running records of changes in the earth’s climate.
They also compiled information on the arrival of modern humans from Africa on five different land masses - North America, South America, most of Eurasia, Australia and New Zealand.
The scientists conducted a statistical analysis using both climatic information and the timing of arrival of modern humans from the late Quaternary period - from 700,000 years ago until present day - focusing on the last 100,000 years.
They assessed the relative importance of different factors in causing the extinction of many of the world’s terrestrial megafauna - animals 44 kg or larger.
These extinction included mammoths in North America and Eurasia, mastodons and giant sloths in the Americas, the woolly rhino in Europe, giant kangaroos and wombats in Australia, and the moas (giant flightless birds) in New Zealand.
In the paper entitled ‘Quantitative global analysis of the role of climate and people in explaining late Quaternary megafaunal extinction’, researchers determined it was a combination of factors that caused the extinction.
David Williams, Cambridge University PhD student and co-author said the research has helped solve a long-running ‘zoological puzzle.’
He said: ‘The loss of these animals has been a zoological puzzle since the time of Charles Darwin and Alfred Russel Wallace.
‘At that time, many people didn’t believe that human-caused extinction was possible, but Wallace argued otherwise.
‘We have now shown, 100 years later, that he was right, and that humans, combined with climate change have been affecting other species for tens of thousands of years and continue to do so.
‘Hopefully, now though, we are in a position to do something about it.’
Professor Rhys Green, from the RSPB and co-author of the paper, added: ‘The key difference this time is that the climate change is not caused by fluctuations in the earth’s rotation axis but to warming caused by fossil fuel burning and deforestation by humans - a double whammy of our own making.
‘We should learn the lesson and act urgently to moderate both types of impact.’
The findings were published in the journal Proceedings of the National Academy of Sciences today.