Dr Claire Belcher of UCD School of Biology and Environmental Science, seen here inside the purpose-built chamber, wearing a breathing apparatus
New research findings by scientists from the UCD School of Biology and Environmental Science question one of the theories behind a series of mass extinction events including a catastrophe that wiped out almost 95% of all species on earth.
Many scientists suspect that the worst of all five of the mass extinctions, the Permian-Triassic event 250 million years ago, was the result of a comet or an asteroid colliding with the earth. Others believe that flood volcanism from the Siberian Traps and the associated oxygen loss in the seas was the cause. While others continue to investigate the possibility that thinning levels of atmospheric oxygen caused the eradication of so many species at the time.
But new research findings by Dr Claire Belcher and co-author Dr Jennifer McElwain, recently published in Science, question the theory of falling oxygen levels as a mechanism for causing the mass extinction events.
To assess the likely atmospheric oxygen levels at the time of the mass extinction events, Dr Claire Belcher and her UCD colleagues spent several months measuring the lower limits of oxygen at which combustion can occur.
“By performing experimental burns using pine wood, moss, matches, paper and a candle at 20°C in varying ranges of oxygen concentrations and comparing these results to the occurrences of fossil charcoal throughout the Mesozoic (250-65 million years ago), we were able to identify that prolonged periods of low oxygen are unlikely to have occurred,” says Dr Belcher.
“Low oxygen atmospheres, less than 12%, are considered to be the primary driver of at least two of the ‘big five’ mass-extinction events,” explains Dr Belcher. “But our research findings question that hypothesis and highlight the need for more detailed studies of fossil charcoal across these mass extinction events.”
This is the first time that research to identify the lower limit of atmospheric oxygen under which combustion can occur have been conducted within fully controlled and realistic environments. The six walk-in chambers at UCD, funded by EU Marie Curie, enable the realistic reconstruction of environmental conditions from the past.
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