Ozone loss may have caused mass extinction
Pinus mugo in the French Pyrenees. Image: By Sébastien D’ARCO, via Wikimedia Commons
The loss of ozone may have caused the extinction many millions of years ago of most life on Earth, scientists believe.
LONDON, 21 February, 2018 – Californian scientists have found a new way to account for extinction and to explain mass murder on a planetary scale.
Seven out of 10 land animals perished at the end of the Permian, 252 million years ago. So did 95% of marine species. And the deadly factor at work may have been the destruction of atmospheric ozone, the protective screen in the stratosphere that eliminates harmful ultraviolet light.
Jeffrey Benca of the University of California Berkeley and colleagues report in the journal Science Advances that they irradiated a series of dwarf pines with doses of ultraviolet-B radiation up to 13 times stronger than any on Earth today.
They used 60 pines of the species Pinus mugo, irradiated them for 56 days, and then spent three years examining 57,000 pollen grains produced over that period.
UV-B wavelengths are associated with mutations in DNA, the inheritance mechanism of all life on Earth. The dose chosen was the one to which creatures might have been exposed at the close of the Permian period, an episode characterised by immense volcanic eruptions that would have damaged the upper atmosphere.
Exposed to sterility
And, the researchers found, after two months exposure, the trees survived, but at a cost: they had become sterile. Their cones shrivelled within days of emerging. Once restored to present day, open air conditions, the pines all recovered.
Plants underwrite all animal life: repeated bouts of forest sterility could, researchers think, have played a role in the collapse of the planet’s biosphere.
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