Ancient ozone holes may have sterilized forests 252 million years ago | Science News

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Ancient ozone holes may have sterilized forests 252 million years ago

Barren trees could have collapsed food webs, leading to Earth’s greatest mass extinction

By
7:00am, February 12, 2018
dwarf pines

BARREN TREES  Modern dwarf pines (shown) become unable to reproduce when irradiated by ultraviolet-B lamps. A similar fate may have befallen forests 252 million years ago, when massive bursts of volcanic gases likely weakened Earth’s ozone shield.

Volcano-fueled holes in Earth’s ozone layer 252 million years ago may have repeatedly sterilized large swaths of forest, setting the stage for the world’s largest mass extinction event. Such holes would have allowed ultraviolet-B radiation to blast the planet. Even radiation levels below those predicted for the end of the Permian period damage trees’ abilities to make seeds, researchers report February 7 in Science Advances.

Jeffrey Benca, a paleobotanist at the University of California, Berkeley, and his colleagues exposed plantings of modern dwarf pine tree (Pinus mugo) to varying levels of UV-B radiation. Those levels ranged from none to up to 93 kilojoules per square meter per day. According to previous simulations, UV-B radiation at the end of the Permian may have increased from a background level of 10 kilojoules (just above current ambient levels) to as much as 100

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