Paleobotanists put dwarf, bonsai pine trees in growth chambers and subjected them to up to 13 times the UV-B radiation Earth experiences today, simulating conditions that likely existed 252 million years ago during the planet’s worst mass extinction. The UV-B made the pines temporarily sterile and created malformed pollen, evidence that ozone depletion from volcanic eruptions could have led to high UV-B levels that contributed to the end-Permian crisis for plants and animals.
