Earth’s broiling past preserved in pollen

Abstract

Chemical clues in fossilized pollen grains suggest that the world’s greatest mass extinction was a sunny affair, according to a new analysis ( Sci. Adv. 2023, DOI: 10.1126/sciadv.abo6102 ). As the Permian period gave way to the Triassic about 250 million years ago, massive volcanic eruptions in present-day Siberia triggered a cataclysmic combination of greenhouse gas emissions, widespread mercury pollution, and a host of other atmospheric disturbances. Yet the full picture remains murky, including the possibility that damage to the ozone layer may have cooked many of the species already struggling to survive concurrent calamities, says Wesley T. Fraser, an organic geochemist at Oxford Brookes University. To investigate, Fraser and his colleagues looked at tiny grains of fossilized pollen from southern Tibet. This collection contains around 800 pollen grains that come from the ancient relatives of ferns and conifers—plant types that survived the extinction event—and date back to time points