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Hot water and hypoxia: 'The Great Dying's' greatest killers

American Association for the Advancement of Science

Increased marine temperatures and reduced oxygen availability were the specific environmental features responsible for the extinctions of vast swaths of ancient ocean life -- nearly 96% of all marine species -- during the catastrophic end-Permian mass extinction event, a new study finds. The study further predicts a novel pattern of extinction risk during this time, with lower rates of extinction in the tropics than in high latitudes, highlighting the potential for this pattern in future extinction events triggered by similar environmental changes, some of which are already underway. In a related Perspective, Lee Kump writes: "As our understanding of the drivers and consequences of end-Permian climate change and mass extinction improves, the lessons for the future become clear." Nearly 252 million years ago, intense volcanic activity belched massive volumes of greenhouse gasses into the atmosphere and triggered rapid changes to the climate, which resulted in "the Great Dying" -- the largest mass extinction event in Earth's history. Previous research has suggested that rapid climate change resulting from volcanic activity likely triggered the widespread collapse of biodiversity. However, how each of the resulting environmental impacts contributed to the extinction remains unclear. Justin Penn and colleagues investigated the roles of rapid greenhouse warming and the accompanying loss of oxygen in the ocean, the two best-supported aspects of end-Permian environmental change, according to the authors. Penn et al. investigated the dynamics of the ancient extinction using an Earth system model coupled with data representing a diverse collection of living species to simulate the effects of end-Permian ocean warming and deoxidation on habitat loss and animal survival. The results revealed distinct patterns of extinction -- animals that lived in higher latitudes were more prone to extinction. As waters warmed and oxygen became scarce, their low tolerance for hypoxic environments meant they had nowhere to run. Tropical marine animals, pre-adapted to low-oxygen and high temperatures, were better-equipped to survive the environmental changes, according to the authors.


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