Hyperthermal-driven mass extinctions: killing models during the Permian-Triassic mass extinction

Many mass extinctions of life in the sea and on land have been attributed to geologically rapid heating, and in the case of the Permian-Triassic and others, driven by large igneous province volcanism. The Siberian Traps eruptions raised ambient temperatures to 35-40 degrees C. A key question is how massive eruptions during these events, and others, could have killed life in the sea and on land; proposed killers are reviewed here. In the oceans, benthos and plankton were killed by anoxia-euxinia and lethal heating, respectively, and the habitable depth zone was massively reduced. On land, the combination of extreme heating and drought reduced the habitable land area, and acid rain stripped forests and soils. Physiological experiments show that some animals can adapt to temperature rises of a few degrees, and that some can survive short episodes of increases of 10 degrees C. However, most plants and animals suffer major physiological damage at temperatures of 35-40 degrees C. Studies of the effects of extreme physical conditions on modern organisms, as well as assumptions about rates of environmental change, give direct evidence of likely killing effects deriving from hyperthermals of the past. This article is part of a discussion meeting issue 'Hyperthermals: rapid and extreme global warming in our geological past'.