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

Abstract

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°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°C. However, most plants and animals suffer major physiological damage at temperatures of 35–40°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’.

The base of the Lystrosaurus Assemblage Zone, Karoo Basin, predates the end-Permian marine extinction

“…4). Hence, interpretations about behavioral [48][49][50] , physiological [50][51][52] , biogeographical 53 , extinction mechanisms 54 , and life-strategy patterns [55][56][57] of the Lystrosaurus AZ tetrapods do not reflect a response to, or consequence of, the terminal marine crisis. Yet, our high precision age determination from the Nooitgedacht section and corresponding palynological record does conform with recent findings in eastern Australia 6 .…”

Placing our current ‘hyperthermal’ in the context of rapid climate change in our geological past

“…Whereas, on land, plants and animals struggled to cope with the heat shock as a consequence of mean annual temperatures reaching greater than 35-40°C and were likely tipped over the edge by the combined effects of warming, acid rain and aridity. Notably, Benton [50] suggests that these similar kill mechanisms were operative during the other hyperthermal events listed in table 1, albeit at a reduced magnitude.…”

“…By contrast, the hyperthermal at the P-T boundary was associated with the most severe terrestrial and oceanic mass extinction of the last 541 Myr (the Phanerozoic), where 96% of species became extinct-earning the event its alternative name 'the great dying' (table 1). The smorgasbord of killmechanisms responsible for such an enormous level of extinction at the P-T boundary is reviewed here by Benton [50]. In the oceans, poster species of the Palaeozoic, such as rugose coral, crinoids and trilobites, were most probably wiped out by ocean anoxia and euxinia and lethal levels of warming, all serving to squeeze the habitable zone in the ocean out of existence.…”

Ancient plants escaped the end-Permian mass extinction

“…So far, this is the most comprehensive database generated for floral analysis before and after the end-Permian crisis. It amasses the evidence that has been considered by many palaeontologists to indicate a trend in mass extinction of terrestrial plants that mirrors that of the marine mass extinction 9 .…”

“…See Letters p.66, p.71, p.76 & p.81 species between the Permian and the end of the Middle Triassic (between 251.9 million and around 237 million years ago) has focused on the effects of a global trend towards aridification. It was proposed that, after a worldwide collapse of plant communities and a mass extinction of species that cascaded through the food chain 9 , there was a change in the floral species across global landscapes by the Middle Triassic period. For the demise of Glossopteris, Fielding and colleagues find no evidence of an aridification trend in their region that would suggest that a hot terrestrial landscape promoted a mass extinction of plants during the time of the end-Permian crisis.…”