Climate - Extinctions

Volcanoes are thought to have had a strong influence on climate at the end of the Permian. About 250 million years ago, extensive Siberian flood basalt (Siberian Traps) erupted in northeast Siberia and western China. This eruption released large quantities of volcanic ash into the atmosphere, darkening the sky and reducing the efficiency of plants to take up atmospheric carbon dioxide through photosynthesis.

During this period, shallow-water warm-water invertebrates exhibited the longest and largest extinctions. Starting from a maximum number of genera in the middle Permian, the extinction of these invertebrates declined to 12-70% by the beginning of the Capitanian. The diversity of these invertebrate groups was at an all-time low during the Permian. The extinctions in the Middle and Late Permian were even more severe, with catastrophic declines of 70 to 80 percent.

Catastrophic changes in the ecosystem have reduced marine invertebrates to a critical level, the lowest diversity since the end of the Ordovician. The last Permian extinction event, sometimes referred to as the Permian Crisis, although realistic, is likely to have taken 15 million years to occur and wiped out many ecologically challenging faunas that were already greatly reduced by earlier extinctions.

While other single event causes have been proposed, current explanations of the Permian extinction event focus on how the trophic cycle was disrupted by biological and physical causes. In particular, the hypothesis of a temperature crisis occurring in shallow waters is based on studies of oxygen isotopes and the calcium-magnesium ratio in Permian shell fossils.