Carbon Dioxide Responsible for Permian Mass Extinction?
When the word extinction is mentioned, most people think of the extinction of the dinosaurs that occurred 65 million years ago. But, in fact, there have been several other extinctions in the history of life on Earth, most of which are far more extensive, in terms of the number of species that disappeared, than the extinction of the dinosaurs. About 250 million years ago, around 90 percent of the animal species on Earth disappeared in the mass extinction during the Permian Era. Although very few fossils and sediments from this time remain, scientists have proposed theories to explain the cause of this mass extinction. One of the most recent theories claims the cause to be a huge increase in atmospheric and dissolved carbon dioxide.

Although normally harmless, carbon dioxide can cause asphyxiation if too much is around. In 1986, water rich in carbon dioxide gas erupted out of a lake in Africa, produced a carbon dioxide mist, and killed 1,000 people as well as animals near the lake. In Permian times, the escape of carbon dioxide would have been much more gradual, and scientists are not suggesting that asphyxiation occurred on a worldwide scale. However, an increase in atmospheric carbon dioxide may have caused global warming and a global destruction of habitats and animals. Plate tectonics, asteroid impacts, and volcano eruptions have been suggested as causes or contributors to the increased release of carbon dioxide 250 million years ago. Some scientists believe that the carbon dioxide theory explains the patterns of extinction and carbonate sediments better than any other theory.

"Mass Extinction of Permian Era Is Linked to Carbon Dioxide," New York Times, July 30, 1996