Permian-Triassic mass extinction was caused by ocean acidification

New findings of scientists from several universities published in Science show that the Permian-Triassic mass extinction (~ 252 million years ago), the greatest extinction event of all time, was caused by ocean acidification. The researchers studied boron isotopes from marine sediments in order to reconstruct seawater pH and subsequently combined these data with quantitative modeling techniques to develop a scenario for the mass extinction. Their results show that seawater pH remained relatively stable during the first phase of the extinction, but rapidly shifted to more acidic values during the second phase, which lasted ~ 10 thousand years. This acidification of the oceans had dramatic consequences for life on Earth and is thought to be associated with the release of massive amounts of carbon, related to the volcanism of the Siberian Traps. Up to 96 % of living marine species became extinct during the Permian-Triassic mass extinction and now, it has been shown for the first time that ocean acidification was the responsible mechanism.

Journal reference: Clarkson, M. O., Kasemann, S. A., Wood, R. A., Lenton, T. M., Daines, S. J., Richoz, S., … & Tipper, E. T. (2015). Ocean acidification and the Permo-Triassic mass extinction. Science348(6231), 229-232.

Image: Eruption of the Tavurvur volcano on February 13, 2009 near Rabaul, New Britain, Papua New Guinea. Source: Taro Taylor, Wikimedia Commons.

Species extinction rates higher than previously thought

According to a new study performed by biologists, the current extinction rates of terrestrial animal and plant species associated with human activities may be up to 10 times higher than previously thought. By using fossil datasets and mathematical models, the scientists were able to estimate new natural background rates of species diversification and extinction. Their results indicate that until now, these background rates are likely to have been overestimated and should be in the order of 0.1 extinction per million species per year, rather than 1 extinction per million species per year. Because current rates of extinction are compared against background levels, these new results have major implications for the apparent impact of mankind on life on Earth: the effects may be even more severe than expected.

Journal reference: De Vos, J. M., Joppa, L. N., Gittleman, J. L., Stephens, P. R., & Pimm, S. L. (2014). Estimating the normal background rate of species extinction. Conservation Biology.

Image: Fossil remains of Archaeopteryx displayed in the Museum für Naturkunde in Berlin, Germany. Source: H. Raab, Wikimedia Commons.