The end-Permian biotic crisis
The end-Permian crisis, which occurred approximately 250 Million years ago, is long known for its impact on marine ecosystems. Megafossils of plants and animals show that the crisis dramatically affected the terrestrial realm as well. Elimination of species may have occurred stepwise over a prolonged period, and was punctuated by a final extinction pulse. There is still animated discussion on the cause of the end-Permian crisis. The proposed concepts differ with respect to source (extraterrestrial or terrestrial) and rate (catastrophic to relatively rapid). Several terrestrial-bound scenarios have been proposed to explain the end Permian crisis. These involve worldwide oceanographic and/or atmospheric perturbations, which also are associated with the present-day ecological crisis, such as increasing CO2 levels, ozone reduction, acid rain, climate changes, sea level changes and oceanic anoxia. A major candidate for causing the end-Permian crisis is the massive volcanic activity in Siberia. The eruption of large-volume flood basalts took place in a relatively short period of time that closely corresponds to the end-Permian extinction interval. In order to contribute to a botanical perspective of this crisis and its aftermath, megafossils as well as pollen grains and spores from Europe and Greenland were studied.