The Late Permian crisis: the continental record from Russia.

二叠纪末的危机标志着已知最大的生命大灭绝。大约50%的植物和动物在海洋中灭绝，相当于80-96%的物种消失。这场危机对陆地上的生物可能同样糟糕，但它们还没有得到解决。这一事件在局部范围内似乎同样严重：对中国岩石演替的密切研究表明，超过90%的物种灭绝。但这一事件持续了多久？它是一夜之间发生的，还是经历了数千年甚至数百万年？观点已经改变：10年前，人们认为它已经持续了1000万年（Myr），但新的测年方法表明它可能持续了50万年或更少。2这些日期仍然有争议。是一个事件还是两个？曾经被认为是贯穿晚二叠世的一个漫长的灭绝阶段，现在被认为是两个事件，一个发生在大约2.6亿年前的Capitanian-Wuchiapingian边界（CW事件），另一个发生在2.51亿年前的二叠纪末事件，刚好低于二叠纪-三叠纪边界（PTB）。是什么导致了这场巨大的灾难？人们提出了许多观点，但现在有两个主要的假设，西伯利亚火山作用和影响。一些人热情地接受了影响的证据，但两份报告中的细节受到了严厉的批评。最广泛接受的PTB灭绝模型是一系列事件，这些事件发生在西伯利亚陷阱玄武岩的重复喷发之后，时间可能超过50万年。火山喷发将各种气体排入大气，导致严重的酸雨。酸雨杀死了陆地植物，土壤被剥离，破坏了陆地上的栖息地。二氧化碳的增加和全球变暖由于深海冻结储备中甲烷的大量释放而变得更糟，这两者结合起来产生了失控的温室效应，温度不断上升。全球变暖也导致海洋中的低氧条件。这杀死了90%或更多的海洋和陆地生物。早期的CW事件也有类似的模式，可能与中国的峨眉山火山有关。从大灭绝中恢复过来需要时间。在世界范围内，物种数量在早三叠世（大约600万年）仍然很低。然而，恢复期比这更长，正如各种“间隙”所表明的那样-主要生命模式的消失，例如珊瑚礁和森林（“煤间隙”）通过早三叠纪和中三叠纪，时间跨度为15-20百万年。到中三叠世末，俄罗斯各继承地的陆地生态系统还没有达到灭绝前的多样性，直到PTB事件后大约2500万~ 3000万年，群落才明显恢复到灭绝前的多样性和复杂性。理解PTB危机很重要，因为气候危机模型的许多特征今天正在重复：气体和酸雨的释放，数百年来的全球变暖，停滞的沃茨和物种的稳定损失。回顾过去可能是预测未来可能发生的事情的有用方法。我们可以在俄罗斯的几十个地方访问跨越CW和PTB边界的奇妙岩石部分。我们的英国和俄罗斯科学家团队希望解决一系列问题：陆地上物种灭绝的时间和模式如何与海洋中的物种灭绝相匹配？CW和P18事件在陆地上可以区分吗？从岩石上读到的环境变化是什么？有什么证据支持和反对在三叠纪开始时大规模的植物死亡和土壤冲刷？陆地上的生命是如何应对这两次危机的？生态系统崩溃的模式是什么？是否有生态或分类选择性的证据？全球陆地上的生命损失率是多少，与海洋危机的规模相比如何？在重建总体多样性和生态系统方面，早三叠世和中三叠世的恢复是什么性质的？

The end-Permian crisis marks the largest known mass extinction of life. About 50% of families of plants and animals died out in the sea, which scales to a loss of some 80-96% of species. The crisis was probably just as bad for organisms on land, but they have not been worked out yet. The event seems to have been just as serious at the local scale: close study of the rock succession in China shows that more than 90% of species died out. But how long did the event last? Was it a single, overnight hit, or did it take thousands, or even millions, of years? Opinions have changed: ten years ago, it was supposed to have lasted for 10 million years (Myr), but new dating methods show it lasted perhaps 0.5 Myr or less. These dates are still debated. Was it one event or two? What was once seen as a single long drawn-out extinction phase through the Late Permian is now seen as two events, one at the Capitanian-Wuchiapingian boundary (the CW event), some 260 Myr ago, and the end-Permian event, just below the Permo-Triassic boundary (PTB), 251 Myr ago. What caused this huge catastrophe? Many ideas have been suggested, but there are now two main hypotheses, Siberian volcanism and impact. Evidence for impact has been received enthusiastically by some, but the detail in both reports has been heavily criticised. The most widely accepted model for the PTB extinction is a chain of events following repeated eruptions of the Siberian Trap basalts over perhaps 0.5 Myr. The eruptions pumped a variety of gases into the atmosphere that led to severe acid rain. The acid rain killed land plants, and soil was stripped, destroying habitats on land. The rise in carbon dioxide and global warming was made worse by the dramatic release of methane from frozen reserves in the deep sea, which combined to give a runaway greenhouse effect, where temperatures just kept rising. Global warming also led to low oxygen conditions in the seas. This then killed 90% or more of life in the sea and on land. A similar pattern has been suggested for the earlier CW event, perhaps linked to the Emeishan volcanics in China. Recovery from the mass extinction took time. Worldwide, species numbers remained low through the Early Triassic, a time of perhaps 6 Myr. The recovery period was longer than that though, as indicated by various 'gaps' - disappearances of major life modes, such as coral reefs and forests (the 'coal gap') through the Early and Mid Triassic, a time span of 15-20 Myr. Ecosystems on land in the Russian successions had not achieved their pre-extinction diversities by the end of the Mid Triassic, and it was only some 25-30 Myr after the PTB event that communities apparently recovered their pre-extinction diversity and complexity. It's important to understand the PTB crisis since many features of the climate crisis model are being repeated today: release of gases and acid rain, global warming over hundreds of years, stagnant waters, and steady loss of species. Looking to the past may be a useful way to predict what may happen in the future. We have access to fantastic rock sections in Russia that cross the CW and PTB boundaries in dozens of places. With our team of British and Russian scientists, we want to tackle a whole string of questions: How do timings and patterns of extinction on land match those in the sea? Can the CW and P18 events be distinguished on land? What were the environmental changes, as read from the rocks? What evidence is there for and against the proposed massive plant killing and soil wash-off at the beginning of the Triassic? How did life on land respond to the two crises? What was the pattern of ecosystem collapse? Is there evidence for ecological or taxonomic selectivity? What were the global rates for loss of life on land, and how do these compare with the scale of the marine crisis? What was the nature of the recovery through the Early and Middle Triassic, in terms of rebuilding total diversity and ecosystems?