什么引起五次生物大灭绝?  

What caused the five mass extinctions?

作　　者：沈树忠[1] 张华[1] SHEN ShuZhong ZHANG Hua(State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China)

机构地区：[1]中国科学院南京地质古生物研究所现代古生物学和地层学国家重点实验室,南京210008

出　　处：《科学通报》2017年第11期1119-1135,共17页Chinese Science Bulletin

基　　金：国家自然科学基金(41290260);中国科学院战略性先导科技专项(B类)(XDB18000000)资助

摘　　要：尽管多数生物学家认为当今地球正处于一次前所未有的生物大灭绝之中,然而由于人类拥有的直接观察记录非常短暂,难于正确判断当今地球将来的发展趋势和潜在的危机.地质历史时期曾经发生了五次重大生物灭绝事件,这些事件造成当时海洋中至少75%的物种在短时间内灭绝,陆地生态系统形成以后,也同样遭到重创.这些生物大灭绝事件发生的原因成为评估当今地球生态系统危机的重要依据.根据对5亿多年以来发生的五次生物大灭绝(分别发生在奥陶纪末、泥盆纪晚期F/F、二叠纪末、三叠纪末和白垩纪末)生物的种类、灭绝模式以及环境背景分析表明,地球上显生宙以来还没有发生过造成整个地球生物圈彻底毁灭的灾变事件,地质历史时期发生的五次生物大灭绝均伴随有剧烈的环境变化,大气CO_2、温度(包括冰室效应和温室效应)、海洋酸化、海平面变化和海水缺氧等全球性的气候、环境剧变是造成生物大灭绝的主要原因.导致这种环境灾变最为常见的触发机制是超大规模的火山活动,火山活动不但喷出大量CO_2等温室气体,同时可以触发大量蕴藏在内陆盆地和大陆架上的甲烷气体等快速释放.地外体撞击、超新星爆发、太阳耀斑爆发等事件可能会瞬间毁灭地球,但并不是地质历史时期已经发生的生物大灭绝的主因.Although a majority of biologists are convinced that a mass extinction is underway on earth today, the human history with direct observatory data is too short to predict its future trends. At least five mass extinctions occurred during the Phanerozoic Eon, causing the rapid extinction of at least 75% of existing marine species; they also seriously affected species diversity on land once the terrestrial ecosystem developed. The causes and consequences of these mass extinctions have become the most useful analogs for understanding whether the current global ecosystem is experiencing an extinction event. Previous multidisciplinary studies of the extinction patterns of fossil groups and concurrent environmental changes of the five mass extinctions during the past 500 million years（occurring in the end-Ordovician, Late Devonian Frasnian-Famennian, end-Permian, end-Triassic, and end-Cretaceous） suggested that no catastrophic event wiped out all organisms on earth. However, all five mass extinctions were associated with serious environmental deterioration and major paleoclimatic changes. The end-Ordovician mass extinction, occurring 445.2–443.8 million years ago, consists of two phases separated by an interval dominated by the cold Hirnantia fauna. The wax and wane of glaciation and associated widespread anoxia were the major causes of the two phases of the end-Ordovician mass extinctions. The Late Devonian mass extinction consists of a few different events from the Givetian to the Devonian-Carboniferous boundary, of which the most important is the Kellwasser event around the Frasnian-Famennian boundary. This extinction most seriously affected the coral and stromatoporoid reefs, and caused the extinction of two brachiopod orders（Pentamerida and Atrypida）. As of yet, there is no consensus on the cause of this extinction event. Global cooling related to the widespread development of the terrestrial vegetation ecosystem and marine anoxia are the two most plausible scenarios. Although impact events were reported f

关 键 词：生物大灭绝 火山喷发 温室效应 冰室效应 环境恶化 

分 类 号：Q111.7[生物学—普通生物学]