大滅絕之前的預警

原文網址：https://www.fau.eu/2018/03/14/news/research/mass-extinction-with-prior-warning/

大滅絕之前的預警

跟過往推測的相反，大滅絕之前確實會有警訊出現

在地球歷史上曾發生過的大滅絕事件都有被確實記錄下來，科學家相信它們的發生歷程從地質角度來看不過是短短一下子。但在一篇新發表的研究中，愛爾朗根―紐倫堡大學的古生物學家和他們合作的研究人員顯示，地球歷史上最劇烈的大滅絕事件逐漸變得清晰的時間比過往認為的還要早了許多，並指出相同的跡象也可以在今日觀察到。

大滅絕這種罕見事件會導致嚴重的後果。它們通常會澈底改變演化的方向，舉例來說，如果6500萬年前恐龍沒有滅亡的話，那哺乳類大概也不可能崛起――連帶根絕了人類的出現。當時有顆小行星撞擊地球使得地球瞬間陷入黑暗之中，並讓氣溫大幅降低。超過70%的動物種類因為隨後產生的飢荒而滅亡，人類的祖先是幸運的倖存者之一。

2.5億年前發生在二疊紀―三疊紀交界的物種滅絕事件造成的後果還要更加慘烈。超大規模的火山爆發及排放出來的溫室氣體據估計消滅了將近90%的動物種類。超過20年來，學術圈的主流看法認為這起「災難之最」是在毫無預警的情況下突然發生，他們估計在地質年代表上此事件出現的時間只佔了6萬年而已。

在今日同樣能見到大滅絕的警訊

Wolfgang Kießling教授表示造成三疊紀末大滅絕的因素呼應了我們今日所見的許多現象。「有很多證據顯示出我們正面臨嚴重的全球暖化、海洋酸化與海洋缺氧。我們跟過往事件的差異在於這些現象的嚴重程度。舉例來說，今日的溫度上升幅度相較於2.5億年前還低了許多。」

然而，Wolfgang Kießling團隊發現導致二疊紀步入終結的警訊已經可以在今日看見。「我們現在觀察到各類棲地中，生物的滅絕速率都在提高，這可以直接歸因於人類造成的影響，像是破壞棲地、過度漁撈和汙染。特別是海洋動物的體型縮小十分明確地呈現了氣候變遷帶來的後果。我們應該要嚴加看待這些徵兆。」

此研究由設立於FAU的研究單位TERSANE執行(編號2332)。在此跨領域計畫中，8組研究團隊探討自然排放的溫室氣體在什麼情況下會升高至具有致災能力，以及溫室氣體和生物多樣性危機的關聯為何。

Mass extinction with prior warning

Warning signs for mass extinction do exist, contrary to previous assumptions

Mass extinctions throughout the history of the Earth have been well documented. Scientists believe that they occurred during a short period of time in geological terms. In a new study, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) palaeobiologists and their research partners have now shown that signs that the largest mass extinction event in the Earth’s history was approaching became apparent much earlier than previously believed, and point out that the same indicators can be observed today.

Mass extinctions are rare events that have catastrophic consequences. These events often completely change the course of evolution. For example, the rise of mammals – and therefore of humans – would probably not have been possible had dinosaurs not become extinct 65 million years ago. A meteorite hit the Earth plunging it into darkness and causing a huge drop in temperature. The subsequent hunger crisis wiped out more than 70 percent of all animal species. Man’s ancestors were among the lucky survivors.

The consequences of the extinction of species that occurred around 250 million years ago at the Permian-Triassic boundary were even more catastrophic. Gigantic volcanic eruptions and the greenhouse gas emissions they caused wiped out around 90 percent of all animal species according to estimates. For over twenty years, the dominant opinion in research was that this ‘mother of all disasters’ happened abruptly and without warning, when seen on a geological time-scale – estimates suggest a period of just 60,000 years.

In a new study published in the March edition of the renowned magazine ‘Geology’, a team of researchers from Germany and Iran have proved that this crisis happened over a longer period of time. Under the leadership of Prof. Dr. Wolfgang Kießling, Chair for Palaeoenviromental Research at FAU, who has also recently been appointed as lead author for the sixth World Climate Report, and Dr. Dieter Korn from the Museum für Naturkunde in Berlin, the scientists examined fossils in largely unresearched geological profiles in Iran . Their results show that the first indicators of a mass extinction were evident as early as 700,000 years prior to the actual event. Several species of ammonoids were killed off at that time and the surviving species became increasingly smaller in size and less complex the closer the main event became.

發表在知名期刊《地質》(Geology)三月號的一篇新研究中，德國和伊朗的研究團隊證明這起危機的持續時間還要更久。領導該團隊的為FAU古環境學研究中心的主任教授Wolfgang Kießling博士，他最近也被任命為第六次全球氣候報告的主要作者；另一位則是柏林自然博物館的Dieter Korn博士。這群科學家仔細檢驗了從伊朗一處大部分未被研究的地質剖面中挖出的化石，結果顯示早在事件實際發生的70萬年以前，大滅絕的第一筆跡象就已經清晰可見。當時有幾種菊石已經消失，而剩下來的種類越接近主要事件的發生時間，體型也變得越來越小。

The warning signs of mass extinction are also visible today

The factors that led to a mass extinction at the end of the Permian Period remind us very much of today, says Prof. Wolfgang Kießling. ‘There is much evidence of severe global warming, ocean acidification and a lack of oxygen. What separates us from the events of the past is the extent of these phenomena. For example, today’s increase in temperature is significantly lower than 250 million years ago’.

However, the warning signs that Wolfgang Kießling’s team found towards the end of the Permian Period can already be seen today. ‘The increased rate of extinction in all habitats we are currently observing is attributable to the direct influence of humans, such as destruction of habitat, over-fishing and pollution. However, the dwarfing of animal species in the oceans in particular can be quite clearly attributed to climate change. We should take these signs very seriously.’

The work was carried out by the TERSANE research unit, which is based at FAU (FOR 2332). In this interdisciplinary project, eight working groups investigated under which conditions natural greenhouse gas emissions can reach catastrophic levels and how they are connected to crises in biodiversity.

原始論文：Wolfgang Kiessling, Martin Schobben, Abbas Ghaderi, Vachik Hairapetian, Lucyna Leda, Dieter Korn. Pre–mass extinction decline of latest Permian ammonoids. Geology, 2018; 46 (3): 283 DOI: 10.1130/G39866.1

引用自：University of Erlangen-Nuremberg. "Mass extinction with prior warning: Warning signs for mass extinction do exist, contrary to previous assumptions."