Timing and causes of mid-Holocene mammoth extinction on St. Paul Island, Alaska
Timing and causes of mid-Holocene mammoth extinction on St. Paul Island, Alaska
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DOI：
10.1073/pnas.1604903113
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发表时间：
2016-08-16
影响因子：
11.1
通讯作者：
Wooller, Matthew J.
中科院分区：
文献类型：
--
作者：
Graham, Russell W.;Belmecheri, Soumaya;Wooller, Matthew J.
在大陆种群灭绝后，遗留的长毛猛犸（Mammuthus mammoth genius）种群在几个小的白令群岛上存活了数千年。在这里，我们提出多代理古环境记录调查的时间，原因和后果的猛犸从圣保罗岛，阿拉斯加消失。五个独立的灭绝指标表明，猛犸象生存在圣保罗，直到5,600 +/- 100年前。在灭绝窗口期，岛上的植被组成保持稳定，在1787年之前没有人类存在的证据，这表明这些因素不是灭绝的驱动因素。相反，从岛上一个淡水湖的沉积物岩芯中的沉积磁化率、氧同位素、硅藻和枝藻组合，以及猛犸遗骸中的稳定氮同位素可以推断出，在7,850年至5,600年前，生物灭绝与淡水资源的减少和气候干燥相吻合。与其他关于圣保罗猛犸种群的灭绝模型相反，这一证据表明，由于海平面上升和区域气候变化造成的岛屿面积缩小和淡水短缺的协同效应，这一猛犸种群灭绝了。湖周围猛犸活动加剧造成的水质退化可能加剧了这种情况。圣保罗猛犸的死亡现在是最好的史前遗迹之一，突出了淡水限制作为一个被忽视的灭绝驱动力，并强调了小岛屿人口对环境变化的脆弱性，即使在没有人类影响的情况下。
Relict woolly mammoth (Mammuthus primigenius) populations survived on several small Beringian islands for thousands of years after mainland populations went extinct. Here we present multiproxy paleoenvironmental records to investigate the timing, causes, and consequences of mammoth disappearance from St. Paul Island, Alaska. Five independent indicators of extinction show that mammoths survived on St. Paul until 5,600 +/- 100 y ago. Vegetation composition remained stable during the extinction window, and there is no evidence of human presence on the island before 1787 CE, suggesting that these factors were not extinction drivers. Instead, the extinction coincided with declining freshwater resources and drier climates between 7,850 and 5,600 y ago, as inferred from sedimentary magnetic susceptibility, oxygen isotopes, and diatom and cladoceran assemblages in a sediment core from a freshwater lake on the island, and stable nitrogen isotopes from mammoth remains. Contrary to other extinction models for the St. Paul mammoth population, this evidence indicates that this mammoth population died out because of the synergistic effects of shrinking island area and freshwater scarcity caused by rising sea levels and regional climate change. Degradation of water quality by intensified mammoth activity around the lake likely exacerbated the situation. The St. Paul mammoth demise is now one of the best-dated prehistoric extinctions, highlighting freshwater limitation as an overlooked extinction driver and underscoring the vulnerability of small island populations to environmental change, even in the absence of human influence.