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Estimating the normal background rate of species extinction

机译：估计物种灭绝的正常本底率

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A key measure of humanity's global impact is by how much it has increased species extinction rates. Familiar statements are that these are 100-1000 times pre-human or background extinction levels. Estimating recent rates is straightforward, but establishing a background rate for comparison is not. Previous researchers chose an approximate benchmark of 1 extinction per million species per year (E/MSY). We explored disparate lines of evidence that suggest a substantially lower estimate. Fossil data yield direct estimates of extinction rates, but they are temporally coarse, mostly limited to marine hard-bodied taxa, and generally involve genera not species. Based on these data, typical background loss is 0.01 genera per million genera per year. Molecular phylogenies are available for more taxa and ecosystems, but it is debated whether they can be used to estimate separately speciation and extinction rates. We selected data to address known concerns and used them to determine median extinction estimates from statistical distributions of probable values for terrestrial plants and animals. We then created simulations to explore effects of violating model assumptions. Finally, we compiled estimates of diversificationthe difference between speciation and extinction rates for different taxa. Median estimates of extinction rates ranged from 0.023 to 0.135 E/MSY. Simulation results suggested over- and under-estimation of extinction from individual phylogenies partially canceled each other out when large sets of phylogenies were analyzed. There was no evidence for recent and widespread pre-human overall declines in diversity. This implies that average extinction rates are less than average diversification rates. Median diversification rates were 0.05-0.2 new species per million species per year. On the basis of these results, we concluded that typical rates of background extinction may be closer to 0.1 E/MSY. Thus, current extinction rates are 1,000 times higher than natural background rates of extinction and future rates are likely to be 10,000 times higher.
机译：衡量人类对全球影响的一项关键指标是人类增加了多少物种灭绝速度。熟悉的说法是，它们是人类灭绝前或背景灭绝水平的100-1000倍。估算最近的比率很简单，但是要建立一个比较的背景比率却不是。以前的研究人员选择的近似基准是每年每百万物种中有一种灭绝（E / MSY）。我们探索了不同的证据线，这些证据表明估计值要低得多。化石数据可直接估算出灭绝速率，但它们在时间上较为粗糙，主要限于海洋硬生物类群，通常不包括属。根据这些数据，典型的背景损失为每年每百万属0.01个属。分子系统发育可用于更多的分类单元和生态系统，但是人们争论是否可以将它们用于分别估计物种形成和灭绝速率。我们选择了数据来解决已知的问题，并使用它们从陆地动植物的可能值的统计分布中确定灭绝的中值。然后，我们创建了仿真来探索违反模型假设的影响。最后，我们编制了多样化的估计，即不同分类单元的物种形成率和灭绝率之间的差异。灭绝速率的中值估计范围为0.023至0.135 E / MSY。模拟结果表明，在分析大量系统发育史时，个别系统发育史的灭绝高估和低估部分相互抵消了。没有证据表明人类最近和广泛的总体多样性下降。这意味着平均灭绝率小于平均多样化率。中位数多样化率是每年每百万物种0.05-0.2个新物种。根据这些结果，我们得出结论，典型的背景消光率可能接近0.1 E / MSY。因此，目前的灭绝率是自然灭绝率的1,000倍，未来的灭绝率可能会高出10,000倍。

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