Species-area relationships always overestimate extinction rates from habitat loss
Species-area relationships always overestimate extinction rates from habitat loss
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DOI：
10.1038/nature09985
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发表时间：
2011-05-19
期刊：
影响因子：
64.8
通讯作者：
Hubbell, Stephen P.
中科院分区：
文献类型：
--
作者：
He, Fangliang;Hubbell, Stephen P.
栖息地丧失导致的物种灭绝是21世纪的标志性保护问题(1)。尽管它很重要，但估计灭绝率仍然高度不确定，因为没有经过验证的直接方法或可靠数据来核实灭绝。最广泛使用的间接方法是通过反转物种-面积积累曲线来估计灭绝率，向后外推到较小的区域来计算预期的物种损失。基于这种方法估计的灭绝率几乎总是比实际观测到的高得多（2-5）。这种差异产生了“灭绝债务”的概念，指的是由于栖息地丧失和种群规模减少而在非平衡时期尚未灭绝的物种（6,7）。本文表明，目前定义的灭绝债务在很大程度上是一个采样人工产物，因为在构建物种-区域关系（SAR）和从栖息地丧失推断物种灭绝时，潜在的采样问题之间存在未被认识到的差异。关键的数学结果是，无论物种分布和空间尺度如何，清除一个物种的最后一个个体（灭绝）所需的面积，几乎总是比遇到一个物种的第一个个体所需的样本面积大得多。我们用来自美国大陆的大型森林地图和雀形目鸟类物种范围的全球网络数据来说明这些结果；我们发现高估可以超过160%。尽管我们得出结论，栖息地丧失导致的物种灭绝比以前认为的要严重，但我们的结果绝不能导致人们对栖息地丧失导致的物种灭绝感到自满，这是一个真实的、日益严重的威胁。
Extinction from habitat loss is the signature conservation problem of the twenty-first century(1). Despite its importance, estimating extinction rates is still highly uncertain because no proven direct methods or reliable data exist for verifying extinctions. The most widely used indirect method is to estimate extinction rates by reversing the species-area accumulation curve, extrapolating backwards to smaller areas to calculate expected species loss. Estimates of extinction rates based on this method are almost always much higher than those actually observed(2-5). This discrepancy gave rise to the concept of an 'extinction debt', referring to species 'committed to extinction' owing to habitat loss and reduced population size but not yet extinct during a non-equilibrium period(6,7). Here we show that the extinction debt as currently defined is largely a sampling artefact due to an unrecognized difference between the underlying sampling problems when constructing a species-area relationship (SAR) and when extrapolating species extinction from habitat loss. The key mathematical result is that the area required to remove the last individual of a species (extinction) is larger, almost always much larger, than the sample area needed to encounter the first individual of a species, irrespective of species distribution and spatial scale. We illustrate these results with data from a global network of large, mapped forest plots and ranges of passerine bird species in the continental USA; and we show that overestimation can be greater than 160%. Although we conclude that extinctions caused by habitat loss require greater loss of habitat than previously thought, our results must not lead to complacency about extinction due to habitat loss, which is a real and growing threat.