Alford R A, Dixon P M, Pechmann J H
School of Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia.
Nature. 2001 Aug 2;412(6846):499-500. doi: 10.1038/35087658.
The decline and disappearance of relatively undisturbed populations of amphibians in several high-altitude regions since the 1970s suggests that they may have suffered a global decline, perhaps with a common cause or causes. Houlahan et al. examined means of trends for 936 amphibian populations and concluded that global declines began in the late 1950s, peaked in the 1960s, and have continued at a reduced rate since. Here we re-analyse their data using a method that accounts for the sampling of different populations over different time periods, and find evidence of a mean global decline in monitored populations only in the 1990s. However it is calculated, the global mean not only masks substantial spatial and temporal variation in population trends and sampling effort, but also fails to distinguish between a global decline with global causes and the cumulative effects of local declines with local causes.
自20世纪70年代以来，几个高海拔地区相对未受干扰的两栖动物种群数量减少乃至消失，这表明它们可能在全球范围内数量下降，或许存在一个或多个共同原因。胡拉汉等人研究了936个两栖动物种群数量变化趋势的均值，得出结论称全球数量下降始于20世纪50年代末，在60年代达到峰值，此后下降速度有所减缓但仍在持续。在此，我们使用一种考虑了不同时间段不同种群抽样情况的方法重新分析了他们的数据，发现仅有监测种群在20世纪90年代出现全球数量均值下降的证据。无论如何计算，全球均值不仅掩盖了种群数量趋势和抽样工作在空间和时间上的巨大差异，还无法区分由全球原因导致的全球数量下降与由局部原因导致的局部数量下降的累积效应。
