Collins James P, Halliday Tim
School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
Philos Trans R Soc Lond B Biol Sci. 2005 Feb 28;360(1454):309-14. doi: 10.1098/rstb.2004.1588.
Amphibian population declines and sudden species' extinctions began to be noted at the beginning of the 1980s. Understanding the causes of the losses is hampered by our poor knowledge of the amphibian fauna in many parts of the world. Amphibian taxa are still being described at a high rate, especially in the tropics, which means that even quantifying species lost as a percentage of the current fauna can be a misleading statistic in some parts of the globe. The number of species that have gone missing is only one measure of the loss of biodiversity. Long-term studies of single-species populations are needed, but this approach has its limits. Amphibian populations often show great annual variation in population size making it difficult, if not impossible, to use short-term studies as a basis for deciding if a population is increasing or decreasing in the long term. Aggregating single studies into databases and searching for patterns of variation is a way of overcoming this limitation. Several databases on species and population time series are available or in development. These records show that declines are continuing worldwide with some species and populations, especially in the tropics and at higher elevations, at greater risk of extinction than others. Unfortunately, amphibian databases with population time series have much less information for the tropics compared to the temperate zone, and less for Africa and Asia compared with Europe and North America. Focusing limited resources using comprehensive statistical designs is a way to maximize the efficiency and effectiveness of monitoring efforts. It is clear that, in the first decades of the twenty-first century, the regions of the globe with the highest diversity of amphibian species will experience the greatest rates of decrease of forests and increase in human population size, fertilizer use, agricultural production, creation of new croplands and irrigation. Many of these changes are likely negatively to affect amphibian species diversity, and their influence must be understood before concluding, at least for amphibians, that the 2010 millennium assessment goal of significantly reversing the rate of loss of Earth's biodiversity can be met.
20世纪80年代初，两栖动物数量开始减少，物种突然灭绝的现象也开始受到关注。由于我们对世界许多地区的两栖动物区系了解不足，因此很难理解这些损失的原因。两栖动物分类群仍在以很高的速度被描述，特别是在热带地区，这意味着在全球某些地区，即使将物种损失数量量化为当前动物区系的百分比，也可能是一个误导性的统计数据。物种消失的数量只是生物多样性丧失的一个衡量标准。需要对单物种种群进行长期研究，但这种方法也有其局限性。两栖动物种群数量通常每年都有很大变化，这使得即使不是不可能，也很难将短期研究作为判断一个种群长期内是增加还是减少的依据。将单个研究汇总到数据库中并寻找变化模式是克服这一局限性的一种方法。目前有几个关于物种和种群时间序列的数据库可供使用或正在开发中。这些记录表明，全球范围内两栖动物数量仍在持续下降，一些物种和种群，特别是在热带地区和高海拔地区，比其他物种和种群面临更大的灭绝风险。不幸的是，与温带地区相比，拥有种群时间序列的两栖动物数据库在热带地区的信息要少得多，与欧洲和北美相比，非洲和亚洲的信息也更少。利用全面的统计设计集中有限的资源是提高监测工作效率和效果的一种方法。很明显，在21世纪的头几十年里，两栖动物物种多样性最高的全球区域将经历森林减少和人口规模、化肥使用、农业生产、新农田开垦和灌溉增加速度最快的时期。这些变化中的许多可能会对两栖动物物种多样性产生负面影响，在得出至少对于两栖动物而言能够实现2010年千年评估中大幅扭转地球生物多样性丧失速度这一目标的结论之前，必须了解它们的影响。
