Measuring Global Trends in the Status of Biodiversity: Red List Indices for Birds

The rapid destruction of the planet's biodiversity has prompted the nations of the world to set a target of achieving a significant reduction in the rate of loss of biodiversity by 2010. However, we do not yet have an adequate way of monitoring progress towards achieving this target. Here we present a method for producing indices based on the IUCN Red List to chart the overall threat status (projected relative extinction risk) of all the world's bird species from 1988 to 2004. Red List Indices (RLIs) are based on the number of species in each Red List category, and on the number changing categories between assessments as a result of genuine improvement or deterioration in status. The RLI for all bird species shows that their overall threat status has continued to deteriorate since 1988. Disaggregated indices show that deteriorations have occurred worldwide and in all major ecosystems, but with particularly steep declines in the indices for Indo-Malayan birds (driven by intensifying deforestation of the Sundaic lowlands) and for albatrosses and petrels (driven by incidental mortality in commercial longline fisheries). RLIs complement indicators based on species population trends and habitat extent for quantifying global trends in the status of biodiversity. Their main weaknesses are that the resolution of status changes is fairly coarse and that delays may occur before some status changes are detected. Their greatest strength is that they are based on information from nearly all species in a taxonomic group worldwide, rather than a potentially biased subset. At present, suitable data are only available for birds, but indices for other taxonomic groups are in development, as is a sampled index based on a stratified sample from all major taxonomic groups.

全球生物多样性正快速丧失，促使世界各国制定了到2010年大幅降低生物多样性丧失速率的目标。然而，当前我们仍缺乏足够的方法来监测该目标的实现进展。为此，我们提出了一种基于世界自然保护联盟红色名录（IUCN Red List）构建指数的方法，用以绘制1988年至2004年间全球所有鸟类物种的整体受威胁状况（预测的相对灭绝风险）。红色名录指数（Red List Indices, RLIs）的构建依据是各红色名录等级中的物种数量，以及评估周期内因物种保护状况真正改善或恶化而发生等级变更的物种数量。全球所有鸟类的红色名录指数显示，自1988年以来，鸟类的整体受威胁状况持续恶化。细分后的指数显示，全球范围内及所有主要生态系统中的鸟类受威胁状况均出现恶化，其中印度-马来亚鸟类群（受巽他低地森林砍伐加剧驱动）以及信天翁与海燕类（受商业延绳钓渔业的误捕致死驱动）的指数降幅尤为显著。红色名录指数可与基于物种种群趋势及栖息地范围的指标互为补充，共同用于量化生物多样性状况的全球变化趋势。该指数的主要局限在于：物种受威胁状况变更的分辨率相对较粗，且部分状况变更可能存在检测滞后性。其最大优势在于，该指数基于全球某一分类群中几乎所有物种的相关数据，而非存在潜在偏差的子集样本。当前仅鸟类类群拥有适配的数据，但其他分类群的红色名录指数正处于研发阶段，同时基于所有主要分类群分层抽样的抽样指数也在开发之中。