A recent global meta‐analysis reported a decrease in terrestrial but increase in freshwater insect abundance and biomass (van Klink et al., Science 368, p. 417). The authors suggested that water quality has been improving, thereby challenging recent reports documenting drastic global declines in freshwater biodiversity. We raise two major concerns with the meta‐analysis and suggest that these account for the discrepancy with the declines reported elsewhere. First, total abundance and biomass alone are poor indicators of the status of freshwater insect assemblages, and the observed differences may well have been driven by the replacement of sensitive species with tolerant ones. Second, many of the datasets poorly represent global trends and reflect responses to local conditions or nonrandom site selection. We conclude that the results of the meta‐analysis should not be considered indicative of an overall improvement in the condition of freshwater ecosystems.

中文翻译：

---

重新审视全球淡水昆虫生物多样性趋势

最近的一项全球荟萃分析报告说，陆地上的昆虫减少了，但淡水昆虫的丰度和生物量却增加了（van Klink等，科学368，第417页）。作者认为水质一直在改善，因此对最近的报告表明全球淡水生物多样性急剧下降的报告提出了挑战。我们在荟萃分析中提出了两个主要问题，并建议这与其他地方报道的下降有差异。首先，总的丰度和生物量本身并不是淡水昆虫种群状况的较差指标，而且观察到的差异很可能是由敏感物种替换为耐性物种造成的。其次，许多数据集不能很好地反映全球趋势，无法反映对当地条件或非随机地点选择的反应。