Revisiting global trends in freshwater insect biodiversity: A reply

Jahnig et al. make some useful points regarding the conclusions that can be drawn from our meta-analysis; however, some issues require clarification. First, we never suggested that there was a globally increasing trend of freshwater insect abundances, but only spoke of an average increasing trend in the available data. We also did not suggest that freshwater quality has improved globally, but rather that documented improvements in water quality can explain at least some of the trends we observed. Second, as we acknowledged, our data are not a representative set of freshwater ecosystems around the world, but they are what is currently accessible. Third, there is indeed no doubt that changes in abundance or biomass need not correlate with changes in other aspects of biodiversity, such as species richness or functional composition. Our analysis was specifically focused on trends in community abundance/biomass because it has been the subject of recent study and speculation, and is a widely available metric in long-term studies. To better understand the recent changes in freshwater insect assemblages, we encourage freshwater ecologists to further open their troves of data from countless long-term monitoring schemes so that larger and more comprehensive syntheses can be undertaken. This article is categorized under: Water and Life > Conservation, Management, and Awareness

Automated summary

The authors address points raised by Jahnig et al., clarifying that they did not suggest a global increasing trend in freshwater insect abundances, but rather an average increasing trend in available data. They also did not imply global improvements in freshwater quality, but noted that documented improvements can explain some observed trends. They encourage freshwater ecologists to share more long-term monitoring data for larger and more comprehensive syntheses.