Florian Altermatt, Alain Maasri, Jens Kiesel, Martin Friedrichs-Manthey, Sonja C. Jähnig, Viktor Baranov, Ralf B. Schäfer, Juergen Geist, Klement Tockner, Michael T. Monaghan, Peter S. Cranston, Jonas Jourdan, Franz Hölker, Sami Domisch, Jani Heino, Gregor Kalinkat, Daniel Hering, Fengzhi He, Jonathan D. Tonkin, Florian Leese, University of Zurich, Jähnig, Sonja C, Baranov, Viktor, 3 Department of Biology II LMU Munich Biocenter Martinsried Germany, Altermatt, Florian, 4 Department of Evolutionary Biology and Environmental Studies University of Zurich Zürich Switzerland, Cranston, Peter, 6 Australian National University Canberra Australian Capital Territory Australia, Friedrichs‐Manthey, Martin, 1 Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) Berlin Germany, Geist, Juergen, 8 Aquatic Systems Biology Technical University of Munich, TUM School of Life Sciences Freising Germany, He, Fengzhi, Heino, Jani, 9 Freshwater Centre Finnish Environment Institute Oulu Finland, Hering, Daniel, 10 Aquatic Ecology University of Duisburg‐Essen Essen Germany, Hölker, Franz, Jourdan, Jonas, 11 Department of Aquatic Ecotoxicology Institute for Ecology, Evolution and Diversity, Goethe University Frankfurt am Main Frankfurt am Main Germany, Kalinkat, Gregor, Kiesel, Jens, Leese, Florian, 12 Aquatic Ecosystem Research University of Duisburg‐Essen Essen Germany, Maasri, Alain, Monaghan, Michael T., Schäfer, Ralf B., 13 Institute for Environmental Sciences, Quantitative Landscape Ecology University of Koblenz‐Landau Landau Germany, Tockner, Klement, Tonkin, Jonathan D., 15 School of Biological Sciences University of Canterbury Christchurch New Zealand, and Domisch, Sami
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. This article is categorized under: Water and Life > Conservation, Management, and Awareness, Relying on abundance or biomass and examining nonrepresentative datasets limits our ability to infer the condition of freshwater insect communities globally. Photo by Jeremy Monroe, Freshwaters Illustrated: a caddisfly larva from an Oregon Coastal stream, USA (Limnephilidae: Dicosmoecus sp.)., Federal Agency for Nature Conservation (BfN) http://dx.doi.org/10.13039/100010606, NSF Macrosystems Biology Program, Leibniz‐Gemeinschaft http://dx.doi.org/10.13039/501100001664