Jähnig, Sonja C.; Baranov, Viktor; Altermatt, Florian; Cranston, Peter; Friedrichs-Manthey, Martin; Geist, Juergen; He, Fengzhi; Heino, Jani; Hering, Daniel; Hölker, Franz; Jourdan, Jonas; Kalinkat, Gregor; Kiesel, Jens; Leese, Florian; Maasri, Alain; Monaghan, Michael T.; Schäfer, Ralf B.; Tockner, Klement; Tonkin, Jonathan D.; Domisch, Sami
(Wiley, 2020)
WIREs Water 8 (2020)
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 tolocal conditions or nonrandom site selection. We conclude that the results of the meta-analysis should not be considered indicative of an overall improve ment in the condition of freshwater ecosystems.