Fig. 12

Forest plots showing maximum negative effects on Chironomidae abundance during the study period in each included study. The size of the squares is proportional to the weight of the studies, which is based on the number of replicates. Liber (1998) and Bordalo (2021) reported separate abundance data for different chironomid species, but to avoid statistical dependence we have used data for only one species. To obtain a conservative estimate of negative effects the species showing the least negative effect was selected (results do not change significantly if other species are used). Data represents eight regions (four in Europe, three in North America, one in Asia). Study labels refer to short reference and study name information as recorded in Additional file 6