Direct and indirect effects of ILUC on ecosystem functioning
The SEM indicated a consistent negative effect of ILUC on standing fish biomass (Table S10). Overall (including Amazon and Uruguay streams) the total effect of ILUC on standing fish biomass was composed of a direct negative path from ILUC (–0.126; Figure 6a,b) and indirect paths. The indirect paths were mediated by negative effects on fish and macrophyte taxonomic richness (Figure 6c; SEM: fish richness: –0.063, macrophyte richness: –0.110) and fish functional diversity (Figure 6d; SEM: fish functional diversity: –0.150). Therefore, indirect effects of ILUC on ecosystem functioning were as strong as direct effects. Notably, there were strong positive links among the three assemblages – manifested through positive effects of macrophytes on arthropod and fish taxonomic richness and functional diversity (Figure 6). Similarly, arthropod taxonomic richness and functional diversity positively affected fish taxonomic richness and functional diversity (Figure 6). Comparing the results of SEM between the two study regions (Amazonas and Uruguay separately), we observed stronger links among taxonomic richness and functional diversity of fish, arthropod, and macrophyte in Amazonia than in Uruguay streams (Figure S5, Tables S8 and S9).