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).