The effects of human population density on trophic interactions are contingent upon latitude

Aim:  Studies conducted at a global scale are necessary to make general conclusions on the effect of urbanization on trophic interactions and explore how these effects change along latitudinal gradients. Since biotic interactions are more intense at lower latitudes, we predict they are less likely to be affected by human impacts than at higher latitudes. Therefore, we test the hypothesis that the effect of urbanization (quantified by human population density) on trophic interactions, specifically insect herbivory and bird predation, decreases with an increase in latitude
Location:  Global (881 study sties)
Time period: 2000-2021
Major taxa studied:  Birds, arthropods and plants.
Methods:  We compiled global data on insect herbivory and bird predation from individual studies using similar methodologies, and fitted generalized linear mixed models to test the effect of human population density, latitude and their interaction on these two response variables.
Results:  The intensity of herbi...