A meta-analytical review of the effects of elevated CO2 on plant-anthropod interactions highlights the importance of interacting environmental and biological variables

An extensive meta-analysis of plant and animal responses to elevated CO2 was conducted. Over 5000 data points were extracted from 270 papers published between 1979 and 2009. These metadata were extracted from an exhaustive review and collection of relevant literature and attempted to synthesize and examine generalizations about herbivore response to CO2 across the literature. This study addressed the responses of insect herbivores to elevated carbon dioxide (CO2) across numerous insect orders and feeding guilds. The changes in 19 animal response variables to the main effect of elevated CO2 was examined. The study also addressed underlying plant mechanisms by quantifying those plant growth and metabolite responses most relevant to insect herbivory and examined how such responses were altered by numerous biotic and abiotic factors. Examined were the main effects of elevated CO2 on: six plant growth and allocation responses, seven primary metabolite responses, eight secondary metabolite responses, and four physical defense responses. These response variable changes were examined under two-way and three-way interactions between CO2 and: soil nitrogen, ambient temperature, drought, light availability, photosynthetic pathway, reproductive system, plant growth rate, plant growth form, tissue type, and nitrogen fixation.