How does elevated carbon dioxide (CO₂) affect plant–herbivore interactions? A field experiment and meta-analysis of CO₂-mediated changes on plant chemistry and herbivore performance

Abstract

First, we report the results of the longest-known field study (9 years) to examine the effects of elevated carbon dioxide (CO₂) on leaf miner densities in a scrub-oak community at Kennedy Space Center, Florida. Here, the densities of all leaf miner species (6) on all host species (3) were lower in every year in elevated CO₂ than they were in ambient CO₂. Second, meta-analyses were used to review the effects of elevated CO₂ on both plants (n=59 studies) and herbivores (n=75 studies). The log of the response ratio was chosen as the metric to calculate effect sizes. Results showed that elevated CO₂ significantly decreased herbivore abundance (−21.6%), increased relative consumption rates (+16.5%), development time (+3.87%) and total consumption (+9.2%), and significantly decreased relative growth rate (−8.3%), conversion efficiency (−19.9%) and pupal weight (−5.03%). No significant differences were observed among herbivore guilds. Host plants growing under enriched CO₂ environments exhibited significantly larger biomass (+38.4%), increased C/N ratio (+26.57%), and decreased nitrogen concentration (−16.4%), as well as increased concentrations of tannins (+29.9%) and other phenolics. Effects of changes on plant primary and secondary chemistry due to elevated CO₂ and consequences for herbivore growth and development are discussed.