Additive Effects of Multiple Global Change Factors on Plant Invasions Are Common

Quantifying how co-acting global change factors (GCFs) influence plant invasion is crucial for predicting future invasion dynamics. We did a meta-analysis to assess pairwise effects of five GCFs (elevated CO₂, drought, eutrophication, increased rainfall and warming) on native and alien plants. We found that alien plants, compared to native plants, suffered less or benefited more for four of the eight pairwise GCF combinations, and that all GCFs acted additively. Subgroup analysis showed that the relative benefits of alien over native plants were particularly apparent when they grew in competition with one another, and that the results were largely the same when the aliens were restricted to naturalised or invasive species. Our meta-analysis provides evidence that additive effects of multiple global change factors on plant invasions are common, and thus that with the ongoing global environmental changes, the risk of plant invasion continues to increase.