Elevated CO₂ Impacts on Plant-Pollinator Interactions: A Systematic Review and Free Air Carbon Enrichment Field Study

The impact of elevated CO₂ (eCO₂) on plant-pollinator interactions is poorly understood. This study provides the first systematic review of this topic and identifies important knowledge gaps. In addition, we present field data assessing the impact of eCO₂ (150 ppm above ambient) on bluebell (Hyacinthoides non-scripta)-pollinator interactions within a mature, deciduous woodland system. Since 1956, only 71 primary papers have investigated eCO₂ effects on flowering time, floral traits and pollination, with a mere 3 studies measuring the impact on pollination interactions. Our field experiment documented flowering phenology, flower visitation and seed production, as well as the abundance and phenology of dominant insect pollinators. We show that first and mid-point flowering occurred 6 days earlier under eCO₂, but with no change in flowering duration. Syrphid flies and bumble bees were the dominant flower visitors, with peak activity recorded during mid- and late-flowering periods. Whilst no significant difference was recorded in total visitation or seed set between eCO₂ and ambient treatments, there were clear patterns of earlier flowering under eCO₂ accompanied by lower pollinator activity during this period. This has implications for potential loss of synchrony in pollination systems under future climate scenarios, with associated long-term impacts on abundance and diversity.