Impacts of experimental climate warming on wildflowers and pollinators in a cereal agro-ecosystem

Climate change poses a significant threat to pollinating insects and wildflowers. While many studies have documented changes in phenology and distributions for subsets of plants or pollinators, little is known about how entire communities of interacting species will be affected or what subsequent impacts there may be on pollination. We ran an open-air field experiment employing infra-red heaters to simulate climate-warming in arable farmland. We increased temperature by 1.5°C and rainwater by 40% for two growing seasons to investigate how climate change may impact wildflower floral resources, insect visitation, plant-pollinator interaction networks (by applying graph theory to food webs to describe community structure), and wildflower seed set. Experimental warming reduced total floral abundance, nectar volumes, and visitor abundance, though the latter effect was mediated by visitor community composition. Warming increased flower visits and the complexity of the plant-pollinator interaction networks. Seed set was reduced for several specialist wildflower species and increased for a generalist one. Precipitation had no effects. Our findings demonstrated a flow of negative impacts through the plant-pollinator community, which accumulated to affect community structure and ecosystem functioning. The results also highlighted several mechanisms that could drive changes in community composition over time.