Bees are at risk from climate change because more frequent droughts could cause plants to produce fewer flowers, researchers say.
A study by the University of Exeter examined the impact of droughts – which are expected to become more common in many parts of the world – on flowering plants.
Drought roughly halved the overall number of flowers, meaning less food for bees and other pollinators, it found.
The research, carried out in collaboration with the University of Manchester and the Centre for Ecology and Hydrology, is published in the journal Global Change Biology.
Ben Phillips, of the Environment and Sustainability Institute on the University of Exeter’s Penryn Campus in Cornwall, was joint lead researcher for the work.
“The plants we examined responded to drought in various ways, from producing fewer flowers to producing flowers that contained no nectar,” he said.
“But overall there was a very clear reduction in the number of flowers that were available – and obviously this means less food for flower-visiting insects such as bees.”
Bees are already under pressure from threats including including habitat loss, the use of particular pesticides and the spread of diseases.
Dr Ros Shaw, of the University of Exeter, said: “Not only are these insects vital as pollinators of crops and wild plants, but they also provide food for many birds and mammals.”
The study took place in Wiltshire on chalk grassland, an important habitat for UK pollinator species.
Plant species studied included meadow vetchling (Lathyrus pratensis), common sainfoin (Onobrychis viciifolia) and selfheal (Prunella vulgaris).
Dr Ellen Fry, from the University of Manchester, said: “Previous studies of the impacts of drought on flowers and bees have looked at individual species, often in the laboratory, but we used an experiment with rain shelters to examine the effects on real communities of plant species living in chalk grassland.
“The level of drought that we looked at was calculated to be a rare event, but with climate change such droughts are expected to become much more common.”
Results of the study suggest that chalk grasslands may support lower pollinator populations in the future.
However, the scientists warned the findings are likely to be broadly applicable to other regions and habitats.
The research was part of the Wessex Biodiversity and Ecosystem Service Sustainability project, and was funded by the Natural Environment Research Council.