City hives a risk to bees

Francis Ratnieks and Karin Alton at the University of Sussex’s Laboratory of Apiculture and Social Insects (LASI) report in the journal The Biologist that urban beekeeping has never been more popular, particularly in London, but the boom could be bad for honey bees and other flower-visiting insects as it risks overtaxing the available nectar and pollen supply, and potentially encourages the spread of diseases.

Data from BeeBase, a register of apiaries maintained by the UK’s National Bee Unit (NBU), shows that in five years, from 2008-13, the number of beekeepers in Greater London tripled from 464 to 1,237, and the number of hives doubled from 1,677 to more than 3,500.

Ratnieks and Alton says the beekeeping boom has seen London reach about 10 hives per square kilometre, compared to about one per square kilometre in England as a whole.

Many restaurants, galleries, businesses and shops use rooftop hives as a means of visibly greening their business or as a team-building exercise for staff.

“Both honey bees and wild bees have been declining,” Ratnieks says. “Although the causes are complex the most important one seems to be loss of flowers and habitat…. If the problem is not enough flowers, increasing the number of hives risks making that problem worse… If a game park was short of food for elephants, you wouldn’t introduce more elephants, so why should we take this approach with bees?”

High colony density in London and an influx of inexperienced beekeepers also runs the risk of spreading certain honey bee diseases, especially American foulbrood (AFB), now rare in Britain. The “cure” for AFB, a highly contagious bacterial infection of honey bee larvae, is to burn the hive because it has very long-lived spores that contaminate the wax combs.

The scientists calculate each new hive in London would need the equivalent of 1ha of borage, a plant that attracts mainly honey bees, or 8.3ha of lavender, a plant that attracts mainly bumblebees but some honey bees, to support it.

Honey bee numbers may have declined but the species is in no imminent danger of extinction, unlike some other critically endangered insects in the UK, they add.