How urban heat affects bee populations

February 22, 2018 by Steve Frank, North Carolina State University
Credit: Elsa Youngsteadt

North Carolina is home to 500 species of wild bees, yet only a subset of these are common in cities and suburbs. People encourage wild bees by planting flowers and creating pollinator gardens to provide the pollen and nectar bees need. However, even gardens rich with flowers do not have the same bee abundance or diversity as natural areas. So, there must be things besides flowers that limit urban bee communities. But what are they?

In a recent paper, we show that one of these factors is the urban . The effect is caused by impervious surfaces – like cement and pavement – that absorb from the sun, making cities hotter than surrounding rural areas. We sampled bees for two years in 18 yards and parks around Raleigh, NC. These yards differed in flower abundance and diversity, but also differed in temperature. The hottest yards had about a third as many bees as yards just 2°C (about 3.6°F) cooler.

In addition, hot yards had fewer bees from species that we previously found to be sensitive to heat and more bees from species we found to be heat tolerant. We know from previous research that high temperatures can reduce bee survival by making them more susceptible to pathogens or less able to forage.

Yards with lots of flowers still had more bees and more kinds of bees than yards with few flowers but this was mitigated by yard temperature.

In other words, simply adding flowers to otherwise hot sites with lots of impervious surface cover is unlikely to restore pollinator communities. To amplify the benefits provided by , you could plant trees to shade driveways and sidewalks, reducing the temperature of a yard. We wouldn't expect other animals to thrive in poor habitats just by providing them with food. Bee conservation requires habitat restoration.

(This is a guest post by Steve Frank, an associate professor of entomology at NC State University.)

Explore further: Sick bees eat healthier

More information: April L. Hamblin et al. Wild bee abundance declines with urban warming, regardless of floral density, Urban Ecosystems (2018). DOI: 10.1007/s11252-018-0731-4

Elsa Youngsteadt et al. Urbanization Increases Pathogen Pressure on Feral and Managed Honey Bees, PLOS ONE (2015). DOI: 10.1371/journal.pone.0142031

Related Stories

Sick bees eat healthier

February 7, 2018

Dr Lori Lach, Senior Lecturer at JCU, said the study compared the feeding habits of healthy bees to those infected with the gut parasite Nosema ceranae.

Bees use invisible heat patterns to choose flowers

December 19, 2017

A new study, led by scientists from the University of Bristol, has found that a wide range of flowers produce not just signals that we can see and smell, but also ones that are invisible such as heat.

Bumble bees make a beeline for larger flowers

June 29, 2017

Bumble bees create foraging routes by using their experience to select nectar-rich, high-rewarding flowers. A study by Shohei Tsujimoto and Hiroshi Ishii of the University of Toyama in Japan now suggests that bees actually ...

Recommended for you

Looking beyond genes to explain blood cells' fates

March 19, 2018

Scientists often talk about cell fate and commitment in terms of mechanisms that control gene expression (transcription factors, chromatin remodeling, etc.). But by studying Diamond-Blackfan anemia (DBA), rare genetic blood ...

Drawing inspiration from plants and animals to restore tissue

March 19, 2018

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering have developed new wound dressings that dramatically accelerate healing ...

Researchers measure gene activity in single cells

March 16, 2018

For biologists, a single cell is a world of its own: It can form a harmonious part of a tissue, or go rogue and take on a diseased state, like cancer. But biologists have long struggled to identify and track the many different ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.