Why bees aren’t having sex in the heat

Bees Copyright Pixabay
By Marthe de Ferrer
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This World Bee Day we look at how bee bonking is being used to understand the climate crisis.


Today is World Bee Day, and after the positive news this week that a presumed-extinct species has been rediscovered, it turns out there are now different issues for the insect to contend with.

New research has found that bees struggle to reproduce in the heat. Rising temperatures are now believed to be partially sterilising insect populations. This unexpected side effect of global warming is bad news for us humans too, as bees pollinate a third of the food we eat.

The impact of climate change on bee reproduction has been carried out by teams at the University of British Columbia and North Carolina State University, who wanted to track how warm temperatures are impacting our buzzing friends.

“We think honey bees can help us track how climate change is making it harder for insects to reproduce,” explains biochemist and lead author of the paper Alison McAfee. “Terrestrial insect populations are declining around the world. Heat stress, like what can happen during heat waves, partially sterilizes [insects] by damaging their sperm.”

First McAfee’s team exposed queen bees to simulated heat waves, noting a spike in specific proteins in their bodies. Then the researchers used this as a benchmarker to create a diagnostic lab test. In other words, the team made a set of signifiers for heat stress which could then be used when examining new specimens, to see if an insect had been exposed to heat.

Heat stress can cause infertility in a range of species.Pixabay

Heat stress has been found to impact other species’ reproductive abilities too. Scientists at Western Sydney University found that merino ewes and koalas “experience chronic stress as a result of extreme heat, and research indicates that it may also be affecting their ability to breed,” says lead researcher Dr Edward Narayan.

Because bees are crucial pollinators, they are essential parts of our ecosystem. This means protecting their fertility is vital for the food supplies we rely on. However, the findings have implications beyond just the birds and the bees, for bees.

Heat waves are damaging bees’ sperm, making it harder to reproduce.

“We are looking for signs of heat stress in queens as an indicator of what’s going on in the environment,” says McAfee. “If we start seeing signs of heat stress in honey bees, that's when we really need to be worried about wild insects, which don't have stewards like beekeepers, and are often solitary, making them more vulnerable to extreme temperatures.”

In fact McAfee hopes to be able to collaborate more with beekeepers around the world, as queen bees are usually replaced every couple of years by keepers. McAfee wants to use these queens in lab tests to monitor whether they have experienced heat stress in different environments as the climate changes.

What can we do to help?

Despite the enormity of this situation, there are practical things we can do to help. More generally, we can work to ensure we are incorporating sustainable and eco-friendly choices throughout our lives, to help minimise our respective carbon footprints.

But if you want to help bees specifically, there are easy ways we can help them directly.

“The bees that really need our help are the wild bees, like bumble bees, leafcutter bees, and sweat bees,” explains McAfee. “They don't have beekeepers to care for them and are often suffering from habitat loss, leaving them with too few places to forage or build nests.”

McAfee says giving wild bees places to live is crucial when it comes to supporting them.

“The bees would actually love it if you left your yard in a mess,” she says. “Lots of them nest in old sticks, crevices, or small burrows in the dirt, and flowering weeds are great forage.

“If you can't do that, then try planting pollinator-friendly flowers using a mix of plant species that are native to your area. The best mixes have varieties that flower at different times, so they provide forage throughout the season.”

Interestingly, as with other animalsthriving during lockdown, bees have been no different. McAfee explains, “they’ve actually benefited from the pandemic because more green space is being left unmanaged, letting the weeds flourish like a buffet.”

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