Hot Days Are Hard on Bees. Here’s How You Can Help Them Cool Off.
Bees play a crucial role in pollinating plants, but soaring temperatures can put them under stress. Here’s how to make your backyard a cooling bee-friendly oasis.
Humans aren’t the only animals feeling the heat this summer. Even bees can face significant strain in sweltering heat, which can have far-reaching implications for ecosystems and agriculture.
Studies have found that heat waves can make the plant pollen that bees depend on to survive less nutritious. It can also make bees more sluggish when finding food. These things combined can seriously threaten the ability for plants to reproduce.
While air conditioning an entire yard is impossible, there are still steps you can take in your local natural spaces to make life more bearable for all species of bees—including honeybees, bumblebees, mason bees, and sweat bees—in the ever hotter months.
How Extreme Heat Affects Bees
When temperatures climb, pollination takes a back seat to survival for bee populations. Instead of zipping from flower to flower, many bees use their energy to stay cool.
When a honeybee colony overheats, the workers band together to spread water along the honeycomb and help it evaporate by fanning their wings. Bumblebees, too, cool their nests by vigorously flapping their four wings.
And as male bees zip around looking for mates, high temperatures can kill off their sperm and limit their fertility. This is not unlike humans, who can similarly face temporary reduced fertility if they spend too much time relaxing in a hot tub or sauna.
Solitary bees, which include the majority of the world’s 20,000 bee species, have fewer strategies for coping with heat.
“It is a single hard-working mom who is caring for her brood,” says Christina Grozinger, an entomologist at Pennsylvania State University. “If the adult bee gets too hot, it can lose muscle control and no longer be able to move.”
However, much remains unknown about how bees respond to extreme heat. The effects of high temperatures have been studied in fewer than 1 percent of species, per Grozinger, and most research has focused on the immediate effect of heat, like when it is so hot the bees can no longer stand up.
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After a few hours baking in intense heat, the adults will succumb. Baby bees have it even tougher, since their larval physique prevents them from fleeing when it gets too hot.
But the heat doesn’t just slow bees down. It can also create a dangerous trade-off as they run short on food.
“If it is too hot, the bees will not leave the nest to forage,” says Grozinger.
How Rising Temperatures Affect Pollination
When the work of bees is interrupted, their entire ecosystem can suffer the effects.
Bees are heavily dependent on the flowers that sustain them but rising temperatures have led to many missed connections for the plants and their pollinators. Warmer winters and springs can make flowers bloom earlier or bees awaken from hibernation too soon, before the partner they depend on is ready.
But even if the timing still works out, heat stress can cause a plant to produce fewer flowers or have scant stores of nectar and pollen for hungry bees on the hunt for a meal.
“We need much more information on how different bee species respond behaviorally to extreme heat under natural conditions,” Grozinger says. This includes whether they change the time of day they go look for food or pick different places to make their nests.
Outside of extreme events like heat waves, steadily rising average temperatures are altering where different species can thrive. Many animals and plants are shifting their ranges northward or escaping to higher elevations to find chillier climes to call home. But this might not be doable for all creatures.
“Studies in bumblebees suggest that these species are not moving north or to high elevation areas,” Grozinger warns, meaning they “might be trapped in habitats that are becoming too hot for them.”
Overall, climate change represents one of the top threats to bees, right up there alongside habitat loss and pesticides. Even outside of heat, changing weather patterns brought about by climate change can interfere with a bee’s life. Grozinger’s research group has found that rainier springs in the Eastern U.S. lead to fewer springtime bees out and about, likely because conditions are too harsh for them to venture out and find food.
How You Can Help Bees Keep Cool
Studies have found that the existence of small-scale variations in things like temperature and humidity—known as microclimates—can be beneficial for insects and even help combat the negative effects of extreme weather. Creating such microclimates in your yard can help bees cope with hot days, as studies show bees and other pollinators prefer shaded flowers when temperatures are high.
“Having habitats with flowering trees, flowering shrubs, and flowering perennial and annual plants can allow bees and other insects to find the temperature conditions that are best for them for foraging and nesting,” Grozinger says.
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Grozinger also recommends providing a variety of cuisines for the insects to enjoy.
“Having a diversity of flowering plants and habitats in as large an area as possible will help our bees find the resources they need,” Grozinger says. “If you can work with your neighbors to plant trees, shrubs, and flowers that bloom at different times of day, have different colors, shapes and scents of flowers, and are well-watered, it would provide a wonderful haven for bees.”
Most solitary bees nest in the ground, Grozinger notes, so making sure your yard has shady soil is a good way to make sure they can find refuge when the thermometer starts climbing.
Access to water is important too, but Grozinger cautions that any liquids you offer should come in a shallow dish with some rocks in it so that the bees can’t slip in.
Whatever the weather, if your yard has a healthy variety of plant life, easy access to water, and plentiful shade, bees will be sure to come buzzing along.
