Bees face many challenges – and climate change is increasing the pressure

The extreme weather that hit much of the United States in 2022 isn’t just affecting humans. Heat waves, wildfires, droughts and storms also threaten many wildlife species, some of which are already facing other stresses.

Bees search for water on an outdoor tap in Berlin, Germany, during a heat wave on June 19, 2022. Wolfram Steinberg/picture alliance via Getty Images

I have been researching bee health for over 10 years, with a focus on honey bees. In 2021, I started hearing for the first time from beekeepers about how drought and extreme rainfall affected the health of bee colonies.

Drought conditions in the western United States in 2021 have dried up bee forage – the floral nectar and pollen bees need to produce honey and stay healthy. And extreme rains in the northeast limited the hours that bees could fly in for food.

In both cases, the managed colonies – hives that humans keep for honey production or commercial pollination – were starving. Beekeepers had to give their bees more sugar water and pollen supplements than they usually would to keep their colonies alive. Some beekeepers who have been in business for decades shared that they lost 50% to 70% of their colonies during the winter of 2021-2022.

These weather conditions likely also affected wild and native bees. And unlike managed colonies, these important species have not been given supplements to protect them from harsh conditions.

Each year, the United States Department of Agriculture and the Environmental Protection Agency host federal pollinator experts to share the latest scientific findings on bee and pollinator health, and assess the status of these important insects, birds, bats and other species. One of the clear lessons from this year’s meeting is that climate change has become a daunting new stressor for bees, potentially amplifying already known problems in ways that scientists cannot yet predict but must. prepare.

Climate change threatens bees around the world. In Australia, large-scale bushfires and drought have killed millions of bees in recent years.

The scourge of Varroa mites

Pollinators contribute between US$235 billion and US$577 billion annually to global agriculture, depending on the value of the crops they pollinate. Understanding and mitigating the impacts of climate change on pollinators is key to supporting healthy ecosystems and sustainable agriculture.

Bee health first came to attention in 2006 with the emergence of colony collapse syndrome, a phenomenon where the majority of a colony’s adult worker bees have disappeared, leaving behind their stores of honey. and pollen and a few nurse bees to take care of the queen and the remaining immature bees. . Over the past five years, reported cases have declined significantly. Now researchers are focusing on what beekeepers call the “four Ps”: parasites, pathogens, pesticides and poor nutrition, as well as habitat loss for wild and native bees.

One of the greatest threats to bees in recent decades has been destructive varroa, a crab-like parasitic mite that feeds on the fatty tissue of honey bees. The fat body is a nutrient-rich organ that functions much like the liver in mammals. It helps bees maintain a strong immune system, metabolize pesticides and survive through winter.

These are vital functions, which is why controlling mite infestations is essential for bee health. Varroa can also transmit deadly pathogens to honey bees, such as deformed wing virus.

A bee carrying two Varroa mites, one above his leg and one on his back. USGS

Controlling mite populations is difficult. This requires using an insecticide in an insect colony or, as beekeepers say, “trying to kill an insect on an insect”. It’s hard to find a formula strong enough to kill mites without harming the bees.

Surveillance Varroa requires a lot of skill and work, and mites can develop resistance to treatments over time. Researchers and beekeepers work hard to breed Varroa– resistant bees, but mites continue to plague the industry.

Microdoses of pesticides

Pesticides also harm bees, especially products that cause sublethal or chronic health problems for bees. Sublethal exposures to pesticides can make bees less able to harvest forage, grow healthy larvae, and fight off viruses and mites.

However, it can be difficult to document and understand sublethal toxicity. Many factors affect how bees react to agrochemicals, including whether they are exposed as larvae or adult bees, the mix of chemicals the bees are exposed to, the weather conditions at the time of exposure. application and the health of a bee colony prior to exposure.

Researchers are also working to understand how soil pesticides affect wild, ground-nesting bees, which make up more than 70 percent of the native bee population in the United States.

A bee nesting on the ground (Inaqualis collars) emerging from its burrow. Rob Cruickshank/Flickr, CC BY

Junk food diets

Like many other species, bees are losing the habitat and food sources they depend on. This happens for many reasons.

For example, uncultivated land is being converted to agricultural land or developed all over the world. Large-scale agriculture focuses on mass production of a few staple crops, which reduces the amount of nesting habitat and forage available to bees.

And many farmers often remove pollinator-friendly plants and shrubs that grow around farmland to reduce the risk of attracting animals such as deer and rodents, which could spread pathogens that cause foodborne illness. . Research suggests that these efforts harm beneficial insects and do not increase food security.

As diverse and healthy bee forage disappears, beekeepers feed their bees more supplements, such as sugar water and pollen substitutes, which are not as nutritious as nectar and pollen as bees get flowers.

Climate change is a force multiplier

Researchers don’t know exactly how climate change will affect bee health. But they suspect it will add to existing constraints.

For example, if pest pressure increases for farmers, bees will be exposed to more pesticides. Extreme rainfall can disrupt the foraging habits of bees. Forest fires and floods can destroy bee habitat and food sources. Drought can also reduce available forage and discourage land managers from planting new areas for bees as water becomes less readily available.

Climate change could also increase the spread of Varroa and other pathogens. Warmer fall and winter temperatures extend the period during which bees forage. Varroa traveling on foraging bees, so longer foraging provides a greater window of time for mites and the viruses they carry to spread among colonies. Higher mite populations on bee colonies before winter will likely cripple colony health and increase winter losses.

Studies have already shown that climate change disrupts the seasonal relationships between bees and flowers. As spring comes earlier in the year, flowers bloom earlier or in different regions, but bees may not be around to feed on them. Even though flowers bloom at their usual times and locations, they can produce less nutritious pollen and nectar in extreme weather conditions.

Research that analyzes the nutrient profiles of bee forage plants and how they change under different climate scenarios will help land managers plant climate-resilient crops for different regions.

Create safe beekeeping spaces

There are many ways to support bees and pollinators. Planting pollinator gardens with regional plants that bloom throughout the year can provide much-needed fodder.

Native ground-nesting bees need exposed, undisturbed patches of soil free of mulch or other ground cover. Gardeners can clear land in a sunny, well-drained area to create dedicated spaces for bees to dig nests.

Another important step is to use integrated pest management, a land management approach that minimizes the use of chemical pesticides. And anyone who wants to help monitor native bees can join community science projects and use phone apps to submit data.

More importantly, educating people and communities about bees and their importance to our food system can help create a more pollinator-friendly world.

Jennie L. Durant, Human Ecology Research Associate, University of California, Davis

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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