Solitary Bees Face a Double Challenge From Heat Waves and Pathogens

Bees are vital pollinators that contribute to the global economy and food security. However, they are facing multiple threats from climate change and infectious diseases.

A recent study by Penn State researchers revealed how extreme heat waves and a common protozoan pathogen can affect the behavior and survival of solitary bees, which account for over 90% of the roughly 4,000 species of bees in North America.

The Impact of Heat Waves on Bees and Their Pathogens

(Photo : DAMIEN MEYER/AFP via Getty Images)

The researchers conducted an experiment to test how heat waves affect the host-pathogen relationship between two species of solitary bees (Osmia cornifrons and Osmia lignaria) and a protozoan pathogen (Crithidia mellificae).

They exposed the bees to different temperatures and measured their thermal boldness, which is the amount of heat a bee can withstand in order to move to a food source.

They also assessed the growth rate of the pathogen in the bees' guts.

Researchers found that both the bees and their pathogens were negatively affected by heat exposure, but the bees suffered more.

Heat exposure decreased the bees' thermal boldness and their heat tolerance, meaning that they were less likely to forage for food in hot conditions.

On the other hand, the pathogen's growth rate was only slightly reduced by heat exposure, suggesting that it can still infect and harm the bees even in high temperatures.

The experts also found that prior infection by the pathogen made the bees even more vulnerable to heat stress.

Infected bees were less thermally bold and more likely to die than uninfected bees when exposed to heat waves.

This indicated that the combination of heat waves and pathogens can create a one-two punch that can severely impair bee populations.

Also Read: Study Shows that It May Take a Few Generations Before Bees Recover from a Single Exposure to Insecticide

The Implications for Pollination Services and Conservation

The findings of the study have important implications for pollination services and conservation.

Solitary bees are responsible for pollinating many crops and wildflowers, such as blueberries, cherries, apples, almonds, sunflowers, and clover.

They are also more resilient to some stressors than honeybees, such as pesticides and habitat loss.

However, if heat waves and pathogens reduce their foraging activity and survival, their pollination services may decline as well.

This could have negative consequences for the global economy and food security.

According to a 2016 report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), pollinators contribute to the production of 75% of the world's crops and 35% of global agricultural land.

The annual economic value of pollination services is estimated at $235 billion to $577 billion.

Therefore, it is crucial to protect bee populations from the threats of climate change and infectious diseases.

The researchers suggested that some possible strategies include providing shade and water sources for bees during heat waves, reducing pesticide use and habitat fragmentation, enhancing floral diversity and availability, and monitoring and controlling bee pathogens.

Bees are essential pollinators that face multiple challenges from heat waves and pathogens.

A recent study by Penn State researchers showed how these factors can affect the behavior and survival of solitary bees, which make up most of the bee species in North America.

The study highlighted the need for conservation measures to protect bee populations and their pollination services, which are vital for the global economy and food security. 

Related article: Taal Wipes Out Bee Farm in Laguna