Scientists at Northwestern University and the Chicago Botanic Garden conducted a two-year study of the blueberry mason bee (Osmia ribifloris) native to the Western U.S. and Northern Mexico. They found that, when a group of bees was exposed to temperatures predicted for Arizona from 2040 to 2099, 35 percent of them died off the first year and 70 percent the year after, a Northwestern University press release reported.
The results have frightening implications for bees in warmer regions.
“Local bee populations could possibly go extinct in the future because of climate change,” lead author Paul CaraDonna told Newsweek.
Blueberry mason bees build nests in dead tree stumps. To achieve their results, scientists used paint to create nesting environments in Arizona’s Santa Catalina Mountains with three different temperatures. They painted some nests black to simulate warmer temperatures, some nests white to simulate cooler temperatures from the 1950s and some nests with clear paint as a control.
Not only did the bees in the warmer nests die at alarming rates, they were also smaller and emerged from diapause (insect hibernation) in over 50 days instead of just 10 to 15, as is normal.
“This suggests that they are responding to a stressful environment,” CaraDonna told Northwestern University. “Because their emergence times are altered, they now potentially have fewer floral resources available to them as a population, and it might be a lot harder to find mates.”
The study’s results aren’t just bad news for bees in warmer regions. They are also troubling for the plants the bees pollinate.
“Native pollinators are a really important part of what makes nature run smoothly,” CaraDonna said. “It’s estimated that close to 90 percent of all flowering plants benefit from animal pollination. That ends up at around more than 300,000 plant species worldwide.”
The blueberry mason bees are the main pollinators of wild manzanita shrubs. CaraDonna said the bees could move higher up into mountains as temperatures warm, but that would move them farther away from the shrubs and cause problems for both species.
“This mason bee is probably one of the best pollinators for this plant species, so if you take away the pollinator, you might take away the plant in the longer term,” he said. “We need to understand how nature works and see how it responds to important sources of variation. Otherwise, we don’t have the ability to keep it safe.”