Bee populations have rapidly been declining all around the world, due to pesticides, parasites, and climate change. Now, researchers have discovered one of the reasons why bumblebees are disappearing – global warming’s effect on flowering times.
Scientists at Florida State University studied three species of bumblebee in the Rocky Mountains in Colorado, looking at both the direct and indirect effects of climate change. Their findings are published in Ecology Letters.
"Knowing whether climate variation most affects bumblebees directly or indirectly will allow us to better predict how bumblebee populations will cope with continued climate change," said Jane Ogilvie, the study’s lead author, in a statement. "We found that the abundances of all three bumblebee species were mostly affected by indirect effects of climate on flower distribution through a season."
The researchers found that up in the Rocky Mountains, global warming is causing snow to melt earlier, and flowering seasons to last longer. This might sound like a good thing for bees, but Ogilvie and her team found quite the opposite. Extended flowering seasons meant more days of poor flower availability and a shortage of food overall. Sadly, this lack of good quality flowers is killing the bees.
"When researchers think about flower effects on bees, they typically consider floral abundance to be the most important factor, but we found that the distribution of flowers throughout a season was most important for bumblebees," Ogilvie said.
As the world’s population continues to expand, and the climate is constantly changing, future food security is becoming more and more of a worry. Bumblebees are essential pollinators to us. Along with other bee species, they are responsible for pollinating 70 percent of our fruit, veg, nuts, and seeds. Without them, we’d be in a bit of a sticky situation.
"Declining bumblebee populations should be a warning about the expansive detrimental effects of climate change," Ogilvie said. "Bumblebees have annual life cycles, so their populations show responses to change quickly, and many species live in higher altitude and latitude areas where the change in climate is most dramatic. The effects of climate change on bumblebees should give us pause."
The new results are just one of many pieces of evidence showing how the effects of a changing environment are stinging our bees. Yet it also sheds light on a new problem that might be quite complex to combat.
"I'm afraid that this research shows conservation will be even more complicated than expected," she said. "In addition to the response of the target species, our findings suggest that we should be considering how a species' food resources might be responding to climate change. For bumblebees, in particular, we need to make sure that they have enough flowers available during the entire season."