Seattle Garden Project Sheds Light On The Decline of Bumblebees

Sep 13, 2013
Originally published on September 13, 2013 6:27 am

SEATTLE -- You’ve probably heard about colony collapse disorder, the mystery of honeybees dying in large numbers. And if you've been paying attention to our earlier reports, you may also realize that bumblebees, too, have been hit hard. In the last few decades their populations have declined by as much as 96 percent and their ranges have contracted by as much as 87 percent.

A group of Seattle gardeners are trying to find out what effects the bumblebee decline might have in our backyards. They’re taking part in the Urban Pollination Project, a citizen science experiment started by two University of Washington graduate researchers that will assess how important bumblebees are when it comes to pollinating the food grown in urban gardens.

“Pollinators are super important for ecology and for food,” says UPP co-founder Marie Clifford. “One in every three bites of food that we eat requires pollination.”

Just to clear up any bee confusion, honeybees are more slender and wasp-like and have finer hairs on their abdomen.

Bumblebees, on the other hand, can vary in size but tend to be much larger and fuzzier. Another important distinction is that bumblebees specialize in pollinating certain plants that honeybees don’t pollinate, such as potatoes, blueberries and tomatoes.

That’s why volunteers with the Urban Pollination Project are focused on tomatoes.

Here’s how the experiment works: Each gardener grows three tomato plants. One plant is covered with a net to prevent any bees from pollinating it -- this simulates what the future could look like without bumblebees. The second plant is left uncovered so that any bumblebees that happen to be in the neighborhood are allowed to pollinate the tomato plants.

The third plant is where the tuning forks come into play. A tuning fork vibrates at the same frequency that a bumblebee buzzes. That buzzing causes the tomato flowers to release their pollen.

Next the gardeners waited to find out what kind of tomatoes each plant produced. Not surprisingly, the covered plants produced the fewest tomatoes. The plants that bumblebees were allowed to pollinate produced more tomatoes.

“Not only do you get fewer tomatoes, you also get smaller tomatoes when you don't have pollinators effectively pollinating your crops,” said UPP co-founder Susan Waters.

And the plants that were hand-pollinated with tuning forks produced the most tomatoes. But while gardeners toting tuning forks could do the work bumblebees, Waters and Clifford are quick to point out that this isn’t a viable Plan B.

“Bees are cheap labor,” Clifford says. “If we had to go out and hand pollinate all of these crops it would hugely increase the price of those foods in the supermarket.”

Sarah Sanborn and Sarah Vaira contributed to this report, which was produced in partnership with QUEST Northwest.

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