By now, you've probably heard about the decline of European honeybees, a phenomenon also known as Colony Collapse Disorder (CCD). While researchers still look for a singular cause for CCD, the effect remains the same: Colonies of domesticated bees (Apis mellifera) are mysteriously dying out because bees aren't making it back to the hive.

In my work as an urban naturalist, I've met many people who are concerned about honeybee colonies, but who don't know how to help — short of becoming beekeepers themselves. (Which, given the recent uptick in beekeeper short courses offered throughout the Twin Cities, some people actually do.)

Bumblebees are another story. They, too, are fellow pollinator-symbionts, but though obviously larger sized, they're overshadowed by the reputations of their smaller, honey-making Apis cousins. Nevertheless, bumblebees are important pollinators of many soft fruit crops, tomatoes, peppers, curcurbits, runner beans and wildflowers. Bumblebees can fly at lower temperatures than honeybees, which makes them useful in colder climates.

Interestingly, these miniature bee giants also produce vibrations during flight that releases pollen from tomato anthers; this special ability is appropriately called buzz pollination, and in case you were still questioning the significance of bumblebees, tomatoes grown in glasshouses are typically (and efficiently) pollinated by bumblebees using this method.

Some species becoming endangered
Unfortunately, a few of the known 49 native bumblebee species in the United States are becoming endangered. According to the National Research Council (as cited in a Xerces Society report), populations of wild bees are in a "long-term downward trend." It is not known for sure what the specific cause of their decline is; some bee experts like Robbin Thorp speculate that our native populations acquired some kind of pathogen from commercially reared bumblebees.

For those of us who are not beekeepers, bee researchers, or insect pathologists, what can we do? Surely we can do something to support and conserve bumblebee populations in our urban and suburban landscapes. And there are.

One action is to keep planting flowering perennials to your landscape. Organizations like the U.K.-based Bumblebee Conservation Trust encourage gardeners to not only plant flowering perennial plants, but also to select plants that will produce flowers throughout the entire growing season. In an age where crop monocultures dominate the agricultural landscape and where blacktop and turfgrass dominate urban/suburban  landscapes, lack of forage plants can be a serious problem. The more we plant, the more we create a "mosaic" or patchwork of areas within our urban jungle that bumblebees can find nectar and pollen. Remember, for bees, flowers are more than just pretty — they're food.

Another thing to do is avoid using pesticides — especially the ones that affect insects' nervous systems. If you are a professional grower and need to spray out of economic necessity, that is understandable; if you are a homeowner or hobby gardener, chances are good that there is an alternative that provides similar control at a much-reduced ecological cost. For example, if you have a single apple tree in your backyard, try using timing-specific pest controls such as kaolin clay or tying bags over young apples. If you absolutely need to keep your roses aphid-free, use insecticidal soap instead of an organophosphate. If you simply must (or stubbornly insist on using) conventional pesticides, at the very least avoid spraying flowers. The message here is that synthetic pesticides don't just target pests, they also target bees, as well as your pests' natural enemies; the more you spray, chances are the more you'll rely on spraying.

Creating a bee habitat
Finally, we can create habitat. Like some solitary bee species, bumblebees make nests near the ground or under the ground in existing holes, such as abandoned rodent burrows. In the next month, overwintering bumblebee queens will be emerging and searching for new nesting sites. These nests are easy to create (PDF) using simple and inexpensive materials.

The work we do today to create "nectar pathways" of flowering areas within developed areas of our cities and suburbs, coupled with nesting habitats, may be the help our bee friends need to reverse the downward population trends. And the payoffs may be huge. After all, if some countries around the world are already experiencing food scarcity with normal levels of bees, what might happen to food sources when (and if) populations of bees bottoms out?  Surely we can all agree that we can no longer take any of our bee species for granted. To bee or not to bee is the question we already know the answer to.

Neil Cunningham is a biological control specialist works with insects and native plants and urban youth for the Minnesota Department of Agriculture (MDA), and is currently teaching the course Building Biotic Communities for Experimental College. He is also an independent urban naturalist who writes the blog Green Noise. The views in this article are his own and do not necessarily reflect the views of the MDA. 

Further reading

Bumblebee.org

"Orchard Mason Bees and Nests," by Neil Cunningham

"Saving the Bumblebee," Scientific American, April 2009

"Status Review of Three Formerly Common Species of Bumble Bee in the Sub-Order Bombus" (PDF), by Evans, E., Thorp, R., Jepsen, S., and Black, S.H. (Xerces Society)