It’s springtime, but all is not well in the world of the birds and the bees. Pesticides and parasitic mites have decimated non-native honeybee colonies, but even more worrisome to some conservation biologists is the decline of native bumblebees populations. At least a quarter of the 46 species in North America are at risk, according to Sheila Colla, a researcher at York University in Canada.
Honeybees were imported from Europe as crop pollinators. Native bumblebees are critical for the reproduction of many native non-agricultural flowering plants, which, in turn, provide food and habitat for other animals.
Colla says habitat loss from agriculture and urban development are the biggest factors in the bumblebee decline, but the spreading use of neonicotinoid pesticides and global warming also play a role, as does a spillover of pathogens from introduced bee species. The plight of the bumblebees was formally acknowledged in January with the first-ever endangered species listing for the rusty-patched bumblebee.
Because bumblebees evolved with native plants, they are the only pollinators for some varieties. They can dislodge stubborn pollen by creating a vibration that shakes flowers until they give up their precious dust. Without bumblebees, some of those plants would go extinct.
“Promoting a diversity of native bumblebees is important for sustainable, resilient ecosystems. Since bumblebees are cold-tolerant, they are important pollinators for early spring flowers. And bumblebees will fly far to visit one particular type of flower. That’s important for the survival of some of those rare dispersed species of plants,” Colla says.
Hotspots for bumblebee diversity include mountainous areas — the Rocky Mountains in North America, the European Alps, and the Tibetan Plateau. The worst losses have been in areas that were previously rich in tall flowers but have been converted to agricultural lands, says Paul Williams, an entomologist at the London Museum of Natural History who is compiling a global bumblebee database.
“The most pressing problem right now is probably to prevent the introduction of exotic bumblebees into many parts of the world for pollination because of the risk of introducing pathogens to populations that are not resistant,” Williams says. “Otherwise, promoting and protecting tall flower-rich grasslands and reducing the application of pesticides are important factors.”
There are simple things people can do to help bumblebees. Since protecting species starts with knowing as much about them as possible, the first step is for people to understand why bees are important. There’s great new research coming out all the time, like this University of Nevada–Reno paper about how bumblebees learn. For a good North America overview, read this 2012 United States Forest Service bumblebee management and conservation strategy, where you’ll learn that California has the second-highest number (26) of bumblebee species in North America after British Columbia (35) and just ahead of Colorado (23).
You can also participate in events like the Denver Botanic Gardens Bumblebee Jamboree (April 22nd) to teach kids about pollinator ecology and to meet people who care about bees — that’s how you build an effective community of conservation advocates.
In the United Kingdom, the Bumblebee Conservation Trust has numerous educational and citizen science events coming up, while, in the U.S., the Project Bumblebee Facebook page is a good information clearinghouse.
The next step is helping scientists pinpoint where the bees are abundant or where they may be declining. Williams says citizen science is a critical part of the effort.
In North America, Colla says, bumblebee sightings can be reported via bumblebeewatch.org through a simple four-step process. “That will give us the best scientific data for the long term,” she says. The U.S. Phenology Network also watches for bumblebees as part of its efforts to track nature’s calendar: measuring and recording when cherry trees bloom, when robins build their nests, or when leaves change color in the autumn. Knowing when bumblebees start appearing is important to understanding how they may be responding to global warming.
As long-distance flyers, bumblebees are important pollinators for dispersed and rare flowers, and they can shake stubborn pollen out of tiny flower parts by vibrating their body so hard that the entire plant shakes.
Carder bees (Bombus pascuorum) are important pollinators for early and late-blooming plants because they are tolerant of cold temperatures when other insects are dormant.
The Xerces Society is leading the charge for bumblebee conservation in the States. Citizen science is also an important part of that group’s work, with data from observers all over North America helping to plan conservation strategies. The Xerces Society also offers information on how people can become good stewards of bumblebee habitat by advocating at community planning meetings or simply taking action in their own backyard and in community parks.
Addressing how large-scale agriculture will affect bumblebee populations will probably require policy-level changes, but individuals and communities can make a big difference in residential and urban areas.
Cropped green lawns are actually ecological deserts, so converting millions of backyards — or at least parts of them — to native habitat would immediately create millions of new acres of bumblebee habitat. In the U.K., a national 10-year conservation strategy offers property owners incentives to create bumblebee habitats while encouraging rail and road authorities to maintain stretches of bee-friendly wildflowers in their rights-of-way. Some towns in Scotland and France have started replacing the bedding plants in traffic roundabouts with native bee-friendly plants.
These local and regional fixes can work: A large area of protected open space with native vegetation in and around Boulder, Colorado, is probably a big part of the reason a recent survey showed populations of all 22 known species in the area are holding steady.Bumblebees in Colorado gathering pollen from thistles. (Photos: Bob Berwyn)(Photo: Bob Berwyn)
Colla says the most useful actions people can take are to preserve native habitat and to plant native flowers — especially those that bloom in early spring and late fall. In vegetable gardens, use heirloom varieties, which tend to have more fragrance, pollen, and nectar. Meanwhile, leaving areas of longer grass, hay, and old logs provides good nesting habitat. In the bigger picture, it’s important to support organic agriculture and to refrain from using pesticides.
To take it a step farther, some people even build nesting boxes for bumblebees and provide supplemental nectar.Losing bumblebees would be a huge blow to global biodiversity. Join in the efforts to save them.