Of Sunflowers and Citizens
How are bee populations faring in the United States? A citizen science project will help find out
As insects go, the honeybee has been the media's darling of late. This European species is the primary pollinator of commercial food crops in the United States, so it's not surprising that colony collapse disorder (CCD), the phenomenon devastating populations across the country, has been the subject of both the nightly news and scientific study. But bees native to North America also play an important role in pollination of wild and cultivated plants. These solitary and semisocial species, many of which nest in the ground, are harder to study. And there is no nationwide system to monitor them or to track the effects of CCD on plants. All this adds up to a laundry list of missing information about how our pollinators are doing. As Sam Droege, a biologist with the U.S. Geological Survey's Patuxent Wildlife Research Center, notes, "There are no field guides to bees; about 500 of the 4,000 estimated species do not even have scientific names; there are no published lists except for small study areas; and research on wild populations is skimpy."
Gretchen LeBuhn, a conservation biologist at San Francisco State University, is trying to address the dearth of data. This past spring, she and her colleagues there launched the Great Sunflower Project, a citizen science project designed to monitor and map bee populations across the country. The plan is simple: Volunteers agree to plant sunflowers (Helianthus annuus). These plants are native to the lower 48 United States, they are frequented by many bee species, and they don't get too big. "Anyone can have a bucket with a sunflower in it," LeBuhn says. When the plants flower, the volunteers observe the bees that visit, reporting their samples on standardized data sheets at the project's Web site (www.greatsunflower.org). There are already 30 to 35 thousand participants nationwide, many of whom have begun to send in data.
Before beginning the project, LeBuhn and her team did trial runs to find out what observations people could perform reliably over several months. They first had volunteers sit for 30 minutes and count the bees that came to their sunflowers. But this was frustrating all around: When lots of bees came at once, they were too difficult to count. And when none came in half an hour, LeBuhn says, "people felt like they had let me down." She had to figure out "how to communicate that they hadn't failed"—a quandary the biologist in the field is unlikely to encounter.
LeBuhn decided to have participants measure how long it took for five bees to visit their sunflowers, observing two times each month for a maximum of 30 minutes each time. "People can take their cup of coffee out in the morning," she says, "and if they see five bees in five minutes, they're done. If they see none in 30 minutes, they're still done, and they have the most important data" because the lack of bees indicates spots where populations may be in trouble.
Participants place the bees they see in one of five categories: honeybees, bumblebees, carpenter bees, green bees and "other." Identifying bees to species level can be challenging even for a practiced entomologist, but it's easy to spot the differences between these broad groups—the petite honeybee looks very different from the rotund bumblebee. In addition, she asks volunteers to indicate how comfortable they are with their identifications. If confident and less-confident participants return similar results, the data even from those with low confidence are more likely to be good.
Despite these precautions, in a project with so many participants, it's harder to ensure that reported data are sound. But LeBuhn is prepared: "We expect to throw some data out," she says. The statistical models she is using help to weed out inaccurate samples.
LeBuhn also consulted with Droege, who is well-versed in citizen science: He organized Frogwatch, the USGS's monitoring program for amphibian decline and malformations, and is currently working on an online bee-identification guide and a native-bee monitoring project. "Any national survey of a plant or animal will be expensive," he says, "simply from the point of view of having to pay someone to collect the data. If volunteers can do it as well as or better than a paid technician, then it's a no-brainer."
At the conclusion of this growing season, LeBuhn will start mapping pollinator service across the U.S. This will begin to give a clearer picture of the effects of CCD, and will suggest whether native bees are filling in as "insurance policies" in areas where honeybees are gone. It will also help biologists to track the health of native bee populations. LeBuhn is especially concerned about certain bumblebee species, which seem to be in decline. She is looking for funding to continue the study over 5 to 10 years, to track trends in pollinator service.
As the Great Sunflower Project unfolds, LeBuhn continues to do fieldwork, surveying both rural and urban ecosystems. She and Cynthia Fenter recently completed a study of bumblebees in urban parks. "If you think of what the world will be like 500 years from now," LeBuhn says, "parks are what we'll have to work with" in conservation efforts—so it makes sense to pay attention to these systems. And in a paper published in Biological Conservation last fall, she and coauthor Richard G. Hatfield presented the results of a two-year study of bumblebee populations in 20 montane meadows in the Tahoe National Forest in California. Thomas Seeley, a professor in Cornell University's Department of Neurobiology and Behavior, notes, "For me the most telling and important result of the paper is the finding that a landscape factor (proportion of surrounding land that is meadow), not a patch factor (such as meadow wetness and meadow plant diversity) had the strongest positive effects on bumblebee species richness and abundance." And he sees a broader message: "This study demonstrates the critical importance of knowing an animal's ability to get around when doing conservation planning for this animal."
Bees aren't the only creatures LeBuhn is concerned about. She notes that urban and periurban gardens worldwide provide 10 to 15 percent of humans' food supply—and some of the urban poor get 60 to 80 percent of their food from these gardens. "For women, it's often the only economic contribution they can make to the family," she says—so having a better understanding of pollinators' status and needs in urban environments will help city planners and conservationists.
By balancing fieldwork with citizen science, LeBuhn is demonstrating an emergent, multidisciplinary mode of doing science—one that relies both on traditional research and on engaging the public. It's concerned with ecosystem health and human health, and with recognizing the integral connections between the two. And it demonstrates that, for biologists dedicated to exploring these connections, the solitary endeavor of the carpenter bee and the social goings-on of the honeybee are each useful models—in fact, both may be essential.—Anna Lena Phillips