Foodies aren’t the only ones swarming cities in search of the best eats. Even bees are going urban to satisfy their taste for diverse, high-quality food—especially as wild habitat becomes more scarce, new research reveals.
Gordon Frankie, an urban entomologist at the University of California, Berkeley, has been studying the foraging habits of native bees in the Guanacaste Province of Costa Rica (map) to find out just how much the pollinating insects are visiting and sampling foods from urban gardens. (See “Beautiful, Intimate Portraits of Bees.”)
The answer: Quite a bit more than expected. It may seem a little counterintuitive, but “urban environments are actually a refuge for bees,” said Frankie, who has received funding from the National Geographic Society’s Committee for Research and Exploration. That’s because cities provide bees with new food resources, especially if native plants have short flowering seasons or are in short supply because of urban sprawl and other land-use changes.
For the past decade, as part of the Costa Rica Bee Project, Frankie and colleagues have been monitoring specimens of the same plant species in both wild forests and urban environments—where they’re often the flashier, ornamental varieties—and recording the bee numbers and species tending to those plants. Costa Rica has 800 bee species; his team has collected 112. They found that in most cases, a plant specimen located in an urban setting attracts as many bee species as does its wild counterpart; occasionally, city specimens actually get more visitors than the wild ones.
Native plants are preferred in both locations, but the bees don’t turn up their noses at non-native sweets. Overall, as many as 80 percent of the native bees observed in wild settings were also visiting the urban gardens, according to the study (which has not yet been published). “That was higher than we expected, and it gave us hope. As more natural areas are disappearing or being impacted by humans, urban areas offer something more stable—people are looking after them.”
The findings support the idea that properly designed urban spaces (meaning, gardens that are planted with particular bee preferences in mind) can not only maintain but even enhance the ability of pollinators to survive and do their jobs. (Also see “Beyond Bees: 4 Surprising Facts About Pollination.”)
What’s not yet clear is whether these insects are nesting in the cities or just commuting in for meals. “Right now we only know they are foraging from urban plants. Do they stay around or go out of the city to nest? We need to know if they merely transition through the city” or stay around to complete their life cycles outside of the wild. If so, the urban gardens are that much more important for the health of the bee population.
Spreading the Bee Buzz
Many of Costa Rica’s hundreds of bee species are crucial pollinators of important crops (such as beans, squash, and watermelons) and diverse native flora. That’s why Frankie’s team, with its plentiful bee data, is now working with biologist Ana Chassoul, of the Universidad Nacional de Costa Rica, to reach out to schools and other audiences about pollinators. The idea is to make more people familiar with native Costa Rican bee species and the plants that support them, and to spread the word that both wild and planted landscapes can help the insects thrive. (Also see “Pictures: Rare Bees Make Flower-Mud ‘Sandwiches.'”)
Meanwhile, he and his Berkeley colleagues are beginning to design the first bee-habitat garden in Costa Rica. The Santa Ana Conservation Center will be used for education and as a model for future pollinator-friendly urban spaces in that country and beyond.
Even in the U.S., where bees are now regulars in the news because of massive declines from colony collapse disorder and other afflictions, native bee species haven’t achieved the status of their honeybee counterparts. (See “The Plight of the Honeybee.”)
“A few years ago most people in the U.S. knew almost nothing of bees, could maybe identify a honeybee or a carpenter bee, but that’s about all,” Frankie said. “Now, everyone is very interested! But native bees are still relatively unstudied.”
Still, some U.S. cities, including many in California (with its 1,600 native bees)—where Frankie’s team is doing similar monitoring as in Costa Rica—are making strides in giving these bees what they need. (See Frankie and colleagues’ bee-friendly guide for California gardeners.)
Botanist Peter Bernhardt of St. Louis University in Missouri said urban environments are going to become more and more valuable to pollinators. (Read more about pollinators in National Geographic magazine.) “As city planners turn to a more restricted use of pesticides, bees should become happy pioneers in cities, encouraging quality projects in horticulture,” he said.
California has led the way in the domestication of some brilliant wildflowers, “which must bring a number of native bees into the city to stay.” And he thinks the data will eventually show they aren’t there just to feed. “After all, many species prefer to nest in dense soil, and we know the lawns in city parks receive a lot of trampling from our shoes. Urban dirt is hard-packed, the way bees like it.”
While managed honeybees do the lions’ share of the pollinating that interests farmers, economists, and policymakers, native insects also pick up a lot of slack. In response, the charge by bee-garden purists in the U.S. has always been to stick to native plants in city gardens, a tall order when in fact urban gardeners use more than 90 percent exotic plants. (Also see “Urban Farming: Growing Food in a Sprawling City.”)
Frankie said that for helping pollinators, that distinction might not be as important as once thought. “Bees will go wherever they can find pollen and nectar. If urban gardens are diverse, bees will visit. We are learning the relationships between particular bees to particular flowers so we can predict the best mix of plants in each environment, and that will include both native and non-natives.”
“It’s true that native bees overall prefer native plants,” said international landscape designer Kate Frey, who specializes in pollinator-habitat gardens. “Having said that, if recommending people only plant native species turns them away from planting bee gardens, we have to compromise. Some ornamentals bloom when there is a dearth of other flowers, so using non-native plants to bridge the gap, to supplement during lean times of native flora, could be a good thing.” (See more pictures of pollinators.)
Overall, Frankie recommends that some 10 percent of urban land—whether in Costa Rica or California or elsewhere—should be dedicated to bee-friendly gardens. “I know that’s a big wish, but the more we plant the right types and numbers of plants, the more bees, and more bee species, we can expect. If we do the gardens right, they will come.”
To make your own garden attractive to native bees, Frey offers these tips:
1. The same flowers that make us happy also support bees. Choose appropriate plants for your climate and soils. Each area of the country has specific plants that will thrive there, and not all plants are bee-friendly. Do your research to discover which plants serve your location, and native pollinators, best.
2. Plant profusely. The more flowers there are, the more food resources for bees. Putting just one plant here and another over there doesn’t support many bees, and doesn’t make for a lovely garden anyway.
3. Plant in patches or repeat the same plant throughout the garden. Native bees and honeybees need at least ten square feet (a square meter) from which to gather floral resources. Collector gardens with one each of various kinds of plants are not going to feed the bees.
4. Try to plan for as many months of bloom as your climate allows. Ornamental plants can help bridge the gaps.
5. Use at least 50 percent native plants, which will also draw butterflies and moths.
6. Offer more variety to pollinators by including annuals, perennials, shrubs, and trees.
7. Make bee nesting habitat part of your garden. Seventy percent of native bees are ground-nesters that need bare ground (without mulch). Thirty percent nest in crevices—wood or hollow plant stems. Gardeners can make bee nest blocks or keep an old tree or snag on the property for these insects.
8. Bees like the warm sun and prefer sun-loving plants to shade plants. So, let there be light and heat in your city oasis!
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