SLU scientists study wild bees to learn why they prefer cities as habitats
In a community garden in central St. Louis, Saint Louis University biologist Gerardo Camilo walked methodically, scanning the plants while holding a butterfly net. Then, he stopped and stared intently at a patch of impatiens.
He was pursuing a bee that was weaving in between the stems of the flowers. In one fell swoop, he swung the net down and clutched the net with a fist to trap the bee inside. He examined his captive with a quizzical expression.
"Wow! I have never seen this in my life," Camilo said. "What the hell are you?"
Camilo and other scientists have found that bee populations are abundant and very diverse in urban areas, compared to rural areas, a finding that could help save endangered bees, important pollinators.
After grabbing the bee, he stuffed the end of the net into a jar and screwed on the lid. The jar contained a chemical that killed the bee, which he will add to his collection of local bee specimens. He then asked his assistant, graduate student Paige Muñiz, to take a look.
"When it comes to identifying stuff, I trust her," Camilo said.
"I think that's a bumblebee," Muñiz said, after studying it.
The two researchers were confused because they had never seen a bee so orange. As it turned out, it was a bumble bee that was heavily coated with pollen.
"She's ready for Halloween," she said, laughing. "Look at that orange. She looks like a little candy corn."
Muñiz and Camilo are collecting wild bees to create a catalog for species that live in St. Louis, Chicago and Detroit.
"We have discovered a disproportionately larger number of bee diversity in St. Louis, compared to the rest of the state," Camilo said.
To scientists that know bees, it's not surprising that more bees are found in metropolitan areas.
"We've known that for years," said Gordon Frankie, an entomologist at University of California-Berkeley. "It's only been recently that people pay attention because of the honey bee."
But it's not entirely clear how urban environments make good habitats for bees. Scientists have strong theories that they're looking into and such research has tremendous implications for agriculture and feeding a growing human population.
"Many [wild bees] are actually far better pollinators for a lot of our crops than honey bees are," said Ed Spevak, curator of invertebrates at the Saint Louis Zoo.
One bee of a wild species could have the pollinating power of as much as 60 honey bees. Some are "specialists," that only pollinate specific plants, like squash bees.
Camilo thinks one reason bees are heading to cities is because they're losing habitat in rural areas. Unlike the honey bee, most wild bee species nest in the ground, preferably near flowering plants.
"The expansion of monocultures has resulted in very little land left untouched," Camilo said. "The less area we have for native plants, the less habitat and the less resources we have for these beautiful, beautiful organisms."
Many wild bee species in Missouri and elsewhere are finding plenty of places to nest and forage in cities.
"In cities, you have a lot of people, but you also have people who love flowers and bees love flowers, so there is some synergy there," said Kevin Matteson, a pollination biologist at Miami University in Ohio who has tracked bees in Chicago and New York City.
Within St. Louis, Camilo has discovered that bee diversity is much higher in north St. Louis. The numerous vacant lots in that part of the city make ideal habitats for wild bees.
"People would say [the lots] look unkempt because you have all this leftover vegetation," Camilo said. "Well, bees like that because it provides habitat, refuge, and nesting sites."
A recent paper that he and other scientists published in the journal Conservation Biology also noted that bee diversity tends to be greater in poor socioeconomic areas.
"You have 20 bucks in our pocket. Are you going to buy pesticide for your sidewalk and driveway? No, your preoccupation is putting food on your table than meeting some aesthetic level that's irrelevant to your life," Camilo said.
Last year, researchers in Massachusetts also found that mowing lawns less frequently could substantially raise pollinator diversity.
After interviewing many urban gardeners, Camilo also found that the produce grown in gardens in north St. Louis neighborhoods flourished better than the ones on the south side. The reason, he said, is simple. The north side has better habitats for bees, so there's more of them pollinating plants.
Spevak said recognizing that is key to making cities better places for pollinators to thrive.
"Since most of our native bees are solitary, we can't just put them in a box and move them from place to place," Spevak said. "It's all about habitat."
Camilo also is collaborating with the Missouri Department of Conservation on an outreach program to educate city residents about how they can change their gardening practices to promote pollinator health.
"It's causing us to reimagine cities from not biological deserts anymore, but to something that has real conservation, ecological value to declining bee species," said Erin Shank, Urban Wildlife Biologist at the Missouri Department of Conservation. "I've been in this job for 14 years and this is probably the most exciting project I've been involved in."
The state agency has funded a total of $100,000 to Camilo in the last three years to support his research and outreach efforts.
Camilo and Muñiz store the specimens they collect at a Saint Louis University laboratory. There, they look at the bees with a microscope and other magnifying equipment to study biological traits that can give clues to what types of environments and plants the each wild bee species prefers.
"We know for sure that the more floral diversity you have, the more bee species you'll have," Muñiz said. "Other than that, we don't know yet. We still have to analyze the data."
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Clarification: An earlier version of this story misidentified the bee caught in the community garden. Carpenter bees and bumblebees are distinct species.