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Stop and smell the roses ... before the fragrance is gone

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Flowers grow along a busy street in Manhattan, New York. (Photo by Danielle Gaines)

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Flowers grow along a busy street in Manhattan, New York. (Photo by Danielle Gaines)

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Flowers grow along a busy street in Manhattan, New York. (Photo by Danielle Gaines)

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Flowers grow along a busy street in Manhattan, New York. (Photo by Danielle Gaines)

Magenta and red tulips, deep golden forsythia, green vegetable sprouts, pinkish-purple bleeding hearts and purple hyacinths. Spring has sprung in Carol Michel’s Indianapolis garden.

Michel, a lifelong gardener, loves floating around her yard tending the hundreds of plants that wrap around her neatly manicured lawn. She loves the sights, sounds and especially the scents in spring and summer.

But while Michel gardens primarily for pleasure, her hobby may also hold the key to solving a new air pollution problem.

Earlier this month, a research team at the University of Virginia concluded that increased air pollution is dulling the airborne fragrance of flowers, which may help explain why bee populations are disappearing across the country. Unable to smell their way to sources of pollen, the bees are dying off.

“These insects are a tremendous and valuable service to human beings,” Jose Fuentes, a professor of Environmental Sciences at the University of Virginia and one author of the study, said. If something isn’t done: “Our growers will be impacted. Our farmers are losing.”

But the researchers also found a possible solution. Bees might be able to overcome the decreased fragrance cues and find their way to food by sight instead, with increased garden patches in urban and suburban areas. The gardens can serve as visual beacons for pollinators, and if spaced close enough together, eliminate the problem of shorter scent trails.

All of Michel’s plants are pollinated naturally by the wind, bees or other insects and she said she has experienced no problems with pollination. This is likely, she believes, because she plants particularly fragrant and visually conspicuous flowers – she has nine lilac shrubs and trees.

Fuentes, whose study was published in the Journal of Atmospheric Environment, used mathematical models to estimate how far fragrance molecules could travel. Fuentes and his team concluded that scent trails traveled up to 1,200 meters in preindustrial times. Today, those same scents may waft for only up to 300 meters in urban pollution, before bonding with ozone and other pollutants and losing their punch.

The result is a potentially calamitous cycle in which bees fail to locate plants, leaving them unpollinated and causing a decrease in both populations. Bees pollinate every third bite of food in the U.S., according to the American Beekeeping Federation.

In the U.S., bees are necessary to pollinate about 30 percent of crops including almond, apple, avocado, cotton, pear, raspberry and tomato. Should the bees all die, farmers will have to find a new way to pollinate the $4 billion to $6 billion worth of crops that are currently pollinated naturally in the United States, according to the Ecological Society of America.

Already one grassroots bee-saving gardening movement stands ready to help out. Gretchen LeBuhn, a biology professor at San Francisco State University, has enlisted 23,000 gardeners from all 50 states and all Canadian provinces to take part in the “Great Sunflower Project.” LeBuhn sends a packet of seeds to citizen scientists, who record how long it takes for five bees to visit the flower after it has bloomed.

“Native bee populations are viewed as an insurance policy for healthy ecosystems,” LeBuhn said. “We are enlisting regular people to determine where they are doing well, neighborhood by neighborhood.”

Her volunteers provide critical information about their surroundings, she says. In one neighborhood, five bees might come to pollinate in five minutes, but it will take 30 minutes in other places. With these variables, LeBuhn hopes to learn which urban areas support healthy bee populations and how to improve those that don’t.

LeBuhn says she will be considering Fuentes’ new research when doing her analysis at the end of sunflower season.

“If we had to pollinate all of our tomatoes by hand, they would cost a lot more,” said LeBuhn.

The prospect of planting a sunflower or starting a garden can be intimidating to some, but there is nothing to worry about, Michel said.

“Some people fear as soon as they touch a plant, it is going to die,” Michel said. “They just need to go out and do it and see that things will grow.”

In addition to flowering plants, Michel operates several raised vegetable gardens that yield tomatoes, eggplant, onions and more, considerably cutting her summer grocery bills. She still sometimes worries about whether her long, winding squash blossoms will be successfully pollinated. And the new research troubles her.

“It’s not just the home gardener that could be affected,” she said. “Agriculture in the entire country could change.”

E-mail: dg2410@columbia.edu