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Pollinator problems

 

What works twice as hard as a domesticated honeybee? Its wild, free-living relatives. Much of the food we eat is pollinated by bees, and it turns out that wild bees are significantly more effective than domestic honeybees at causing flowers to produce fruit.

That finding is just one in a set of new studies reinforcing an obvious truth: human-controlled systems cannot hope to mimic all the sophisticated, complex interactions of natural systems.  As we've created giant monocultures of almonds, alfalfa and other crops, we've destroyed the variety of soil types and native plants that once supported an array of wild bee species and other pollinators like beetles, flies and butterflies.

That means food productivity declines and so does ecosystem health in general.  To compensate, farmers often rent honeybees that are trucked in for a few weeks of pollination work (see our 2005 story "Silence of the Bees" describing the life of a migratory beekeeper).  But for several years now, commercial hives have been succumbing at an alarming rate to a malady known as Colony Collapse Disorder. Hence the increasing importance of native bees.

bee.jpg
Adrena nasonii bee

An LA Times story covers a new report in the journal Science:

The proportion of flowers that matured to fruit improved in every field visited by wild insects, compared with only 14% of fields visited by rented honeybees. … "Honeybees cannot replace the service wild bees provide," (Lucas A. Garibaldi, an Argentinean agricultural scientist), said. "Biodiversity in agricultural landscapes matters and can help increase production."

 

Unfortunately, populations of wild bumblebees, blue orchard bees, carpenter bees and the like aren't faring so well. Another new study in Science revisited century-old observations of wild bees and found that more than half of the 109 species recorded had disappeared. As NPR reports:

One possibility might be a loss of nesting sites for these bees. But a changing climate may also play a role.

The bees that disappeared tended to be species that depended on just a few kinds of flowers for food. For those bees to survive, their preferred flowers have to be blooming when the bees start flying and need food. The warming trend might have thrown off that timing.

In fact, says Laura Burkle, an ecologist at Montana State University, if you map the interactions between flowers and bees, they seem more tenuous now. Some flowers may get visited by just one or two kinds of bees, and maybe just for one week.

Even as native pollinators become less reliable, hives of domestic bees continue to die off from poorly-understood causes, such as infestation with varroa mites and contamination with pesticides.  A new long-term study in Science Daily finds that bee colonies infected with a larvae-killing disease called "idiopathic brood disease syndrome" are more than three times more likely to die off than non-infected colonies. The study also found that the risk of colony death was almost as high for colonies in which worker bees have killed off and replaced a damaged queen bee.

Although the solution to the honeybee problem – relying more on native bees – sounds simple, actually making it happen is, of course, not simple.

From the NPR story:

Claire Kremen, a conservation biologist at the University of California, Berkeley, who's a co-author of the first study in Science, says one of the biggest problems for wild bees is the agricultural specialization that has produced huge fields of just one crop.

The almond groves of California, for example, are a sea of blossoms in February. It's a feast, as far as the eye can see, for honeybees that come here from all over the country. "But for the rest of the year, there's nothing blooming," she says.

Planting other flowers in and around these almond groves, maybe as hedgerows, blooming all summer long, would help, she says. Even better would be farms with smaller fields, and lots of different crops flowering at different times. Wild bees, Kremen says, need diversity.

Our 2007 story, "Native Hum," about the importance of native bees to pollinate crops offered much the same advice:

“Bees need a few different things,” said Sarah Greenleaf, a post-doctoral scientist at UC-Davis who found that when wild bees join honeybees on hybrid sunflowers, production is doubled. “They need flowers for food, nest sites and protection from things that kill them. Farmers can plant flowers to provide food when crops are not blooming, modify pesticide applications, and provide nest sites for bees,” Greenleaf said. “And they can leave some natural habitat near farms. There are lots more bees on farms that are close to natural habitat.”

At least there's a tiny coda of good news – an abandoned housing development in LA proves, once again, how resilient the natural world can be. In the early 1970s, the 800-some homes of the wealthy neighborhood Surfridge were removed to make way for the expanding LA International airport. The LA Times reports:

In the decades since, the (El Segundo blue butterfly), a federally protected endangered species, has made a comeback due to the establishment of a 200-acre butterfly preserve managed by the city. Nonnative plants were removed and native buckwheat — where the butterflies feed and lay their eggs — was reintroduced.

Now, more than 125,000 butterflies take flight each summer, unfazed by the constant thunder of jets overhead.

"It's a remarkable recovery," said Richard Arnold, an entomologist who has worked as a consultant at the preserve. "But you've got to realize that insects have a remarkable reproductive capacity if their natural food source is there."

Jodi Peterson is High Country News' managing editor.

Photo of a bee, Andrena nasonii, that researchers found emerged before the majority of spring-blooming plants with which it historically interacted. (Photo courtesy of Montana State University and Laura Burkle).