Wild bees outperform rented counterparts as pollinators

Farmers who watched helplessly as a mysterious disease wiped out millions of domesticated bees they needed to pollinate their crops may have an easy solution: make their crops more accessible to wild insects that do the job free.

Not only are they cheaper, they fertilize blossoms with much greater efficiency, new research shows. After observing bees in hundreds of fields around the world, scientists calculated that free-living bees were twice as effective as domesticated honeybees at prompting flowers to produce fruit. In addition, the proportion of flowers that matured to fruit improved in every field visited by wild insects, compared with only 14 percent of fields visited by rented honeybees, according to a report published online Thursday by the journal Science.

The findings have important implications for agricultural and land-use policies worldwide, said study leader Lucas A. Garibaldi, an agricultural scientist at the National University of Rio Negro in Argentina. Unless habitats for wild insects are protected and nurtured, farmers around the world could suffer drastically lower crop yields.

Scientists have long warned that plowing landscapes into vast, single-crop fields and orchards eliminates the range of soil, wildflowers and other vegetation that is crucial to support multiple species of wild pollinators, including bees, flies, beetles and butterflies. As these insect populations have dwindled, farmers have resorted to using rented interlopers, generally Apis mellifera, during flowering season.

“Honeybees cannot replace the service wild bees provide,” Garibaldi said. “Biodiversity in agricultural landscapes matters and can help increase production.”

Garibaldi and his colleagues from North and South America, Europe, Australia, Africa and the Middle East analyzed data that had been collected in earlier studies based on direct observation of insect activity in small sections of 600 fields in 19 countries. Researchers generally counted insects, flowers and pollen grains over various periods of time on crops that represented different landscapes and management techniques. Some fields were heavily dependent on domesticated bees; in others, wild insects prevailed.

Even in fields dominated by domesticated bees, farmers often get more effective pollination services from native insects, said study co-author Rachael Winfree, a pollination ecologist at Rutgers University in New Brunswick, N.J.

“At 90 percentof farms studied in New Jersey and Pennsylvania, native wild bees are fully pollinating the watermelon crop,” making rented bees unnecessary, Winfree said. But farmers don’t realize this. “They’re thinking they need them but they don’t,” she said.

In California, the $3-billion almond industry spends $239 million annually to rent more than 1 million beehives every year. To get that many pollinators, growers have been renting honeybees — an increasingly expensive practice as colony collapse disorder wipes out bees by the millions, for reasons that remain poorly understood.

In some California orchards, the data showed that pollination by rented honeybees got a significant boost when wild bees were present, possibly because the wild insects prompted the rented bees to fly more frequently among different varieties of trees in an orchard, said Claire Kremen, a conservation biologist at the University of California, Berkeley, who contributed to the study.

However, she noted that most almond fields don’t receive that benefit because habitat for wild insects has been destroyed.