Farmers are acutely aware that honeybees are dying. Their concern is justifiable, as up to 40% of the food we consume is pollinated by bees. Survey data generated by the U.S. Department of Agriculture indicates that winter losses for commercial beekeepers are around one-third of the bee population since 2007. Overall, these losses far exceed the historical rate of 10% to 15% and threaten beekeepers and the many agricultural crops that rely upon pollination for production.
According to a study by the United Nations Environment Program, the contribution of these pollinators to the production of crops used directly for human food has been estimated to be worth $207 billion globally-nearly 10% of the total value of food production.
While still under debate, the most likely cause of the bees' disappearance, also known as colony collapse disorder (CCD), is thought to be a combination of Varroa mites, insect diseases, stresses brought on by monocultures of crops, migratory beekeeping and pesticides.
Mark Winston, biologist and director of the Center for Dialogue at Simon Fraser University, wrote in a New York Times column, "A typical honeybee colony contains residue from more than 120 pesticides. Alone, each represents a benign dose. But together they form a toxic soup of chemicals whose interplay can substantially reduce the effectiveness of bees' immune systems, making them more susceptible to diseases."
Honeybees, a non-native species, are currently used almost exclusively for plant pollination in the United States, and are also the most vulnerable to CCD. But studies have found that, by taking advantage of several other species of bees, growers could combat the effect of CCD while also boosting crop pollination and increasing profits. For example, recent research from North Carolina State University found that blueberries visited by a variety of native bee -species produce more seeds and larger berries, giving farmers significantly higher yields of fruit per acre.
"We wanted to understand the functional role of diversity," said Dr. Hannah Burrack, an associate professor of entomology at N.C. State and co-author of the study. "We found that there is a quantifiable benefit to having a lot of different types of bees pollinating a crop."
In the blueberry fields, the researchers identified five distinct groups of bee species: honeybees, bumblebees, southeastern blueberry bees, carpenter bees and a functionally similar collection of species that they called "small native bees." The researchers discovered that, for each group of bees added, the farmers' yield increased by $311 per acre.
Crop yields-and profits-can be maximized if considerable acreages of cropland are left uncultivated in order to support wild pollinators, they found. According to the study, farms are often intensively managed, but there are usually unmanaged landscapes nearby that could encourage pollinator diversity. With highbush blueberry, for example, wild-bee diversity improves ecosystem functions by enhancing pollination in variable climate conditions. In other words, while honeybees will only pollinate in certain sunny conditions, wild bees are not as picky and will pollinate plants on cloudy days, too.
Winston conducted a similar study and also concluded that a variety of wild plants in the vicinity means a healthier, more diverse bee population, which contributes to pollination. He found that farmers planting an entire field would earn about $27,000 in profit per farm, while those who left a third of the area unplanted for bee nesting and foraging would earn $65,000 on a farm of similar size.
The challenges posed by bees "remind us that we can manage too much," Winston said. "Excessive cultivation, chemical use and habitat destruction eventually destroy the very organisms that could be our partners."