Last year Kremen and her team recorded a total of 130 species of native bees lured to hedges neighboring 40 different farm fields. Based on historical records, California was once home to as many as 1,600 native bee species, although it is unclear how many of these persist today. A recent study published in the journal Science found that in a span of 120 years, Illinois lost half its wild bee species, largely because of diminished numbers of wild flowering plants. Another study concluded that four species of American bumblebees have lost up to 87 percent of their habitat, slashing their ranks by 96 percent.
Kremen is hoping to prove not just that her hedgerows attract bees, which is already clear, but also that they are increasing the overall number and diversity of bees in the area rather than siphoning bees from elsewhere. “It's possible that you plant this hedgerow and it sucks all the native bees from the landscape,” says Leithen M'Gonigle, a postdoctoral researcher in Kremen's lab. “When your crop is flowering, you don't want the hedgerows to be more attractive.” In other words, the architecture of restoration might matter a lot.
At a research farm owned by U.C. Davis, a giant bed of knee-high plants, some already budding and flowering, has taken root between neatly organized crop rows that run to the horizon. Here Williams is experimenting with forbs—perennial and annual flowering plants—that could appeal to farmers who do not want to deal with the hassle of woody plants on their fields. The nine plant species in Williams's current experimental mix are drought-tolerant, native, and selected to maintain diversity and abundance throughout the season.
Scientists also hope to learn more about how native bees and honeybees interact. In a study published this year researchers from Williams's and Kremen's labs found that honeybees became even more effective pollinators of almond trees in the presence of both various native species and blue orchard bees, a managed species. The more efficiently honeybees work, the fewer are needed to pollinate a given field. The investigators are now studying whether a specific chemical footprint left by the native bees in fact alerts the honeybees to extra competition.
Hedgerows and wildflowers sound like the province of mild-mannered gardeners puttering about in floppy hats. Yet as mundane as the whole thing may seem, restoring native habitat to farmland could represent the start of an agricultural revolution—one that could make much of our food supply more sustainable. No existing technology can pollinate crops. In southwestern China, where a combination of habitat loss, wanton use of pesticides and overharvesting of honey has wiped out bees, workers pollinate apple and pear orchards by hand, transferring pollen from one flower to another with small brushes. Such a massive effort is far too labor-intensive for the U.S., where it would render fruit prohibitively expensive. Bees—not just honeybees but all bees—are our only hope.
One way scientists aim to jump-start this agricultural revolution is with a program called Integrated Crop Pollination, or ICP. Funded by the U.S. Department of Agriculture, ICP consists of a series of options and steps for supplementing honeybees—including expanding habitat, reducing pesticide use and adding in other managed pollinators. Currently several other bee species, such as the blue orchard variety, are commercially available and may help farmers supplement honeybee populations.
ICP began as an idea flitting about the mind of Rufus Isaacs. As the resident blueberry entomologist at Michigan State University, he spends a lot of time among the fruiting shrubs. While researching ways to control Japanese beetles and other blueberry enemies, he began to notice all the bees. Honeybees, yes, but also Michigan natives such as plump B. impatiens bumblebees, hairy-shouldered Andrena bees and small, black Ceratina bees that nest in thin, hollow stems. Isaacs realized that no one really knew which bees, or how many kinds, were out there. So Julianna Tuell, then a graduate student in his lab, set about categorizing them. She found 112 species of native bees zipping through blueberry fields in bloom and an additional 54 species active before and after the flowering.