EAST LANSING, Mich. — A newly published paper points out that second-generation bioenergy crops may help bees flourish in the surrounding environment.

The paper, published Nov. 3 in the online journal PLOS ONE, compares the effects of bioenergy crops such as switchgrass and prairie grass to annual crops such as corn and soybeans on bee populations, including abundance of bees as well as species diversity.

The researchers, from Michigan State University and University of Wisconsin-Madison, took bee samples at various sites in 2012, in each environment. The bees were gathered at so-called sentinel sites, where sunflowers had been planted. Researchers were careful to take the samples the same proximity to forested land at each location.

The differences in bee abundance were dramatic; there were also differences in bee species diversity, although in the latter case the results were less dramatic. The researchers’ findings suggest the expansion of annually planted bioenergy crops could reduce bee abundance by as much as 71 percent and bee diversity by as much as 28 percent.

In contrast, conversion of annual crops on marginal soils to perennial grasslands could increase bee abundance by as much as 600 percent and bee diversity by as much as 53 percent, according to the paper.

“Our analysis of bee community composition suggested a similar pattern, with bee communities becoming less diverse under annual crop bioenergy production and transitioning toward a more diverse community dominated by wild bees with grasslands,” said MSU postdoctoral researcher Angela Bennett, the lead author.

“Models like the ones employed here are powerful tools to test the implications of bioenergy policies. Our work suggests that policies based strictly on economic or energy considerations might have important consequences for pollinator conservation.”

She explained it’s important that policies helping advance bioenergy production do not overlook the possible negative impacts on biodiversity and ecosystem services but, rather, balance the potential implications.

“Demand for renewable sources of energy has spurred interest in bioenergy crops as a fuel source,” she said. “In the United States, the government mandate to increase biofuel production to 35 billion gallons per year by 2022 is advancing research into the production and sustainability of both first- and second-generation biofuels.

“These contrasting options for biofuel cropping systems have the potential to dramatically alter the types of and perennial vegetative cover in agricultural landscapes, significantly affecting wildlife.”

MSU entomologist and co-author Rufus Isaacs noted bees do not pollinate the switchgrass and prairie grasses in question; however, these grasses confer advantages to the wild bees. The perennial grass plantings also have some flowers in the sites, which the bees use for food, plus they are good nesting sites for many of the wild bees, as they are not plowed.

Honeybees were not counted in calculations as to bee abundance, because growers put them in the environment on purpose. The paper cautions the study results could change if management practices become more intensive.

“Increasing pesticide use to control emerging pests or annual harvest of bioenergy grasslands could affect bees in ways not reflected in our models,” it states.

The authors added the model assumes the proportion of forest remains the same across the landscape, suggesting future loss of forest habitat to agricultural intensification or urbanization could alter model predictions.

The other researchers involved in the study are Timothy Meehan and Claudio Gratton, both of the UW-Madison. Research was funded by the U.S. Department of Energy as part of the Great Lakes Bioenergy Research Center, a joint program between MSU and UW. USDA’s National Institute of Food and Agriculture also funded the lead author’s work on the project.

The paper, called Modeling Pollinator Community Response to Contrasting Bioenergy Scenarios, can be read online at www.plosone.org