Projecting pollinator response to bioenergy production
EAST LANSING, Mich. – Bioenergy policies based strictly on economic or energy considerations that lack attention to biodiversity impacts will likely have serious consequences for the conservation of wild bees and their pollination services, according to a newly published scientific journal paper.
The new research explores how bees might respond to two contrasting bioenergy production scenarios: annual row crops such as corn or soybean, and perennial grasslands such as switchgrass or diverse prairie. The projections are strikingly different—pollinators are expected to have a highly favorable response to grassland bioenergy production and an unfavorable reaction to increasing amounts of annual row crop production.
Michigan State University (MSU) postdoctoral scientist Ashley Bennett, lead author of the paper “Modeling pollinator community response to contrasting bioenergy scenarios,” published in PLOS-ONE, collaborated on the project with scientists at MSU and the University of Wisconsin-Madison, all members of the Great Lakes Bioenergy Research Center (GLBRC). The researchers used field observation data to develop empirical models for predicting the abundance, diversity and community composition of flower-visiting bees on the basis of land cover.
Their findings suggest that 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, converting 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.
“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,” Bennett said. “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.”
It is important that policies helping to advance bioenergy production do not overlook the possible negative impacts on biodiversity and ecosystem services but rather balance the potential implications, Bennett said.
“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 Rufus Isaacs, who is also leading a national research effort to find alternative pollinators for specialty crops, was involved in the project. He said transitioning the landscape into either annual or perennial biofuel crops will affect wild bees, which annually contribute $3.1 billion in pollination services to U.S. agriculture.
“Field-level research has found bee abundance to be three to four times higher within perennial grasslands than in corn fields; at the landscape level, pollinators respond positively to increasing amounts of natural area and negatively to landscapes dominated by annual agriculture,” said Isaacs. “It is paramount that we identify how bioenergy crops affect biodiversity to develop sustainable biofuel policies appropriate for regional implementation across the United States.”
The methods and models developed in the study can also help identify land thresholds to maximize biodiversity conservation and target landscape areas where perennial bioenergy plantings could facilitate pollination services. But Bennett and the other scientists involved with the study acknowledge that unless there are policy changes to improve the market value of perennial grassland bioenergy production, annual commodity crops will continue to be the more popular choice, despite negative consequences on ecosystem services.
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