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Researchers study biofuels impact on bird biodiversity

By Kris Bevill | January 11, 2011

Newly published research suggests that cellulosic biofuels are for the birds, literally.

A two-year research project conducted by Michigan State University biologists and funded by the U.S. DOE’s Great Lakes Bioenergy Research Center directly compared the biodiversity consequences of corn, switchgrass and mixed-grass prairie. Researchers found, perhaps not surprisingly, that mixed-grass prairie plots supported a greater number of species than monoculture plantings such as switchgrass and corn. Switchgrass, in turn, fared better than corn in the number of species supported. The results of the research indicate that “there’s a potential for us to have our cake and eat it, too,” said biologist Bruce Robertson, who led the research project as a postdoctoral fellow at Michigan State University. “There’s always going to be a trade-off between how much energy or food we can get out of a crop and how much natural benefit we can get from pollination or biodiversity, but this research shows that we have an opportunity to grow a fuel and restore an ecosystem at the same time.”

While studies have previously been conducted on the potential environmental impacts of certain biofuel feedstocks, the MSU study is the first to directly compare various feedstocks. Robertson said this study focused on corn, switchgrass and mixed-grass prairie because the three feedstocks represent a gradient from annual to monoculture perennial to native and diverse perennials. Researchers compared grassland bird populations in 20 sites of varying sizes for each of the three feedstocks, all located in southern Michigan. In addition to confirming the well-known theory that a diverse plot of feedstock would sustain more biodiversity than a monoculture, researchers also found evidence that a general scientific rule known as the “area effect” came into play. Smaller sections of crop supported a lower number of species, but as the crop area was increased, biodiversity also increased. However, there is a tipping point of sorts. As the crop area becomes increasingly larger, biodiversity begins to decrease. Robertson said this finding is positive for potential cellulosic developers because it shows that larger fields of feedstock would more beneficially impact biodiversity than small patches, so long as they are not so large that they trigger a decrease in biodiversity.

Grassland birds were of particular interest to researchers involved in this study because their numbers have dwindled in recent years, mostly due to land conversion, Robertson said. Nearly twice as many grassland bird species were found in mixed-grass prairie sections than in corn. Switchgrass supported more species than corn, but fewer than mixed-grass prairies. In a paper published in the scientific journal Global Change Biology, Robertson noted that as feedstocks are genetically modified to improve biofuel performance, their ability to support grassland bird populations will likely decrease.

The overall findings present an interesting challenge for cellulosic biofuel developers seeking to produce cost-effective feedstock that also has the greatest ecological benefit. What is the ideal area size for feedstocks that will allow cost-effective operations without going over what Robertson describes as the “hump of biodiversity?” Is it possible to produce feedstock effectively without modifying the feedstock to a point where its ability to sustain other life becomes hampered? Robertson said his research did not attempt to address economic factors surrounding biofuel production from cellulosic feedstocks, but he sees potential for a harmonious existence between fuel crops and grassland birds. “[The paper] doesn’t show that we can definitely do that, that the economics are going to work out, that all of these crops are going to be financially viable from a processing point of view or that the government’s going to be able to sponsor programs that give growers economic incentive to grow fields in such a way that we recommend,” he said. “But this paper shows that we have potential to grow crops in such a way that provide an enormous ecological benefit.”

 The scientific paper, “Perennial biomass feedstocks enhance avian diversity,” can be viewed in its entirety at http://news.msu.edu/media/documents/2011/01/207b0463-17ac-4c31-b03f-c925f84b3566.pdf.