ISSUES IN ECOLOGY NUMBER SEVENTEEN SPRING 2013 Ecological Dimensions of Biofuels Clifford S.Duke,Richard V.Pouyat,G.Philip Robertson,and William J.Parton Introduction Policy makers are increasingly looking to are liquid fuels derived from a variety of hio.biofuels ti) ources that contribute to mate change ng G biodiesel)and man- lending of et 1 with gasoline. d of incentives and tariffs.have driven a worldwide s are examining ow pot ided o mtganeiinonicromctbihnesodld and sugar canc,but the variety of materials is ide biofuelus on th the hanol,which of h ofuels pro g the targets for biofues report some of the uncertaintics about those effects able be unc vation and WWe first summarize the direct and Energy Act of 200 (known as the arn Bill), irect effects of b centi b)pro. Fuel Srandard (RFS).the Energy .biodiversity.including the effects of called for a and conversion,monoculture agriculture nvasive ofuel an the We pror se eleme tof an integrated researc ate.The program that uncertainties. 2 esa The Ecological Society of America.esahq@esa.org 2 esa © The Ecological Society of America • esahq@esa.org Introduction Policy makers are increasingly looking to renewable energy sources as environmentally friendly and sustainable replacements for fossil fuels used for transportation. Biofuels, which are liquid fuels derived from a variety of sources—for example, row crops, trees, algae, and food waste— appear to hold promise to reduce our dependence on fossil fuels and to reduce net emissions of greenhouse gases (GHG) from mobile sources that contribute to global warming. Many countries, including the United States, have set targets for biofuels production (ethanol and biodiesel) and man￾dated the blending of ethanol with gasoline. These policies, combined with economic incentives and tariffs, have driven a worldwide expansion in the production of various crops for use as transport fuels. At present, biofuels are primarily derived from a small number of plant materials, or feedstocks, primarily corn and sugar cane, but the variety of materials is expanding. Worldwide biofuel use for transport is expected to nearly double by 2017 over 2005–2007 levels.1 A target adopted by the European Union (EU) in 2009 requires 10% of fuels for transport to be from renewable sources by 2020. In the U.S., ethanol, which accounts for more than 99% of biofuels pro￾duced, is made almost exclusively from corn grown on prime agricultural land. With rising demand and legislative targets for biofuels, increasing output will require boosting yields of existing crops, bringing more land into bio￾fuel crop production, and/or developing new feedstocks (see Box 1). Provisions in U.S. legislation, including the U.S. Energy Independence and Security Act of 2007 and the Food, Conservation and Energy Act of 2008 (known as the Farm Bill), set new targets and incentives for biofuels pro￾duction. In amending an earlier Renewable Fuel Standard (RFS), the Energy Independence and Security Act called for a nine-fold increase in renewable fuel produc￾tion by 2022. Gasoline for road transportation would have to consist of 20% biofuels by this date. The U.S. Environmental Protection Agency (EPA) in 2010 issued new production targets for various biofuels and detailed sched￾ules for meeting them (see Box 2.) The 2008 Farm Bill increased targets in the U.S. and established tax credits, grants, and other pro￾visions to encourage the expansion and use of transport biofuels, with new emphasis on fuels derived from cellulosic sources. If produced in a sustainable fashion, biofuels could reduce demand for fossil fuels, in turn reducing needs for imported oil and mitigating climate change by limiting GHG emissions. As with any agricultural crop, however, bio￾fuel crops can affect water supply and quality, soil biogeochemistry, land use, and biodiver￾sity. Erosion, nutrient runoff, habitat loss, the loss of beneficial species, and the spread of invasive species are all potential risks of expanded production. Scientists and policy makers are examining how potential adverse effects on natural resources can be avoided or mitigated in order to meet biofuels production goals while enhancing environmental, social, and economic sustainability. Research has also focused on the impacts of various economic policies intended to stimu￾late biofuels production, the economics of growing crops for transportation fuel, and the potential impact on worldwide food produc￾tion. As the need for food increases with a burgeoning global human population, biofuel crops compete for arable land and may lead to higher food prices. While acknowledging the potential economic and social implications, the objectives of this report are to summarize the environmental effects of biofuels, illustrate some of the uncertainties about those effects, and identify topics for an integrated research program that could reduce uncertainties in planning for sustainable biofuels production. We first summarize the potential direct and indirect effects of biofuels production on GHG emissions and soil carbon. Subsequent sections describe impacts on water use and quality, biodiversity, including the effects of land conversion, monoculture agriculture, invasive species, and the potential tradeoffs between biofuel energy yield and biodiversity. We propose elements of an integrated research program that could reduce the identified uncertainties. Finally, we link a set of princi￾Ecological Dimensions of Biofuels Clifford S. Duke, Richard V. Pouyat, G. Philip Robertson, and William J. Parton ISSUES IN ECOLOGY NUMBER SEVENTEEN SPRING 2013