Increased demand for bioenergy, wind, and solar-power plants may also place additional pressure on land resources. Beyond ethanol-based biofuels, much of the bioenergy used in power generation is likely to come from forest biomass through increased use of harvesting residues and (potentially) increased harvesting. Forest ownership patterns have shifted over the last 20 years as a result of the large-scale disaggregation of the forest-products industry. That shift has increased land-use decisions that are based on maximizing shorter-term economic returns rather than long-term production of forest products (USDA 2006). When combined with more intensive use of forests to meet the demand for a shifting basket of products (largely bioenergy), shifts in forest ownership may have increasing effects on the environment. Thus, to pursue its environmental-protection mission effectively in coming years, EPA will need to expand its efforts to monitor and understand land-use changes.

Energy Choices

Energy choices in the United States—including bioenergy, conventional and unconventional oil and gas production, coal, and nuclear power—all have important implications for the environment through the effects of resource extraction or production, fuel combustion, and waste discharge or disposal. The April 2010 blowout of British Petroleum’s Macondo deepwater oil well illustrated how devastating the unintended consequences of energy development can be; the accident killed 11 workers and led to the largest oil spill in US history and the closure of some fisheries in more than 80,000 square miles of the Gulf of Mexico (NOAA 2012a). The rapid but less dramatic expansion of natural-gas production across the United States has raised concerns about effects on local water and air quality. There are also concerns about greenhouse-gas emissions associated with methane leakage during production and transport, although natural gas is recognized as a fuel that inherently emits less greenhouse gas (about half) than coal when combusted (Jaramillo et al. 2007). The comparative advantages are lost at higher leak rates (that is, the rate at which methane, the primary constituent of natural gas, is lost to the atmosphere during the production, transportation, and use of natural gas) (Alvarez et al. 2012).

Another example is the production of ethanol for use as a biofuel, which has increased rapidly in the last decade because of the desire for energy security and renewable transportation fuels. In 2010, about 40% of US corn production was used as feedstock for biofuel production (NRC 2011). Such agricultural and energy choice practices can have negative environmental effects; increased production of corn as an ethanol feedstock has resulted in increased nutrient runoff and corresponding eutrophication of coastal waters, including the Gulf of Mexico (NRC 2008, 2011). Given current water-use efficiencies, large quantities of water are also required for irrigation and the intensification of agricultural practices can increase erosion (NRC 2008, 2011). Further research is required to develop new perennial feedstocks that would require less tillage and have high

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