Biofuel crops could carpet an area the size of Indiana by 2030. Credit: Getty

Millions of hectares of land will be needed to meet growing energy demands in the United States over the next two decades, according to new 'energy sprawl' estimates. The researchers behind the study say that biomass production for fuel or electricity generation will have the biggest impact on landscape and habitats.

The broad analysis of potential US energy and climate-mitigation scenarios compared the land and habitat impacts of various energy mixes — from nuclear power to biofuels — resulting from an array of policy options. The study is published this week in PLoS ONE1.

In a supplement to the paper, the authors re-ran their estimates to take account of the likely impact of the American Clean Energy and Security Act of 2009, also known as the Waxman-Markey bill. The bill, which is awaiting approval by the US Senate, includes a cap-and-trade system to regulate greenhouse gases.

The researchers estimate that regardless of whether the Waxman-Markey bill were enacted, the amount of land affected by energy development by 2030 will be between 21-70 million hectares — an area which is, even at its lower bound, about the size of the state of Wyoming.

"A cap-and-trade bill may have some incremental effect in increasing energy sprawl, but most of the development that's going to happen is because of other laws that are already in place," says study author Robert McDonald, a landscape ecologist with The Nature Conservancy, a non-profit environmental organization based in Arlington, Virginia.

Those other laws include the US renewable fuel standard, which requires that the volume of renewable fuel blended into gasoline is increased from 34 billion litres in 2008 to 136 billion litres by 2022. That increase will require an area of between 19 and 31 million hectares — the largest component of McDonald's projected energy sprawl, despite the fact that biofuels are expected to comprise less than 5% of the country's total energy budget.

The US Energy Information Administration predicts that ethanol derived from corn alone might reach annual production levels of 39 billion litres by 2030. McDonald and his colleagues calculate that this would require more than 9 million extra hectares of land to be planted with corn (maize), an area about the size of the state of Indiana.

McDonald notes that not all of this development will necessarily result in habitat loss or affect virgin habitat. For instance, a farmer who grows one type of crop on his land might simply switch to growing corn for biofuels.

Climate or habitat?

Although there is an extensive body of data about the way that climate change could affect habitats and biodiversity, few studies have evaluated the impact of future energy development on land-use and habitat, says Jimmie Powell, a policy expert at The Nature Conservancy and a co-author of the study.

"If we are to prevent serious, damaging climate change, it will require one of the largest land-use changes in the history of the country," says Powell. "Because the change is so big, it's important that we do it carefully to minimize the environmental impacts of these new energy resources."

The authors outline several ways of reducing carbon emissions while limiting energy sprawl. These include energy conservation to reduce the need for additional energy and land use; proper siting of energy projects to reduce their impact on important habitats and endangered species; and a flexible cap-and-trade system that allows for offsets that would provide incentives for low-carbon-emitting activities.

Martha Groom, a conservation biologist at the University of Washington, Bothell, who was not involved with the study, agrees with these conclusions. "I'm someone who believes that habitat change is as big a threat to our world today and our society as is climate change," she says.

Groom is optimistic that policies can be shaped to promote options that have the least impact on land use and habitat change, such as algae for biofuels, but adds that boosting energy efficiency is crucial. "We can't emphasize enough that energy conservation may end up being one of our cheapest ways to do this."