MISSOULA, MONTANA—New energy development in the United States could take up a land area roughly twice the size of Maine by 2040, according to a new estimate. Building the new coal mines, oil and gas wells, and solar and wind farms needed to meet projected energy production levels could require an additional 175,000 to 250,000 square kilometers of real estate, researchers reported here at the North America Congress for Conservation Biology. Such “energy sprawl” will complicate efforts to preserve wildlife habitat, they predicted.

“There is going to be a very large challenge in siting all of this energy infrastructure,” says landscape ecologist Anne Trainor of Yale University, who is developing the estimates with Joseph Fargione, a science director at the Nature Conservancy in Minneapolis, Minnesota. “But it is important that we understand how much space we might need under different scenarios, and be able to understand the trade-offs related to different energy sources.”

To get that big picture, the researchers built on a similar 2009 analysis that appeared in PLOS ONE. Drawing on official energy forecasts, they explore four scenarios: a “business-as-usual” world that assumes no major changes in energy trends; an “increased oil and gas” future in which those fuels play a bigger role; a “limited carbon” world which includes government curbs on greenhouse gas emissions from fossil fuels; and a “renewables” future that includes expanded solar, wind, and biofuel energy production. They then estimate how much new land would be needed for each energy source through 2040, including infrastructure like roads and transmission lines. A conventional gas well, for example, typically requires 2 to 4 hectares. They made the numbers comparable by converting everything to a common unit, “kilometers squared per terawatt hour” of energy produced.

The largest new energy footprint—about 250,000 square kilometers, or an area roughly the size of Wyoming—was associated with the increased renewable energy future. In part, that’s because solar and wind farms need large areas. But once installed, Trainor notes, these renewable sources can produce power indefinitely without consuming new land, unlike coal mines or oil and gas wells, which eventually exhaust their resource and must be abandoned.

The smallest footprint—about 175,000 square kilometers—was associated with the increased oil and gas scenario. That’s because relatively compact fossil fuel deposits can produce a lot of energy, but only for a limited duration. Once depleted, the miners and drillers must move on.

The limited carbon scenario took a bit more space, about 200,000 square kilometers, while the business-as-usual scenario came in at about 190,000 sq km. Within that total, surface coal mines were the biggest player, cumulatively consuming an area about the size of Maine. “Unconventional” gas wells, such as those that employ fracking technologies, accounted for about 13,000 square kilometers of land; the footprint of conventional wells was about one-quarter that size. Wind energy covered a land area about the size of Delaware (6400 square kilometers), while biofuel crops and forests would cover Connecticut (about 14,000 square kilometers).

The researchers are still crunching the numbers, but even their preliminary results should help policymakers, says range ecologist Brady Allred of the University of Montana, Missoula, who is conducting his own analysis of oil and gas land use in the western United States. “Combining things into a single metric really helps you compare the footprints and see the potential trade-offs,” he says. Renewable energy, for instance, “is clean and green, but it has a bigger footprint. It’s important to take those kinds of issues into account.”

Yale’s Trainor, meanwhile, is hoping to extend the analysis to consider other factors, such as the greenhouse gas emissions produced by each kind of energy production. The goal, she says, “is to understand how these scenarios play out on the landscape and in other ways.”