Strip mining across the mountaintops of Appalachia is scarring as much as three times more land to get a ton of coal than just three decades ago, new research shows.

The data and a series of new maps that track the spread of surface mining across the region suggest that even as the industry has declined, what continues likely has an oversized impact on people and the environment.

If mining companies have to do more blasting and digging for the same amount of coal, that means more dust in the air and more pollution in streams, said Appalachian Voices Programs Director Matt Wasson, who worked on the study with researchers from Duke University, West Virginia University, Google and SkyTruth.

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"This was really the first step in a larger process of digging deeper into the impacts that surface mining has," said Christian Thomas, a geospatial analyst with SkyTruth, a nonprofit that uses satellite imagery to understand human impacts on the environment.

The study, published online in PLOS ONE, a peer-reviewed journal, also provided what Duke researcher Andrew Pericak described as the first year-by-year mapping showing the spread of mountaintop mining across the region.

The team is making the data publicly available for other researchers, including those looking into the health and environmental effects of mining.

Thousands of Square Miles Blasted and Chewed

For decades, surface mining in the mountains of Appalachia has been among the most destructive forms of extracting coal. Mining companies blast away the tops and sides of mountains to get at underground coal seams, then shove the waste rock into valleys and streams.

Between 1985 and 2015, explosives and mining equipment chewed up more than 1,100 square miles in pursuit of coal buried in the mountains in West Virginia, Kentucky, Tennessee and Virginia. The animation below shows how quickly it spread.

This 1985 satellite image shows mountaintop mining across a section of Kentucky, West Virginia and Virginia. The animation below shows how mining spread across that area over the following 30 years.

Satellite images from 1985 to 2015 show how mountaintop removal mining spread across this 12,000-square-mile area of Kentucky, West Virginia and Virginia. Credit: Christian Thomas/SkyTruth

Combining their work with a previous analysis covering the mid-1970s through 1984, the researchers determined that more than 2,300 square miles—about 7 percent of the area studied—had been cleared in connection with surface mining. That's roughly three times the size of Great Smoky Mountains National Park.

Geologists have predicted that as coal companies mine the thickest and shallowest layers of coal, what's left will produce more waste rock, making surface mining more expensive, the authors wrote.

They identified 1998 as a point of inflection. Before then, it took about 10 square meters to produce a metric ton of coal. By 2015, it was up to about 30 square meters.

"It may simply be becoming harder for mining company to extract the coal," Pericak said.

Concerns About Human Health and Climate

Coal production across the United States slid in recent years as aging coal-fired plants were shut down and replaced by new ones burning cheaper natural gas and as state and federal policies promoted cleaner power sources.

The Trump administration, vowing to revive the coal industry, has repealed an Obama-era rule that sought to protect streams from damage due to mining, and it has been considering ways to increase coal burning, but there has been little change in production in Appalachia.

Coal burning is a major source of heat-trapping carbon dioxide, a primary driver of climate change, and cutting down Appalachian forests for mountaintop mining releases more stored carbon to the atmosphere.

Researchers also have been studying the impact of mountaintop removal operations on the health of people living nearby.

Last August, the Trump administration, halted a health study on the impacts of mountaintop mining that was already underway by the National Academy of Sciences. A Department of Interior Inspector General's review found in June that the study had been canceled for no clear reason.

The study has not resumed, though, and the committee was disbanded earlier this year, Jennifer Walsh, spokeswoman for the National Academies of Sciences, Engineering and Medicine, told InsideClimate News on Tuesday.

"The National Academies still believe this is an important study of the potential health risks for people living near surface coal mine sites in Central Appalachia," she said.