Native Americans Left Carbon Footprints

North America's Mid-Atlantic region was anything but a primeval wilderness when Europeans arrived, according to a new study of ancient fires and drought cycles.

Charcoal found in Buckeye Creek cave, W.Va., along with carbon and trace metals found in a stalagmite suggest that Native Americans burned the great forests regularly to grow the trees they preferred.

The evidence from the cave shows that before humans appeared in the area, drier times led to more fires, so droughts and fires tracked together, explains Greg Springer of Ohio University. That is, they do until about 2,000 years ago, when things got out of whack.

"Either there was a very extreme drying event or a change in vegetation," said Springer. "But there is nothing else that suggests change. That's when we saw that there was something unusual here."

That something was probably humans.

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In another nearby cave, archaeologists were excavating evidence of a 2,000-year-old human community in the area. These ancient people were probably tinkering with the forests with the most powerful tool they had: fire.

"The charcoal is what's really interesting," said Springer, the lead author on a paper on the matter in the latest issue of the journal The Holocene. "The greatest amount of charcoal was deposited at the same time that archeologists were saying that Native Americans were making use of the area. The second highest was when Europeans came into the area."

It turns out that Native Americans were, in fact, heavily managing the forests of the Mid-Atlantic right down to the species of trees and the sorts of animals that lived among them, says historical ecologist Marc Abrams of Penn State University. Abrams and his colleagues said as much in another paper in the same journal in 2008.

"(Springer's, et al.) conclusions are very much like what we see in our 2008 paper," said Abrams. The new geochemical work provides yet another line of evidence.

"For years people really thought that climate was the primary cause of vegetation changes," said Abrams. "We think that climate is important, but equally important is the role of human management of vegetation."

One of the signs of this has been staring people in the face for centuries: the oak, pine, chestnut, hickory and other species that dominate the Mid-Atlantic.

"We know that these species require disturbance," said Springer. "An important question is: 'Where did all these species come from?'"

The biggest disturber of forests are fires. According to Abrams, this begs the question: Where did all the fires come from? There's not enough lightning in that region to account for it, leaving just one other fire starter: humans.

And humans had very good reasons to be wielding fire.

"The species they were promoting are very important to their diet," Abrams said. "They were using active forest management -- silviculture -- to promote them. They were also attracting the animals they wanted to hunt."

As a result, these early Americans were also releasing carbon into the atmosphere -- a lot like their modern human counterparts.

"It changed the carbon cycle," said Springer. "Land clearing is a significant contributor. That did not begin at the Industrial Revolution."

That said, these pre-industrial carbon emissions are still dwarfed by emissions from fossil fuel burning today, Springer pointed out.

What the work shows, however, is that humans everywhere have been messing with the carbon cycle for a long time.