SOS Forests

Did Native Americans Impact the Climate?

Researchers at Ohio University have found evidence that pre-Columbian Indians did a lot of landscape burning. The evidence includes carbon deposited in a stalagmite found in a cave near Buckeye Creek.

Study finds new evidence of pre-colonial land use patterns

Ohio University, Research Communications, Friday April 16, 2010 [here]

ATHENS, Ohio (April 15, 2010) – A new study led by Ohio University scientists suggests that early Native Americans left a bigger carbon footprint than previously thought, providing more evidence that humans impacted global climate long before the modern industrial era.

Chemical analysis of a stalagmite found in the mountainous Buckeye Creek basin of West Virginia suggests that native people contributed a significant level of greenhouse gases to the atmosphere through land use practices. …

One stalagmite does not make the case, but there is plenty of other evidence that human beings have been burning landscapes since we evolved from proto-humans. The Holocene is recent. The record of hominids and fire goes back 2 million years. We also know why our ancestors did all that burning:

The early Native Americans burned trees to actively manage the forests to yield the nuts and fruit that were a large part of their diets.

“They had achieved a pretty sophisticated level of living that I don’t think people have fully appreciated,” said Gregory Springer, an associate professor of geological sciences at Ohio University and lead author of the study, which was published a recent issue of the journal The Holocene. “They were very advanced, and they knew how to get the most out of the forests and landscapes they lived in. This was all across North America, not just a few locations.” …

This evidence suggests that Native Americans significantly altered the local ecosystem by clearing and burning forests, probably to make fields and enhance the growth of nut trees, Springer said.

This picture conflicts with the popular notion that early Native Americans had little impact on North American landscapes. …

The “popular notion” is changing, or has changed. We have called recognition of historical human influences on the environment a “paradigm shift”, so we are equally guilty of broad brush characterizations of the mass consciousness. To be completely fair, quite a few people have known all along that human beings burned landscapes just about everywhere on the planet. The shift from “quite a few” to “general knowledge” is difficult to track, however.

One question that remains controversial is whether setting continents afire every year altered the climate:

“Long before we were burning fossil fuels, we were already pumping greenhouse gasses into the atmosphere. It wasn’t at the same level as today, but it sets the stage,” Springer said.

This long-ago land clearing would have impacted global climate, Springer added. Ongoing clearing and burning of the Amazon rainforest, for example, is one of the world’s largest sources of greenhouse gas emissions. Prehistoric burning by Native Americans was less intense, but a non-trivial source of greenhouse gases to the atmosphere, he said.

Now hold on there, Dr. Springer. It can be established that fossil fuel burning is more intense today, but landscape burning is much less intense than in prior centuries and millennia. Prehistoric burning by Native Americans covered vastly more acres per year than are currently burned. The amount of sequestered carbon on the landscape is much greater today than it was 1,000 years ago in both the Americas.

Be that as it may, no causal connection has been established between atmospheric carbon and climate. There appears to be no correlation — as atmospheric carbon has increased during over the last 100 years, global temperatures have fluctuated up and down. Correlation is NOT the same as causation, but if there is no correlation then logically there can be no causation.

It is good to see that recognition of historical human influences is on the increase in the mass consciousness. We should not leap to conclusions, however, about the role of humanity in global warming.