January 25, 2016

Massive Native American depopulation in 17th century was rapid, caused forest fires

In a new study published by the Proceedings of the National Academy of Sciences journal, researchers found Native Americans living in the Southwest continued to thrive for nearly a century after their initial contact with Europeans. However, when native population in the Southwest began to drop, it did so at a fast pace.

The study was based on laser-based mapping of almost 20 Native American village sites.

"In the Southwest, first contact between native people and Europeans occurred in 1539," study author Matt Liebmann, an anthropologist from Harvard University, said in a statement. "We found that disease didn't really start to take effect until after 1620, but we then see a very rapid depopulation from 1620 to 1680. (The death rate) was staggeringly high -- about 87 percent of the Native population died in that short period.


Discovery of the Mississippi by William H. Powell (1823–1879) is a Romantic depiction of de Soto seeing the Mississippi River for the first time. It hangs in the United States Capitol rotunda. (Credit: Wikipedia)

"Think about what that would mean if you have a room full of people and nine out of 10 die," he added. "Think of what that means for their social structure, if they're losing the people who know the traditional medicine, their social and religious leaders, think of the huge impact it would have on their culture and history."

But wait, there's more!

The study team noted that forest fires began to escalate as native populations declined. This is because indigenous people in the Southwest cleared the land for farming and settlements. When the population dropped, forests expanded and fires became more prevalent, the study team claimed.

The study’s conclusion reinforces the theory that we have entered a new geological era – the Anthropocene. Supporters of this theory point to ice core data that shows a drop in global carbon dioxide levels at the same time native populations across the Americas were in rapid decline.

"One of the 'Early Anthropocene' theories suggests that because Native Americans were being removed from the landscape on a massive scale, especially in the Amazon, they were no longer burning the forest for agriculture, and as the forest re-grew it sequestered carbon," Liebmann said. "The argument hinges on the notion that the depopulation of the Americas was so extreme that it left its mark on the atmosphere and climate at global scales.

"Our data speaks to a period a little bit later than the dates of low CO2 from the ice cores, but depopulation in the Southwest could have intensified that dip," he added.

A not-so-simple massive depopulation

In addition to mapping the sizes of various native villages, the study team also looked at tree rings from the area to determine the general age of the surrounding forest.

"When we looked at the patterns of fires in the tree rings, we could see that up until about 1620, fires were small and sporadic," Liebmann said. "Native American fields were acting as literal fire breaks. But as the forest started re-growing, much more widespread fires occurred. That continued until almost exactly 1900, when a combination of increased livestock grazing and a change in federal forest management policies began to suppress all fires."

He said his team’s conclusion reveals the complexities of native population decline in the New World.

"Our findings support the notion that there was a massive depopulation, but it's not quite as simple as many people have thought before," Liebmann said. "This research also speaks to...current debates in the American West about how we should manage fire risk. What our study shows is that forest fires were being managed by Native people living in dense concentrations on the landscape -- not unlike the situation today in many parts of the Southwest. So there may be some lessons here for contemporary fire management."


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