Humans Set Madagascar's Forests on Fire 1000 Years Ago

First Posted: Feb 19, 2016 09:00 AM EST

Humans had a larger impact on the past of Madagascar than you might think. Scientists have found that 5,000 years ago, humans set the region on fire.

There's no question that humans have had a dramatic impact on the planet's physical environment, particularly over the last few centuries with the rise of modern industry, transportation and infrastructure. With that said, humans have been transforming the landscape since before the start of the Industrial Era. Now, scientists have discovered evidence of widespread and permanent loss of forests in Madagascar that occurred 1,000 years ago.

In this latest study, the researchers examined two stalagmites from a cave in northwestern Madagascar. Stalagmites form from water that percolates from the surface, through the soil, and into a cave. Their composition actually serves as a historical record of the environment above ground.

The researchers found that about 1,000 years ago, both stalagmites' calcium carbon composition shifted suddenly and completely from carbon isotope ratios typical of trees and shrubs to those more consistent with grassland within just 100 years.

Was this transformation triggered by climate change? That might not be the case. Around the same time, the scientists found that oxygen isotope levels remained the same, indicating that rainfall rates remained consistent.

So what happened instead? Humans settled on Madagascar about 3,000 years ago and later adopted a more agrarian lifestyle, introducing cattle slightly before 1,000 years ago. It's possible that humans used slash and burn techniques to create pastureland about 1,000 years ago, destroying forests and causing the massive change in the ecosystem.

The findings reveal the massive impact that humans can have on an area. Not only that, but it shows humans have an impact not just today, but also a thousand years ago.

The findings are published in the journal Quaternary Science Reviews.

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