A hundred years ago an extended and permanent loss of forest occurred in Madagascar as a consequence of human activity.
Researchers from MIT and the University of Massachusetts at Amherst, have found that such a relevant transformation of the landscape could have occurred due to human settlers who set fire to the forests, in order to create new paths to herd cattle.
New findings could prove that our species had changed the planet’s physical environment long before the Industrial Era. Results come after researchers analyzed the composition of two stalagmites from a cave in northwestern Madagascar, which is a great indicator of the historical record of the environment above ground, say researchers in an MIT press release.
Results would appear to show that the composition of the selected stalagmites suddenly changed about a hundred years ago, from carbon isotope ratios of trees and shrubs to isotope ratios typical of grasslands. It could demonstrate that the environment changed from having forests to meadows.
This changes could have occurred due to climate change or a natural disaster. Nonetheless, researchers found that by that moment, oxygen isotope levels appeared to be similar in both stalagmites, suggesting that rainfall rates and climate were apparently stable.
“We went in expecting to just tell a climate change story, and were surprised to see a huge carbon isotope change in both stalagmites,” says David McGee, the Kerr-McGee Career Development Assistant Professor in the Department of Earth, Atmospheric and Planetary Sciences at MIT, in a press release published Wednesday.
Professor McGee explained that the speed at which the shift occurred and the fact that climate, in general, appeared to be in normal conditions could demonstrate that humans were involved. Results were published on February 15 in the journal Quaternary Science Reviews.
Unusual clues linked to grazing cattle
Stalagmites, which are fossilized groundwater deposits, are a rigorous recorder of climate and ecosystem changes, says professor McGee. It appears that it would be unusual for a forest to naturally turn into a grassland that quickly, he wrote in a press release.
The team of researchers has found evidence that approximately 3,000 years ago humans settled in Madagascar and then adopted an agrarian lifestyle. It has been proposed that they could have introduced cattle in the island located in the southeast coast of Africa about a hundred years ago, using slash and burn techniques to make way for the animals.
It seems interesting that such kind of environment changes occurred prior to the Industrial Era, McGee says. More investigations are going to be conducted by the team in order to understand when did the changes begin and how much time did it take for humans to transform the landscape.
Source: MIT Press Release