Science: Feb 12, 2012

Deforestation and climate change may seem like a familiar problem in today's ear. But a team of French scientists claim that even 3,000 years ago, people may have played a role in making the Central African rain forest in savannas we see today.

As the Bantu farmers expanded south and east to the rainforest in search of fertile agricultural land, savanna, they created a "corridor", which in turn helped to cut the forest and the lush landscape of drier grasslands according to a study published online this week in the journal Science.

Study leader Germain Bayon, geochemist at the French Research Institute for use on Sea, said he and his colleagues did not even think of people when they started studying sediment samples from the mouth of the Congo River. All they were trying to do was to match the rate of rainfall over thousands of years, with the degree of chemical weathering of minerals, how rocky material decomposes over time.

Soil can be divided into several natural reasons, the primary one is the rain. As it falls to Earth, atmospheric carbon dioxide reacts with minerals in the open stone trapped in the droplets and the soil. Potassium can be washed quickly, but the aluminum sticks around much longer. Thus, a number of chemical weathering is, aluminum is abundant of potassium.

Looking back over 20,000 years, their relationship seemed in sync with rainfall amounts of rain, and evidence of chemical weathering of rising or falling together.

But it's a decent relationship collapsed about 3000 years ago. Although the climate was drier in succession for some time the ratio of potassium aluminum in sediment increased significantly - and there was no plausible natural cause of the unexpected.

"When we first took a look at the results, we were overwhelmed," said Bayon.

Then the members of his research team to know Bantu migration, which began about this time, and an explanation began to fall into place.

Bantu people come to the rain forest areas and the tools that are made of iron smelting technology in the last chop down trees and clean up the area of vegetation and plants such as pearl millet, yams, according to a study. A number of archaeological sites and the presence of iron objects to back up this theory. Fewer trees to prevent erosion, the soil would have been much more susceptible to chemical weathering, even in the absence of heavy rainfall.

This man and his team said Bayon, might explain the strange increase in chemical weathering rates.

"It really makes a convincing case," said William Ruddiman, a geologist and climate scientist, University of Virginia, who did not participate in the study. "I do not see any alternative."

But another scientist outside archaeobotanist Katharina Neumann and Goethe University in Germany, said that the evidence does not add up. Pollen data indicate that the rainforest is not immediately segue into savanna if it is chopped off, but rather a secondary forest that pops up - so people did not make a dent in the woods as far as the authors argue.

And in any case, the area had grown progressively drier arrived long before the Bantu farmers, he added. Blaming people, such a drastic change in the environment is attractive "political dimension", but this oversimplifies the matter, said Neumann.

Science

Sunday, February 12, 2012

Makeup of rain forest may have been altered by farmers

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