The disappearance of mammoths has cooled temperatures .

After the extinction of mammoth and other large herbivores, Earth's temperature dropped 7 ° C for almost a thousand years.Keywords: Mammoth, Warming.

12,800 years ago, the end of mammoths in America would have reduced emissions of methane.

There are nearly 15,000 years, large herbivores have begun to disappear from the American continent. Among the hundreds of extinct species, there were mammoths, ground sloths, camelids, horses, all much larger than they are now closely related. The reason for this loss remains controversial. Mammoths have been eliminated by man or by climatic changes after the fall of a meteorite? No conclusive evidence has yet been found. As a result, some scientists believe the phenomenon could be due to the combination of these two factors, or even several others remain unidentified.
The consequences of the disappearance of the megafauna herbivores on vegetation seem, however, now well documented. A recent study showed that pollen and spores deposited in bottom sediments of a lake in North America have changed beyond recognition during this period (Science, 19 November 2009). This week a new piece is made to that file to multiple branches. An advance team of U.S. researchers, in fact, the assumption that the extinction of all these large animals has helped to cool the global climate (Nature Geoscience, May 25, 2010).

"First disaster-related rights":
Rates of methane in Greenland ice cores and mathematical models to support the team led by Felisa Smith of the University of New Mexico, said the cooling of the Younger Dryas, 12,800 years ago, could s explained by the decrease in methane emissions produced previously by large herbivores. The average temperature was then dropped by about 7 ° C for nearly a thousand years. The hypothesis seems more probable that this period was characterized by a decrease in the methane into the atmosphere unparalleled in the past 500 000 years. A decrease whose origin is also still unexplained.
Researchers are cautious. "We calculated that the disappearance of the megafauna could explain 12.5% to 100% of the reduction of methane observed," they write. Although methane is a greenhouse gas emissions thirty times more potent than carbon dioxide (CO2), But emissions of this gas by the megafauna were insufficient unlikely to lead to a warming global climate, in spite of their body mass and abundance of which we know little.

Prime catastrophic event related to human:
Today's releases of methane from livestock are substantial. According to FAO, the digestive fermentation and manure account for 18% of total emissions of greenhouse gases globally. The researchers note that the models of IPCC (Intergovernmental Panel on Climate Change) leave out the production of wildlife.
"The extinction of the megafauna is the first catastrophic event related to human activity, the researchers conclude. Accordingly, the Anthropocene (when the man began to have major effects on the planet, Ed), should not begin with the industrial revolution in the nineteenthecentury, but with the massive migration of men in America, 13,400 years ago. "