War, plague no match for deforestation in driving CO2 buildup

Stanford, CA- Genghis Khan and his Mongol hordes had an impact on the global carbon cycle as big as today’s annual demand for gasoline. The Black Death, on the other hand, came and went too quickly for it to cause much of a blip in the global carbon budget. Dwarfing both of these events, however, has been the historical trend towards increasing deforestation, which over centuries has released vast amounts of carbon dioxide into the atmosphere, as crop and pasture lands expanded to feed growing human populations. Even Genghis Kahn couldn’t stop it for long.

‘It’s a common misconception that the human impact on climate began with the large-scale burning of coal and oil in the industrial era,’ says Julia Pongratz of the Carnegie Institution’s Department of Global Ecology, lead author of a new study on the impact of historical events on global climate published in the January 20, 2011, online issue of The Holocene. ‘Actually, humans started to influence the environment thousands of years ago by changing the vegetation cover of the Earth’s landscapes when we cleared forests for agriculture.’

Clearing forests releases carbon dioxide into the atmosphere when the trees and […]