Genghis Kahn: Tree-Hugging Slaughterer?

If environmentalists were really serious about cutting carbon, they'd just go out and slaughter about 40 million people. Or so one might deduce from a new study that finds Genghis Khan's murderous invasion actually sucked about 700 million tons of carbon from the atmosphere, reports Mother Nature Network. The trick? The aforementioned 40 million people who died in the Mongol invasion were no longer plowing fields or cutting down trees—leading to vast reforestation.

"We found that during the short events such as the Black Death and the Ming Dynasty collapse, the forest re-growth wasn't enough to overcome the emissions from decaying material in the soil," explains the lead researcher. "But during the longer-lasting ones like the Mongol invasion ... there was enough time for the forests to re-grow and absorb significant amounts of carbon." (More Genghis Khan stories.)