Just in case you don't think humans don't have an impact on the environment, check out the story of Genghis Khan.
According to a new study reported here, Genghis Khan will probably go down as the greenest-ever invader. Julia Pongratz of the Carnegie Institution's Department of Global Ecology found that Genghis Khan killed so many people when he established his empire between the 13th and 14th centuries that huge swathes of cultivated land returned to forest. With the deaths of 40million people, large areas of cultivated land grew thick once again with trees, which absorb carbon dioxide from the atmosphere. According to the study, re-growth of forests during the Mongol invasion absorbed 700 million tons of carbon from the atmosphere, equaling the amount of carbon global society now produces annually from motor cars.
"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 Pongratz. "But during the longer-lasting ones like the Mongol invasion and the conquest of the Americas there was enough time for the forests to re-grow and absorb significant amounts of carbon."
Still, it's doubtful whether any of the Green parties around the world will adopt this as part of their election platforms. Not exactly a vote winner.