Genghis Khan might have been the greenest invader of all time – his bloody conquests killed so many people, that in their path, huge swathes of cultivated land returned to forest, eliminating a huge amount of carbon from the atmosphere.
While the Mongol ruler wasn’t even thinking about it, he was causing the first man-made global cooling.
‘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,’ said Julia Pongratz, who headed the research by the Carnegie Institution’s Department of Global Ecology. ‘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,’ she explained.
Now, before you get into some very wrong conclusion – this is in no way connected to current climate change, and no one is suggesting fighting climate change through war and conquest – that’s nonsense. What this study does do is provide insight into how long events must be to create durable shifts in the planet’s climate.
‘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,’ explained Pongratz. ‘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.’
It also reveals new information about the carbon cycle, and how we are affecting it, potentially yielding valuable information for policy makers.
‘Based on the knowledge we have gained from the past, we are now in a position to make land-use decisions that will diminish our impact on climate and the carbon cycle,’ she concluded.