In fact, the Mongol Emperor’s environmental contribution helped eliminate 700 million tons of carbon! He also let forests regrow where they had been chopped down to make room for towns and farm land. This was especially significant when you consider the large size of the mongol empire.
This wasn’t because Kahn was a tree hugger. In fact, this wasn’t even deliberate. The reason there was room for the forests was because he had the towns and villages in their place burned down and helped reduce the carbon output by (ahem) driving down the number of people.
It wasn’t just the size of the empire that made this significant. The fact that the mongol empire lasted so long meant that massive areas of green space were able to regrow where towns and farms had been destroyed. Just don't let Greenpeace know that this happened or they might get any ideas on using the same tactics (kidding, kidding)