Possibly. Some scientists argue that so much farmland was abandoned after the Mongol invasions that regrowing forests pulled a noticeable amount of carbon from the air.
The idea is debated, not settled. When farms empty out, trees reclaim the fields and store carbon as they grow. Researchers have suggested the Mongol depopulation caused enough regrowth to leave a faint mark on atmospheric carbon, but the size of that effect is uncertain and other historical disasters complicate the picture.
