European colonizers killed so many Native Americans that it changed the global climate

European settlers killed 56 million indigenous people over about 100 years in South, Central and North America, causing large swaths of farmland to be abandoned and reforested, researchers at University College London, or UCL, estimate. The increase in trees and vegetation across an area the size of France resulted in a massive decrease in carbon dioxide (CO2) in the atmosphere, according to the study. 

University College London researchers estimate that settlers killed 56 million indigenous people, causing farmland to be reforested. That increase in vegetation resulted in a massive decrease in carbon dioxide in the atmosphere.

READ: European slaughter of Native Americans changed the climate, study says - CNN