(BBC News) Colonization of the Americas at the end of the 15th Century killed so many people, it disturbed Earth's climate.
That's the conclusion of scientists from University College London, UK.
The team says the disruption that followed European settlement led to a huge swathe of abandoned agricultural land being reclaimed by fast-growing trees and other vegetation.
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This pulled down enough carbon dioxide (CO2) from the atmosphere to eventually chill the planet