Europeans invading the Americas caused so much death and destruction that they warped the planet’s climate.
Colonizers killed off 56 million people across North, Central and South America within 140 years of arriving on the continent, triggering a global cooldown.
That’s because large swathes of farmland abandoned in the wake of the devastation quickly reforested, sucking up greenhouse gases from the atmosphere, according to a new study.
Carbon levels changed enough to cool the Earth by 1610, just over a century after Columbus arrived in 1492.
“CO2 and climate had been relatively stable until this point,” said study author and University College London scientist professor Mark Maslin.
“So, this is the first major change we see in the Earth’s greenhouse gases.”
The drop in temperature during this period is known as the “Little Ice Age,” a time when the River Thames in London would regularly freeze over. The findings were published in Quaternary Science Reviews.
Across the European continent, the old and young died in their homes while livestock perished in fields frozen over by the cold during some of the worst winters in history.
Prior to their study, scientists thought the drop in global temperatures was triggered by natural causes.
To test this theory, scientists mixed together archaeological evidence, historical records and examinations of ancient carbon found in Antarctic ice.
They showed that reforestation that occurred as Europeans swept through the Americas was in fact responsible.
According to the study, 56 million hectares rapidly returned to jungle in just a few decades.
It sucked up carbon dioxide from the atmosphere, which normally acts as a barrier that traps heat from the sun.
“For once, we’ve been able to balance all the boxes and realize that the only way the Little Ice Age was so intense is … because of the genocide of millions of people,” Maslin told CNN.
Settlers killed off huge swathes of people during several decades of bitter conflict.
Millions also lost their lives to European diseases that natives had no natural immunity to.