As European colonizers spread throughout North America and wiped out Native Americans, they unwittingly changed the world’s climate.
That’s according to a study published in the journal Quaternary Science Reviews, which posits that the genocide of millions of Native Americans helped cause a dip in global temperatures.
The study says global cooling happened during a period known as the “Little Ice Age,” which The Encyclopedia of Global Environmental Change says took place between the 16th and 19th centuries.
After European colonizers showed up in North America at the end of the 15th century, they exposed Native Americans to diseases like smallpox, which they had no immunity to, the study says.
An estimated 90 percent of Native Americans perished by the start of the 17th century, many from disease, the study says. That is “around 10% of the global population at the time,” the study’s authors wrote in a piece for The Conversation.
The genocide also left their agricultural areas without anyone to watch over them — allowing plants to regrow and absorb CO₂. Chris Bierley, one of the study’s authors, told the BBC that “an area the size of France” regrew its vegetation after the Native American genocide.
With a drop in carbon emissions from the “Great Dying” of Native Americans, the world’s global temperature dropped by about 0.15 degrees Celsius, according to the study.
And what effect did that reduction in CO₂ and temperature have across the world?
“During this period, severe winters and cold summers caused famines and rebellions from Europe to Japan,” the study’s authors wrote in The Conversation.
Ed Hawkins, who teaches climate science at Reading University in the United Kingdom, told the BBC that this study ties into others about the Little Ice Age while offering new information.
“Scientists understand that the so-called Little Ice Age was caused by several factors: a drop in atmospheric carbon dioxide levels, a series of large volcanic eruptions, changes in land use and a temporary decline in solar activity,” he told the BBC.
“This new study demonstrates that the drop in CO₂ is itself partly due the settlement of the Americas and resulting collapse of the indigenous population, allowing regrowth of natural vegetation,” he continued, according to the BBC. “It demonstrates that human activities affected the climate well before the industrial revolution began.”
But don’t expect this study to provide a blueprint for how we can avoid climate change in the future, the study’s authors wrote.
“Such a dramatic event would not contribute much to easing the rate of modern global warming, however,” they wrote in The Conversation. “The unprecedented reforestation event in the Americas led to a reduction of 5 parts per million CO₂ from the atmosphere – only about three years’ worth of fossil fuel emissions today.”