An investigation finds that the killing of native people indirectly contributed to a colder period, causing the death of around 56 million people in 1600
European colonization of the Americas killed so many natives that it transformed the environment and caused the Earth's climate to cool down, according to new research.
Colonists killed large numbers of people in conflict and also spreading disease, reducing the indigenous population by 90% in the century after Christopher Columbus' initial trip to America and the Caribbean in 1492.
According to the researchers, this "large-scale depopulation" left vast tracts of agricultural land unattended, allowing the land to become overgrown with trees and other new vegetation.
The new study by scientists at University College London found that the new growth absorbed enough carbon dioxide from the atmosphere to actually cool the planet, with an average temperature drop of 0.15 ° C in the late 1500s. and early 1600s.
"The great death of the indigenous peoples of the Americas resulted in a human-driven global impact on the Earth system in the two centuries preceding the Industrial Revolution," wrote the UCL teams of Alexander Koch, Chris Brierley, Mark Maslin and Simon Lewis. .
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, snow storms were common in Portugal, and disrupted agriculture caused famines in several European countries. .
UCL researchers found that European colonization of the Americas indirectly contributed to this colder period by causing the deaths of some 56 million people in 1600. The study attributes the deaths to factors including introduced diseases such as smallpox and measles. as well as war and social collapse
The researchers then calculated the amount of land required by the indigenous people and then fell into disuse, finding that around 55 million hectares, an area roughly equivalent to France, were left vacant and reclaimed by carbon dioxide-absorbing vegetation.
The study outlines a past in which humans influenced the climate long before the industrial revolution, where the use of fossil fuels for the manufacture of goods, the generation of electricity and transportation has allowed tens of billions to be released. tons of carbon dioxide in the atmosphere.
Widespread deforestation for agriculture and urban development has also stimulated the release of greenhouse gases, causing the planet to warm by around 1 ° C over the last century. Scientists have warned that the world has just over a decade to slash emissions or face increasingly severe storms, droughts, heat waves, coastal flooding and food insecurity.
The revegetation of the Americas after the arrival of Europe helped decrease the global carbon content in the air, decreasing by about seven to 10 parts of carbon dioxide for every million air molecules in the atmosphere. This compares to the 3 ppm of carbon dioxide that humanity is adding to the atmosphere each year through the burning of fossil fuels.
“There is a lot of talk about 'negative emissions' coming up and using tree planting to remove carbon dioxide from the atmosphere and mitigate climate change,” study co-author Chris Brierley told the BBC.
“And what we see in this study is the scale of what is required, because the great death resulted in an area the size of France being reforested and that gave us only a few parts per million.
“This is useful; It shows us what reforestation can do. But at the same time, that kind of reduction is worth maybe just two years of fossil fuel emissions at the current rate. "
By Oliver Milman
Original article (in English)