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Before the arrival of Columbus in the Americas in 1492, the region had more than 60 million indigenous inhabitants in full swing.
A little more than a century later, this number had dropped by nearly 6 million.
Contact with Europe has brought not only war and famine, but also diseases such as smallpox that have decimated local populations.
Now, a new study published in the journal Opinion on Quaternary Science argues that these deaths occurred on such a large scale that they led to a "Little Ice Age": an era of global cooling between the 16th and the mid 19th century.
Although reporters report as if the argument was completely new, the basic concept dates back to 2003, when climate scientist William Ruddiman first proposed it. The new article is really a complete attempt to test an old idea. 2/15 https://t.co/YoNVRlRPuM
– Dagomar Degroot (@DagomarDegroot) January 31, 2019
Researchers from University College London found that after the rapid decline in the population, large tracts of vegetation and farmland had been abandoned.
Trees and flora that have repopulated unmanaged farmland have begun to absorb more carbon dioxide and keep it locked in the soil, eliminating an amount of greenhouse gases from the atmosphere such as Average temperature of the planet dropped by 0.15 degrees Celsius.
In general, experts consider the industrial revolution as the genesis of climate impacts caused by man. But this study shows that the effects may have started about 250 years ago.
"Humans have already changed the climate before the start of burning fossil fuels," Business Insider told the lead author of the study, Alexander Koch. "The burning of fossil fuel then went up the dial."
More than 50 million Aboriginal people died by 1600
Experts have long struggled to quantify the extent of the mbadacre of indigenous peoples of America in North, Central and South America. This is mainly due to the fact that no census data or population size records are available to determine the number of people who lived in these areas prior to 1492.
Researchers often rely on a combination of European witness accounts and documents relating to encomienda payments for tributes established during the colonial period.
But none of these measures is accurate – the former tends to overestimate the size of the population, as the first colonizers wanted to let donors know about European land recently discovered to European lenders.
The latter reflects a payment system put in place after many epidemics have already occurred, noted the authors of the new study.
The new study therefore proposes a different method: the researchers divided North and South America into 119 regions and reviewed all published estimates of pre-Columbian populations in each of them.
In doing so, the authors calculated that about 60.5 million people were living in the Americas before contact with Europe.
Once Koch and his colleagues gathered the before-and-after figures, the conclusion was critical. Between 1492 and 1600, 90% of the indigenous peoples of the Americas had died.
This means that about 55 million people have died because of the violence and new pathogens, such as smallpox, measles and influenza.
According to these new calculations, the number of deaths would represent about 10% of the total population of the planet at that time. It's more crowded than the modern populations of New York, London, Paris, Tokyo and Beijing combined.
The disappearance of so many people meant less farming
Using these population figures and an estimate of the amount of land used per capita, the study authors calculated that indigenous peoples were exploiting about 62 million hectares before contact with Europe.
This number has also decreased by about 90% to only 6 million hectares (23,000 square miles) by 1600.
Over time, trees and vegetation took over previously cultivated land and began to absorb more carbon dioxide from the atmosphere.
Carbon dioxide retains heat in the atmosphere of the planet (that is what human activity is now emitting on an unprecedented scale), but plants and trees absorb this gas in the part of photosynthesis.
For example, when land previously exploited in North and South America – equivalent to almost the size of France – has been reforested by trees and flora, carbon dioxide levels in the atmosphere have increased. decreases.
Antarctic ice cores dating from the late 1500s and 1600s confirm this decrease in carbon dioxide.
This drop in CO2 was enough to lower global temperatures by 0.15 degrees Celsius and contribute to the enigmatic trend of global cooling called the "Little Ice Age", during which glaciers developed.
Persistent doubts
"The researchers probably overestimate their case," said Live Science Joerg Schaefer of the Lamont-Doherty Earth Observatory of Columbia University.
"I am absolutely sure that this document does not explain the cause of the change of carbon dioxide and the change of temperature during this period."
Koch said some of the carbon dioxide decline could have been caused by other natural factors such as volcanic eruptions or changes in solar activity.
But he and his colleagues concluded that the death of 55 million Native Americans accounted for about 50% of the global reduction in atmospheric carbon dioxide.
"So you need natural and human forces to explain the decline," he said.
Koch said the results revisit our understanding of the duration since human activity influences the Earth's climate.
"The human actions of the time have caused a drop in atmospheric CO₂ that has cooled the planet long before human civilization cares about the idea of climate change," they wrote.
But they warned that if a similar reforestation event were to occur today, it would not do much to mitigate the current rate of global warming.
The decline in atmospheric carbon dioxide that occurred in the 1600s today accounts for only about three years of fossil fuel emissions, Koch said.
"There is no way to reduce fossil fuel emissions," he said, adding that reforestation and forest restoration are also crucial.
This article was originally published by Business Insider.
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