05.02.2019, 19:5306.02.2019, 13:09
Man is changing the climate. Although this finding is not undisputed, it is shared by the clear majority of climatologists. The anthropogenic change in the climate is one of the reasons why some scientists are even talking about a new geological era, the Anthropocene.
However, when it comes to man-made climatic phenomena, the focus is rarely on processes that took place before the start of the industrial revolution. This does not apply to a study dealing with the effects of the European colonization of America – long before the first steam engines – on the global climate. The researchers at University College London, who published their findings in the “Quaternary Science Reviews”, come to the surprising conclusion that the so-called “Little Ice Age” is one of the unforeseeable consequences of this world-historical process.
This cooling of the climate, which began in the 15th century and lasted into the early 19th century, followed the Medieval Warm Period and was caused by increased volcanic activity and, to a lesser extent, reduced solar radiation. The global temperature dropped by about 0.8°C during the Little Ice Age; in some European regions it was even lower by up to 2°C. This led to crop failures in agriculture and, as a result, to more frequent famines.
In addition to the factors mentioned that caused this cooling, the study mentioned should also be responsible for the mass extinction that began with the beginning of the European colonization of the American continent. The massive population decline in North America, but above all in Central and South America, meant that huge areas were no longer used for agriculture and were therefore again overgrown by forest. The newly formed forests bound so much of the greenhouse gas CO at high speed2 from the air that the temperature dropped worldwide.
In fact, after the arrival of the Europeans in 1492, a terrible bloodletting ensued among the native population. Estimates of the population of the American double continent at the end of the 15th century differ from each other, but the authors of the study assume a population of around 60 million, which corresponded to around ten percent of the world population at the time. About half of them lived in Central America, a quarter in the Inca Empire.
The conquerors from Europe persecuted and enslaved the indigenous population. Image: public domain
A hundred years later, the indigenous population had shrunk to just 4 to 5 million. Around 1500 there were still 22 million inhabitants in Mexico, around 1600 there were just under 1 million.
This, in absolute numbers, the greatest demographic catastrophe of mankind was caused by wars, but also by the – partly organized – persecution and enslavement of the locals. By far the most important cause, however, were diseases such as measles or smallpox, which were brought in by the Europeans and against which the indigenous population had hardly any defenses.
Diseases – here smallpox – killed millions after the arrival of Europeans in America. Image: Shutterstock
A population decline of this magnitude inevitably had consequences for the agricultural land cultivated in America. Around 55 million hectares of cultivated land – an area the size of France – now lay fallow and was reclaimed by nature. The millions of trees and other plants now overgrowing the fields drew so much CO2 from the atmosphere that, according to the study, this will result in a significant decrease in global CO2-levels effected. This in turn led to an average cooling of 0.15°C in the late 16th and early 17th centuries.
Evidence that between the two processes – i.e. the decline in land use and CO2-Decrease – the researchers found that there could be a connection in a completely different place: in Antarctica. Ice drilling there shows that in the 16th century an abnormal decrease in CO suddenly occurred2-Salary in the atmosphere.
At the same time, studies on the American continent also point to differences in the coal and pollen deposits – presumably fewer areas were set on fire so that they could be used for agriculture again. So nature had a free rein there.
The map shows pre-Columbian land use and Central and South American areas affected by plagues around 1600. Map: Sciencedirect.com/Alexander Koch
Ed Hawkins, a climatologist at Reading University who was not involved in the study, told the BBC scientists believe the Little Ice Age was caused by a variety of factors. In addition to volcanic activity and the temporary reduction in solar radiation, he also mentions changes in land use and the decrease in CO2– Salary in the atmosphere. The new study shows that the CO2-Decline caused in part by the discovery of the Americas and the collapse of the indigenous population.
The authors of the study point out that their research shows that human influence on the climate began before the industrial revolution. Global warming, which is troubling us today, is based on the opposite effect: Burning fossil fuels and burning forests releases more CO2 into the atmosphere than is rebound by the growth of vegetation.
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