By Jon Turner, Forum contributor

Can humans really affect Earth’s climate? Christopher Columbus did. 

Vermont’s second official Indigenous People’s Day is a good time to take another look at a historical villain who may have inadvertently chilled our planet by a tenth of a degree. 

The national Columbus Day holiday is under increasing fire lately amid a growing recognition of the Genoese navigator’s crimes against indigenous peoples, the Taino and Arawak. These crimes included torture, child rape, slavery, murder, and the commission of an “American Holocaust” that reduced the population of Hispaniola to a bare handful of survivors.  

As our historical understanding of Columbus has grown, so has our understanding of Pre-Columbian peoples and their relationship with Earth’s climate. Increasingly, researchers debunked the colonial myth of unsophisticated “savages” inhabiting a trackless wilderness prior to European colonization. Estimates of pre-colonial indigenous population size have increased steadily over the past century, from about 40 million to more than 120 million people, including estimates of the colonizers’ environmental impacts.  

Columbus may not have technically “discovered” America—it would be racist to say a lost white guy “discovered” an already-prosperous hub of international trade and the people who had already been living there for centuries—but some of his microscopic passengers did discover a whole new world upon his arrival. 

Diseases introduced by Columbus and his European successors included the bubonic plague, measles, smallpox, mumps, chickenpox, influenza, cholera, diphtheria, typhus, malaria, leprosy, and yellow fever—a Pandora’s box of maladies to ravage the indigenous cities of America.  

These infections led to “virgin-soil epidemics” among peoples with no developed resistance, eventually sowing economic chaos and political collapse. As late as 1616, a plague swept the coast of New England, killing nine of ten people who contracted the plague.

The horror must have been indescribable. Eurasian diseases combined with European colonists and genocidaires, migration and resource conflict, to claim the lives of some 55 million indigenous Americans by the year 1600—a count comparable to the Black Death in Europe. 

But how does the depopulation of an entire hemisphere affect the climate? Evidence suggests that these deaths led to widespread reforestation of the Americas and a major drop in atmospheric carbon dioxide. In many parts of the Americas, farmers engaged in slash-and-burn agriculture, clearing fields from forest tracts. One study suggests post-Columbian depopulation transformed Central America from “a net source of CO2 to the atmosphere before the arrival of Columbus to a net carbon sink for several centuries following the Columbian encounter.”  

The abandonment and reforestation of some 56 million hectares of farmland likely accounts for more than half of the reduction in atmospheric carbon dioxide between 1520 and 1610. This came at the height of the Little Ice Age, when an “So extreme, very unseasonable, quite frostie.” winter drove English colonists from New England for a full decade.  

Why is this research important? It suggests that human activity caused major changes to our planet’s climate well before the Industrial Revolution. And while technology may help us to mitigate the ways in which we’re harming our environment, truly sustainable development for Earth’s 7.5 billion residents may require measures more dramatic than we’ve ever contemplated. 

On the positive side, the next time someone tries to tell you that human activity cannot affect the climate, you can tell them: That ship sailed in 1492.