Columbus’ Expeditions Triggered Plagues That Caused Carbon Dioxide Concentrations to Plummet Worldwide: Study

Columbus’ journey to the Americas was marred by brutal conquest and exploitation by European powers. However, the most devastating impact came not from physical violence, but the onslaught of diseases like smallpox and influenza, to which Indigenous populations had no immunity. Estimates suggest that between 80% and 95% of the Indigenous population perished within the first 150 years after European contact, tragically dwindling from thriving millions to less than 500 in mere decades.

In fact, so profound was the effect of such a drastic population decline, that it might even have affected global atmospheric compositions worldwide! This new bit of information comes from one of the most reliable sources of ancient history at our disposal: ice cores.

Ice cores, long cylinders of ice drilled from glaciers, act as natural archives of Earth's climate history. This is because these cores trap air bubbles over time, fossilising the atmospheric composition of the time period beneath layers of new ice. Scientists studying Antarctic ice cores from the 16th and 17th centuries noticed a peculiar anomaly — a significant drop in carbon dioxide levels from the Columbian era.

The missing carbon held the key. As Indigenous populations declined massively, vast swathes of cultivated land were abandoned. Researchers think that these were later captured by forests, absorbing vast amounts of carbon dioxide through photosynthesis. This terrestrial carbon uptake, estimated at around seven billion metric tons, significantly impacted the global atmosphere.

Plus, the research shed light on an ongoing ice core debate. There are two ice cores that have helped shape what we know about the atmosphere of the past two millennia: the Law Dome and the West Antarctic Ice Sheet (WAIS). While both revealed rapid decline in carbon dioxide concentrations during the 16th and 17th century, the former shows a much steeper plummet than the WAIS core.

“This corroborates modelled scenarios of large-scale reorganisation of land use in the Americas following New World-Old World contact," the paper explains.

The research on ice cores and the population collapse in the Americas highlights a previously unknown connection between human actions and climate change. While human activity today is a major driver of rising carbon dioxide levels, this historical event demonstrates a far-less common phenomenon — human-caused cooling. It serves as a stark reminder of the profound impact humans can have on the Earth's delicate climate balance.

The findings of this research have been published in Nature Communications and can be accessed here.

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