Did Reforestation in Colonial-Era Americas Cause a Drop in CO2?

Could reforestation efforts following the decimation of indigenous populations in the Americas during colonial times have caused a significant drop in CO2 levels? This question has sparked scientific debate for over three decades, triggered by the observation of a sharp decline in atmospheric CO2 around 1610 preserved in Antarctic ice.

This decline, unique in recent history, was attributed to the regrowth of forests in the Americas due to the population collapse caused by pandemics introduced by early European contact. This drop was so pronounced that it was even suggested as marking the start of the Anthropocene epoch.

However, recent studies have questioned this theory. Ice cores from Law Dome in East Antarctica showed that CO2 levels began to decline later than expected after European contact and plummeted too rapidly to be explained solely by reforestation rates. Another ice core from West Antarctica showed a more gradual decline, albeit with less detail.

To further investigate, Amy King and colleagues from the British Antarctic Survey drilled a new ice core at Skytrain Ice Rise in West Antarctica. This new core, filled with tiny air bubbles trapped as snow fell over millennia, aimed to shed light on the CO2 decline around 1610.

The team found that the Skytrain ice core did not show the sharp drop in CO2 levels seen in Law Dome. Instead, it revealed a gentler decline, matching the West Antarctic ice core.

The discrepancy suggests that the sharp drop seen in the Law Dome data might be an artifact. While the Skytrain data supports the idea that reforestation did occur, there’s limited evidence of extensive reforestation in the central Amazon during that time.

The study highlights the potential of reforestation as a means to reduce CO2, even though the historical evidence is still under scrutiny. It shows that despite the significant impact of European contact on indigenous populations, the reduction in CO2 levels was not as significant as previously thought.

Understanding the real impact of historical events like the colonial-era population collapse and reforestation on atmospheric CO2 levels could inform current efforts to combat climate change, particularly when discussing net-zero emissions.

In conclusion, while reforestation is a valuable tool for carbon sequestration, preserving existing forest and land carbon stocks and reducing emissions are paramount in addressing the climate crisis.