Farmers May Have Kicked Off Local Climate Change 3,500 Years Ago
Humans may have been causing climate change for much longer than we’ve been burning fossil fuels. In fact, the agrarian revolution may have started human-induced climate changes long before the industrial revolution began to sully the skies. How? Through the clearing of forests, which still remains the second-largest source of greenhouse gas emissions from human activity.
Sediment cores from the mouth of the Congo River—the deepest river in the world—suggest that humans may have played a significant role in changing the landscapes of Central Africa. That river curves through the world’s second-biggest lingering tropical forest, but it and its tributaries also flow through the savannas so prized by modern-day safaris.
Scientists had previously thought that a climate shift from warm and humid to seasonally cooler and drier had helped create those savannas, which covered even more of Central Africa in the past. But the 40,000-year-old record preserved in the sediment cores tells a different story. Roughly 3,500 years ago the Congo River suddenly began dumping a lot more muck without any appreciable increase in rainfall to explain such weathering. One plausible explanation is the simultaneous arrival of the so-called Bantu people, who brought farming into the region.