Until the late 1950s, land clearing and cultivation emitted more greenhouse gases than fossil fuels. This was a direct legacy of the colonisation of North America. When the Europeans began settling across the continent in the 1800s, they began plowing the land in earnest. Within a few decades of intense tillage, they drove over 50 percent of the original organic matter from the soil. The productivity of the US Great Plains dropped by 71 percent within 28 years of the first European tillage. Source: [[Black Earth Wisdom]]