Some years ago, scientists exploring the deep recesses of the
Amazon basin discovered something strange. Under the surface
layer of decayed leaves and wood on the jungle floor was a deep
layer of black earth they called Terra Preta. It was the
remnants of an agriculture practiced by pre-Columbian Amazonians
who had roasted wood in an almost airless fire, smoldering until
the wood turned not into normal charcoal, but into a roasted
black earth that they buried to help fertilize their fields.
Soils in the Amazon basin are notoriously poor, but the addition
of the charcoal, now called biochar, rendered them marvelously
fertile. By the time the first Spanish conquistadores arrived,
their scouts reported the existence of great walled cities
housing many thousands of people. These reports were regarded as
fiction until the first decade of the 21st Century, when
scientists discovered the remains of those cities and their
agriculture. Those ancient people grew their food on huge swaths
of soil improved with biochar,