Terra Preta
Amazon "Dark Earth"

Terra Preta soils were first reported by Portuguese settlers in the Amazon rainforest. After the Civil War, expatriate Southern plantation owners wrote of these black, productive soils.  Yet few scientists paid attention until 1966, when Dutch soil scientist Wim Sombroek published Amazon Soils to reveal these remarkably fertile soils weren't natural geological deposits, but man-made by indigenous tribes. Evidence was an abundance of broken pottery sherds in these black soils.

Another unusual feature of Terra Preta is charcoal.  Charred carbon is commonly 9-10% of these soils–often up to 20%. By comparison, USDA Certified Organic Standards require 4-5% organic carbon, by soil type. Typical US farmland is less than 2%.

Archaeological dating by radioactive carbon-13 isotopes found Terra Preta is centuries old, yet still remains fertile and productive. Scientific study traced these soils to the first made 6000 years ago in western Amazon foothills of Andes Mountains. In 2000 years, this soil-building practice spread east to the mouth of the Amazon. By another 2000 years – the time of Jesus Christ – enough land was converted from infertile clay to rich, dark Terra Preta to feed a population of millions.

The physical evidence of these agricultural soils triggered a revision of Amazon history. Archeologic digs at dozens of sites by international teams of scientists documented the new reality of dense populations millions in complex cities interlinked by broad pathways. This was reported by the first Spanish explorers to travel the Amazon River from source to mouth.  This fully flowered civilization then vanished in 70 years, leaving behind empty land of regenerating rainforest.

In 1992, Wim Sombroek suggested this char-in-soil strategy can remove CO2 from Earth's atmosphere to counteract climate change driven by accumulating greenhouse gases. In 2006, the first international conference on this soil carbon strategy was held in Australia.

In 2008, at a second international conference in Birmingham, England, the word "biochar" was created to describe charcoal made for this unusual, special purpose.

In August 2009, the first North American Biochar conference was held at Univ. of Colorado Boulder. What began sixmilennia ago in remote SouthAmerica is a worldwide movement to advance a crucial strategy for a human future.