A milpa is a field, usually but not always recently cleared, in which farmers plant a dozen crops at once, including maize, avocados, multiple varieties of squash and bean, melon, tomatoes, chilis, sweet potato, jicama (a tuber), amaranth (a grain-like plant), and mucuna (a tropical legume). The term means “maize field,” but refers to something considerably more complex. “Indian farmers grow maize in what is called a milpa. More important, the very existence of so much healthy forest after twelve thousand years of use by large populations suggests that whatever Indians did before swidden must have been ecologically more sustainable.”ġ491: New Revelations of the Americas Before Columbus (Large cattle ranches are the major offenders in the Amazon, but small-scale farmers are responsible for up to a third of the clearing.) Fortunately, it is a relatively new practice, which means it has not yet had much time to cause damage. At the same time, it pours huge amounts of carbon dioxide into the air, a factor in global warming. The burning sends up in smoke most of the nutrients in the vegetation-almost all of the nitrogen and half the phosphorus and potassium. Although swidden does permit the forest to regrow, it is wildly inefficient and environmentally unsound. Slash-and-burn cultivation has become one of the driving forces behind the loss of tropical forest. “In the Amazon, the turn to swidden was unfortunate.

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