How a Scientist Mapped the Chemistry of the Entire Peruvian Amazon by Plane

Greg Asner used a golden sensor to measure the density of the leaves, their levels of essential nutrients like nitrogen, water, calcium, phosphorus, and their levels of two defensive chemicals—lignins and polyphenols. And by using machine-learning algorithms to interpret these seven traits, he has shown that the Amazon can be divided into 36 distinctive types of forest, which fall into six major groups.