Mapping Rain Forests to Fight Climate Change

6 December 2014

Almost a century ago, Russian botanist N.I. Vavilov was traveling the world in search of new species when he identified why equatorial rain forests are so critical to the Earth’s future: They’re the source-pool for 90 percent of the planet’s biodiversity. Rain forests have been the focus of global conservation efforts ever since. Today, as climate negotiators convene for the United Nation’s Climate Summit 2014 in Lima, Peru—a country that is dead-center in that genetically rich belt of land around the equator, now known as the Vavilov Centers—another scientist-adventurer is on the verge of again revolutionizing the world’s approach to rain-forest conservation. This time, the goal is to use the rain forests to help save the planet, by turning them into what is essentially a storage container (or ”sink”) for the world’s most prominent greenhouse gas, carbon dioxide.

Greg Asner, an environmental science professor at Stanford University and director of the Carnegie Institution for Science’s Airborne Observatory, spends about half of every year in the jungle or flying above it in his juiced-up Dornier 228 prop plane. From up in the air, Asner’s invention, the Airborne Taxonomic Mapping System, beams a pair of laser signals down at 500,000 pulses per second to measure the carbon embedded in the sinews of every tree, root and plant in the forest. When the signal bounces back, an on-board spectrometer reads it and spits out color-coded results: Red signifies high levels of carbon concentration, signs of a healthy forest; browns signal a forest degraded through logging, mining or agricultural clearing; deep blues emanate largely from urban areas like Lima, signifying the absence of trees.

Asner came to the climate conference to present his unprecedented accomplishment: the first high-resolution carbon map of an entire country. He documented the carbon sequestered in every one of Peru’s 128 million hectares (about 320 million acres), over half of which is forested.

Asner’s invention has technological dazzle, but its significance lies in how it addresses one of the fundamental challenges that have long bedeviled climate negotiators. Deforestation, according to the U.N., accounts for about 15 percent of all greenhouse gases—more than car, air and ship travel combined. That’s because about half of the mass in trees is made up of carbon. Burn a tree or cut down a forest, and that carbon combines with oxygen to make carbon dioxide, the most prevalent of the five greenhouse gases. The world has a profound interest in keeping those trees growing; they’re the best natural system we have for sucking up carbon dioxide direct from the atmosphere rather than contributing to the greenhouse gas load.

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