Deep in the rain forest, a network of microphones listens for the chainsaws of
illegal loggers.Since rangers can only be in so many places at once, this new technology can alert them to where deforestation is taking place.
While other monitoring also happens—software can analyze satellite images to detect deforestation, for example—it usually comes too late, after trees have already been cut down and hauled away. Illegal logging now happens at a vast scale; tropical deforestation now emits more CO2 than the entire European Union.