An Ecologist Maps Trees From 7,000 Feet

On the big island of Hawaii, a fungus called ceratocystis is murdering ‘ohii‘a trees—at least 1 million in the past eight years.

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Local forest experts had no idea how to contain the quick-killing pathogen, until an aerial survey from ecologist Greg Asner revealed a pattern they could distinctly see only from above. At the edge of Hawaii Volcanoes National Park, fences drew a sharp line between dead trees and healthy ones. The barriers kept out feral pigs, which, they realized, would gash the trunks with their tusks, enabling the infection. If the scientists could bar the ungulates, the ‘ÅŒhi‘as might survive. This type of insight from Asner, 51, has helped arboreal managers plot and maintain the health of forests for nearly a decade. “Doing good conservation requires knowing what you’ve got, where it is, and how it’s doing,” Asner says. His lab, aboard a twin-prop Dornier 228, produces maps that reveal the structure of the canopy, indicate how much carbon trees trap, and even estimate hydration to see how forests cope with drought. From his seat near the navigation console, 7,000 feet up, Asner directs the crew to capture swaths of land too large to take in from the ground and with greater de