The Last Frontier is vast, yet threadbare of roads. Settlements are motes on the terrain. There's so much space, so much of it inaccessible, that the US Forest Service—charged by Congress with keeping track of the nation's timber—readily admits that more than one-quarter of the state's forest has never been inventoried. But that's about to change.

The Forest Service has always counted trees, mostly so timber companies would know how many two-by-fours could be culled from a given forest. Climate change, though, has changed the agency's focus. Trees trap carbon, pulling it out of the atmosphere, and climatologists need to know exactly how much. With that data, they can build better models, and policymakers can prepare better tomorrows. So this summer, the Forest Service joined some earth science geeks from NASA to find a way to map more of Alaska's woods—and the carbon stored within.