You might never know it, but the seemingly quiet Harvard Forest in Massachusetts is actually hard at work. Like other forests, it's busy doing some serious global housekeeping, which is being monitored by scientists at Harvard University. "There's this enormous sucking sound, metaphorically speaking, that is happening across the New England landscape and the eastern US. It's the carbon being brought down out of the atmosphere, into our forests, which is reducing the amount that is up in the atmosphere," says David Foster, who is director of the Harvard Forest, which stretches for 3,000 acres, near Petersham, Mass., about 60 miles west of Boston. With support from the National Science Foundation, Foster and other researchers here study forest ecology. "We're trying to understand what shaped the land, where the landscape is going, and what's going to be the fate of the land in the eastern United States," he explains. That research includes determining how the forest responds to carbon dioxide in the atmosphere.