Credit: University of Maine Photosynthesis is the oldest carbon-capture technology on Earth. For eons, plants have pulled carbon dioxide from the atmosphere and locked carbon—the building block of life on our planet—into their bodies and roots. In young forests, the widespread consensus is that this process rapidly pulls, or sequesters, carbon from the atmosphere. As forests mature, more trees start to die, releasing the carbon they captured in their wake. Carbon sequestration, the thinking goes, slowly stalls and old forests eventually release roughly as much carbon into the air as they capture. Thirty years of measurements taken by University of Maine scientists at a remote 550-acre forest challenge this idea. At Howland Research Forest, located about 30 miles north of Orono, Maine, in the towns of Edinburg and Howland, 98-foot towers rise above the spruce and hemlock canopy.…