Harvard Salata Institute

Harvard Voices on Climate Change: Measuring Forest-Based Carbon Emission Reductions

Harvard Voices on Climate Change hosted a deep dive into measuring forest‑based carbon emissions, highlighting nature‑based solutions such as deforestation avoidance and afforestation. The episode featured Harvard faculty Missy Hullbrook and Ben Taylor, who explained how forests act as a massive carbon reservoir—roughly a third of terrestrial land and comparable in stock to atmospheric carbon. The discussion underscored the difficulty of quantifying above‑ground carbon. Traditional methods rely on the U.S. Forest Service’s FIA plots, measuring tree diameters and applying allometric equations, yet these sparse samples struggle to scale across heterogeneous landscapes. Recent advances—Google’s Alpha Earth AI model integrating satellite, lidar, and ground data at 10‑meter resolution, and multi‑scale lidar surveys—promise more accurate, wall‑to‑wall biomass maps. Hullbrook illustrated the magnitude with a thought experiment: each square meter of Harvard Forest holds a 30 cm wood cube, growing an additional 8 cm cube annually. She also highlighted a bias in California’s carbon‑offset market, where projects cluster in high‑biomass areas to maximize credits. The Alpha Earth prototype and emerging lidar atlases, such as Sylvera’s biomass atlas, demonstrate how technology can fill data gaps and reduce verification uncertainty. Accurate, high‑resolution carbon accounting is essential for credible nature‑based credit markets, policy incentives, and global climate models. As uncertainties about the terrestrial sink’s true strength persist, improved measurement tools will shape investment decisions and the effectiveness of forest‑based mitigation strategies.