Measuring the Forest's Carbon: The Technology Behind Tropical Carbon Accounting

Tropical forests store enormous quantities of carbon — but precisely how much carbon any particular forest area contains has historically been extremely difficult to measure. Traditional methods required teams of researchers to physically measure the diameter and height of every tree in sample plots, then apply allometric equations to estimate biomass and carbon content — a process that is accurate but extremely labour-intensive and spatially limited. A revolution in carbon measurement technology — combining satellite radar, airborne LiDAR, and machine learning — is enabling forest carbon to be measured at national and regional scales with increasing accuracy and decreasing cost.

NASA's GEDI Mission — Forest Height from Space

Forest carbon is primarily determined by forest height — taller, larger trees contain more biomass and store more carbon. NASA's GEDI (Global Ecosystem Dynamics Investigation) instrument, mounted on the International Space Station, uses laser pulses to measure forest height with extraordinary precision across the entire tropical belt. GEDI fires 25 billion laser shots per year, generating a global dataset of forest structure that enables carbon estimates at spatial scales previously impossible. Combined with synthetic aperture radar data from Sentinel-1 — which penetrates cloud cover and measures forest structure independently — GEDI data is enabling the first truly global, cloud-free measurements of forest carbon stocks.

LiDAR — The Gold Standard for Carbon Mapping

Airborne LiDAR (Light Detection and Ranging) — firing millions of laser pulses from an aircraft and measuring their return time to reconstruct a three-dimensional model of the forest — is the most accurate method currently available for measuring forest carbon. A single LiDAR flight can produce a detailed three-dimensional model of every tree in the surveyed area, from which biomass and carbon can be estimated with uncertainties of approximately 10-15%. The cost of LiDAR surveys has declined dramatically as the technology has matured, and national-scale LiDAR campaigns have been conducted in Colombia, Peru, and parts of the Amazon basin.