akar.earthAbove-ground biomass: Definition
What is above-ground biomass (AGB)? Definition, how it is measured with plots, allometry and remote sensing, and why it drives forest carbon credits.
Above-ground biomass (AGB) is the dry weight of all living vegetation above the soil, including stems, branches, bark, leaves and seeds. In most forests it is the largest and best-measured carbon pool, so it drives most forest carbon credit calculations.
Why it matters
ARR projects earn credits mostly from the growth of AGB, and REDD+ projects earn them by avoiding its loss. Methodologies treat it as a mandatory pool. Errors in AGB estimates translate almost one-to-one into errors in credit volume.
How it is measured
- Field plots: teams measure DBH, height and species for every tree in sample plots.
- Allometry: an allometric equation converts each tree’s size and wood density to biomass.
- Scaling: plot biomass per hectare is extrapolated to the project area by stratum, with sampling uncertainty reported.
- Carbon conversion: biomass × carbon fraction (often 0.47) × 44/12 gives tonnes of CO2.
Remote sensing extends plot data across large areas. Lidar, GEDI canopy height, radar and optical imagery are calibrated against plots. Our guide to remote sensing biomass explains the trade-offs, and CO2 from biomass walks through the arithmetic.
Indonesia angle
Indonesian forests span a very wide biomass range: tall lowland dipterocarp forest in Kalimantan and Papua holds far more AGB per hectare than degraded secondary forest or young smallholder agroforestry. Peat swamp and mangrove forests need forest-type-specific equations. Cloud cover limits optical imagery, which raises the value of radar and of good ground plots.
Common mistakes
- Using a biomass map as a substitute for field data rather than as a stratification aid.
- Mixing up AGB (dry matter) with carbon or CO2 units.
- Ignoring below-ground biomass, which adds a meaningful share on top of AGB.
- Measuring only large trees and missing saplings that dominate young ARR plantings.
Related terms
Above-ground biomass is one of five IPCC carbon pools, with below-ground biomass, dead wood, litter and soil organic carbon. Our ARR hub explains how these pools build up a project’s removal estimate over time.
Frequently asked questions
How is above-ground biomass converted to carbon?
Multiply dry biomass by a carbon fraction, commonly the IPCC default of 0.47 for tropical wood, then multiply carbon by 44/12 to express it as CO2.
Can satellites measure above-ground biomass directly?
Not directly. Satellites measure proxies such as canopy height or radar backscatter, which are calibrated against field plot biomass.