A carbon project does not have to measure every pool. Methodologies specify which are required and which are optional, and they permit optional pools to be excluded, but only in one direction, and only with justification.
The Five Pools
| Pool | Usually required? | Typically measured how |
|---|---|---|
| Above-ground biomass | Yes | Field plots, allometric conversion |
| Below-ground biomass | Usually | Root-to-shoot ratio from above-ground |
| Deadwood | Often optional | Transects or dedicated plots |
| Litter | Often optional | Small quadrats, dry mass |
| Soil organic carbon | Depends on ecosystem and activity | Cores at defined depth intervals |
Conservative Exclusion, Explained
The rule is asymmetric and frequently misunderstood. A pool may be excluded if excluding it understates the project's benefit, but never if it overstates it.
For a project that increases carbon stocks, excluding a pool that is also increasing is conservative: you are declining to claim credits you could have claimed. Excluding a pool that is decreasing is not conservative, because you are omitting a loss.
That distinction determines which exclusions a verifier accepts. A restoration project can often exclude litter conservatively; a project where site preparation disturbs soil generally cannot exclude soil.
The Pools Projects Wrongly Dismiss
Soil in peat and mangrove systems, where it routinely exceeds all living biomass combined. Treating it as minor because upland forest protocols treat it as minor is the single largest measurement error available in those ecosystems.
Deadwood after disturbance. A project area that has experienced fire or logging can hold a substantial deadwood pool that is actively decaying, which represents an emission rather than a stock.
Below-ground biomass in systems with unusual root architecture, where a generic root-to-shoot ratio derived from a different forest type imports error silently.
Document the Decision
Whichever pools are excluded, the justification belongs in the project design document, stated explicitly with the conservativeness argument. A verifier who has to infer why a pool is missing will assume the least favourable explanation, and price it accordingly.
Turn climate goals into a verified portfolio
TREEO connects the full carbon cycle, encompassing eligibility, simulation, real time monitoring, and registry ready reporting, while combining expert consulting with dMRV technology so the evidence exists before anyone asks for it.
