Carbon sequestration estimation: quantifying what a plantation actually stores.

By measuring the trees rather than counting them. Sample plots are enumerated for species, height and girth; biomass is calculated using allometric equations published for those species or forest types; and biomass is converted to carbon and then to a carbon-dioxide equivalent using standard conversion factors. The sample design and equations should always be disclosed with the result.

Only as a projection, and it should be labelled as one. A freshly planted sapling stores very little carbon; the meaningful stock accumulates over years. Any figure quoted at planting is a modelled expectation based on assumed growth, and treating it as achieved sequestration is misleading.

They are estimates with real uncertainty, driven by the allometric equations chosen, the sample intensity and the growth assumptions. Reported honestly (with method, sample size and assumptions stated) they are perfectly adequate for corporate disclosure. Reported as a precise single number without basis, they invite challenge.

Carbon credit issuance is a separate process under a specific standard, with its own eligibility, additionality, baseline, verification and registry requirements. A sequestration estimate is useful supporting work but is not the same as certification under a carbon standard, and should not be presented as such.

Annually or at defined intervals, using the same sample plots, so a trend is built from consistent measurement. A single point estimate says what is stored now; a repeated series shows the rate of accumulation, which is what a sustainability report can actually track against.

Soil organic carbon is a genuine and often significant pool, particularly on a plot that has been amended with biomass and is accumulating litter. It requires its own soil sampling and analysis, and if it is to be included it should be measured and reported separately from the biomass estimate rather than folded in silently.