Every restoration project sells a forecast before it sells a tonne. Investors, buyers and governments all want to know how much carbon the project will sequester over its lifetime, which is a question that must be answered years before the first measurement exists. Ex-ante modelling is how that answer is produced, and how defensible it is determines whether the project survives contact with reality.
What the Model Actually Chains Together
An ex-ante estimate is a sequence of conversions, each with its own assumptions and its own error.
| Step | Input | Principal uncertainty |
|---|---|---|
| Planting configuration | Species, density, spatial layout | Survival rate assumptions |
| Growth trajectory | Diameter and height over time by species | Growth model provenance |
| Biomass conversion | Allometric equation per species | Equation fit and calibration range |
| Wood density | Species-level density values | Database matching quality |
| Carbon fraction | Biomass to carbon | Relatively small and well constrained |
| Pool expansion | Below-ground, deadwood, litter | Ratio transferability |
The output looks like a single confident number. It is the product of six assumptions, and the weakest one dominates.
Survival Rate Is the Quiet Killer
Growth models get the attention. Survival assumptions do more damage.
A model assuming high survival across a full rotation, applied to a landscape where early mortality is substantial, overstates the result by a margin no allometric precision can recover. And unlike growth rates, survival is highly site specific, depending on soil, hydrology, browsing pressure, and maintenance capacity.
The defensible approach is to model survival conservatively, state the assumption explicitly, and run a sensitivity case showing what happens if it is worse than expected.
Why Conservative Modelling Is Commercially Better
An optimistic ex ante estimate sells more easily and creates a liability. Buyers who contract against a forecast and receive less do not simply accept the shortfall, because the project's credibility is spent, and the second sale is harder than the first.
A conservative estimate that the project then exceeds produces the opposite dynamic. That asymmetry is why experienced developers model low and report the sensitivity range rather than the single best case.
What Ex-Ante Cannot Do
It cannot substitute for measurement. An ex-ante estimate is a projection used for planning and contracting; credits issue against ex-post measurement of what actually happened.
Projects that treat the model as the answer rather than the plan are the ones surprised at first verification, which is when the sampling design, not the model, determines what can be claimed.
Turn uncertainty into a plan
Sampling design and growth assumptions decide how much measured carbon survives conservative deduction. TREEO Carbon Simulator models sequestration scenarios and biomass growth before the field season.
