akar.earthControl plot: Definition
What is a control plot in carbon MRV? How control plots are chosen and monitored to measure baselines under VM0047 ARR, with tips for Indonesia.
A control plot is an area outside a carbon project, chosen to resemble project land, where no project activity takes place, so that its change over time shows what would have happened without the project. Control plots turn the baseline from a projection into an observation.
Why it matters
The baseline is the biggest lever on credit volume, and it is a counterfactual that cannot be observed directly in the project area. Control plots provide the closest real-world proxy. Verra’s VM0047 area-based approach uses them to build a dynamic performance benchmark, which sets ARR baselines and tests additionality. Well-chosen controls make credits more credible; poorly chosen ones can either inflate or wipe out credits.
How control plots are selected and monitored
- Matching: statistical matching on covariates such as initial vegetation, rainfall, soil, slope, elevation and access.
- Independence: controls must be far enough from project activity that planting, protection or leakage does not affect them.
- Number: enough controls to represent project conditions with acceptable uncertainty.
- Monitoring: remote sensing time series, with field checks where useful.
Our pages on the VM0047 area-based approach and plot sampling design cover the details.
Indonesia angle
Indonesian landscapes are fragmented: smallholder farms, plantations, villages and forest remnants sit side by side. Finding matched controls not influenced by other planting programmes, oil palm expansion or fire can be hard. Cloud cover limits optical imagery, so radar or multi-sensor composites may be needed. Field teams can verify control conditions while running project plot campaigns. See ground truth vs satellite for why field data still matters.
Common mistakes
- Choosing controls by convenience, not matching.
- Placing controls where other restoration programmes later operate.
- Treating controls as fixed and not replacing ones that become invalid.
Related terms
See dynamic performance benchmark, stratification and remote sensing, or explore the dMRV hub.
Frequently asked questions
How are control plots chosen?
They are matched to project plots on factors that drive vegetation change, such as initial land cover, climate, soils, slope, elevation and distance to roads or settlements, and must be outside project influence.
Do control plots need field visits?
Under VM0047's area-based approach, control plots are monitored mainly by remote sensing, but field checks help confirm land cover and spot disturbances.