akar.earthBaseline scenario: Definition
What is a baseline scenario in carbon projects? How baselines are set for ARR and REDD+, why they decide credit volumes, and Indonesian pitfalls.
A baseline scenario is the most plausible description of what would happen to greenhouse gas emissions and removals in a project area without the carbon project. Credits are calculated as the difference between the baseline and the project scenario, minus leakage, uncertainty and buffer deductions.
Why it matters
The baseline is the single biggest lever on credit volume. Set it too high (too much assumed deforestation, too little natural regrowth) and the project is over-credited. Many of the integrity problems in older REDD+ projects trace back to inflated baselines. Rating agencies and the ICVCM scrutinise baseline methods closely.
How it is set
- Identify alternatives: list realistic land uses without the project, such as continued grazing, oil palm conversion or logging.
- Choose the most plausible: using legal, economic and historical evidence, often together with the additionality test.
- Quantify: estimate baseline carbon stock changes over the crediting period.
Modern methods reduce developer discretion. Verra’s VM0048 allocates a jurisdictional deforestation risk to REDD+ projects, and VM0047 measures ARR baselines with a dynamic performance benchmark from control plots. Baselines must be reassessed at intervals set by the standard. See baseline setting for detail.
Indonesia angle
In Indonesia, credible baselines must reflect the primary forest moratorium, spatial plans, concession status and historical drivers such as oil palm, pulpwood, mining and fire. Projecting conversion of land that is legally protected is hard to defend. For ARR on degraded land, the baseline is often continued grassland or shrub with slow natural regrowth, which control plots can now measure directly. Our page on the REDD+ baseline controversy explains what went wrong before.
Common mistakes
- Assuming worst-case deforestation without evidence of agents and drivers.
- Ignoring natural regeneration in ARR baselines.
- Not updating the baseline when policy or land status changes.
Related terms
See project scenario, additionality and leakage, or browse the carbon standards hub.
Frequently asked questions
What is the difference between a baseline and a project scenario?
The baseline scenario is what would happen without the project. The project scenario is what actually happens with it. Credits equal the difference, minus leakage and deductions.
Why are REDD+ baselines controversial?
Older project-level REDD+ baselines often projected high future deforestation that did not materialise, leading to over-crediting. Newer methodologies use jurisdictional data to set them.