> For the complete documentation index, see [llms.txt](https://aetlas.gitbook.io/aetlas/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://aetlas.gitbook.io/aetlas/for-project-developers/references-and-other-guidance/additional-principles-for-forestation-and-agroforestry-projects/carbon-accounting-and-mrv.md).

# Carbon accounting and MRV

PROJECT DEVELOPERS MUST 

* Justify the models and assumptions used to quantify carbon accumulation in the above-ground biomass, below-ground biomass and (when the pool is included) organic soil pools. -
* Specify key assumptions that materially-affect modeled carbon accumulation rates, such as the geographic and environmental variables, species-specific allometric models, and expected seedling survival rates. 
* Use statistically valid sampling methods and best-available models (for example, species-specific and region-specific allometric equations) for quantifying aboveground carbon. 
* Use data from in-situ sampling or conservative root:shoot ratios (that is, use smaller ratios to mitigate uncertainty) to quantify changes in below-ground carbon, where this pool is included. 
* Measure and monitor changes in soil carbon when claiming removals in soils, using the criteria for high-quality soil carbon. 

PROJECT DEVELOPERS SHOULD 

* Use ground inventories whenever feasible to validate remotely sensed measurements of above-ground biomass changes. 
* Use site-specific data and/or collect data needed to parametrize models used to estimate biomass changes (such as species-specific allometries and wood densities measurements). 
* If soil carbon is not directly measured, establish projects on lands where the net impact of forestation or agroforestry on soil carbon is expected to be positive (e.g., degraded lands). 
* Quantify any GHG fluxes associated with site preparation including removal of existing vegetation. If GHG fluxes are determined to be de minimis, the project developer should articulate why. 
* Include a life cycle assessment of harvested products for agroforestry and plantation projects. 
* Account for applicable and appreciable indirect climate impacts. For example, projects occurring in high altitude/latitude areas should account for changes in albedo due to establishment of tree cover.