Biophysical Characterization (Polygon General)
Documentation for the Polygon General computation.
Overview
The Biophysical Characterization computation provides a biophysical and ecological characterization of a project area. It assembles contextual data on climate, biomass, terrain, and ecosystem classification that informs the literature review and preliminary carbon stock assessment required before detailed feasibility analysis begins. The computation has global coverage and no geographic restrictions.
Methodology
Biomass
Potential and current carbon storage are derived from Walker et al. (2022),¹ a global 500-meter resolution dataset estimating above- and below-ground carbon stocks and the theoretical maximum carbon storage under native vegetation cover. For each project area, the computation extracts:
- Mean potential carbon stock: the expected carbon storage under mature native vegetation, per the Walker dataset, used to bound growth model projections. This represents the fully restored ecosystem.
- Decile distribution of potential biomass: the distribution of Walker potential carbon values across pixels within the project area, providing spatial variability context
- Decile distribution of current biomass: the distribution of Walker current carbon values, reflecting the gap between existing and potential carbon storage
Climate
Mean annual precipitation (mm) and temperature (C) are derived from the WorldClim v2 global climate surfaces² at approximately 1 km resolution. Pixel-level distributions (histograms) are computed for both variables within the project boundary.
Terrain
Elevation, slope, and aspect are derived from the SRTM v4 global digital elevation model³ at 90-meter resolution. A per-pixel terrain summary table is produced for the project area.
Ecosystem Classification
Ecozones (IPCC): The project area is intersected with FAO Global Ecological Zones to identify the ecozones present. For each ecozone, IPCC biomass reference values at 10, 20, and 30 years post-restoration are reported, providing the basis for comparing project growth projections against published benchmarks.
Ecoregions (WWF): The project area is intersected with the WWF Terrestrial Ecoregions dataset from Olson et al. (2001). The area of overlap with each ecoregion is calculated, enabling assessment of biogeographic context and species composition expectations.
Köppen-Geiger Climate Classification: A spatial map of Köppen-Geiger climate zones is produced for the project area.
Outputs
The computation returns the following outputs:
| Output | Type | Description |
|---|---|---|
| Biophysical Context | Data table | Country, continent, mean potential biomass, biomass deciles, mean annual precipitation |
| IPCC Data by Ecozone | Table | IPCC biomass values at 10, 20, and 30 years for each ecozone within the project area |
| Ecoregion Table | Table | WWF ecoregion names and area overlap with the project boundary |
| Terrain Table | Table | Per-pixel elevation, slope, and aspect summary statistics |
| Köppen-Geiger Map | Map layer | Climate zone classification for the project area |
| WWF Ecoregions Map | Map layer | Ecoregion boundaries overlaid on the project area |
| Walker Potential Biomass Distribution | Histogram | Distribution of potential carbon storage values across project pixels (tCO₂e/ha) |
| Walker Current Biomass Distribution | Histogram | Distribution of current carbon storage values across project pixels (tCO₂e/ha) |
| Precipitation Distribution | Histogram | Distribution of mean annual precipitation across project pixels (mm) |
| Temperature Distribution | Histogram | Distribution of mean annual temperature across project pixels (°C) |
Footnotes
- Walker, W. S., et al. (2022). The global potential for increased storage of carbon on land. PNAS, 119(23).
- Fick, S. E., & Hijmans, R. J. (2017). WorldClim 2: new 1-km spatial resolution climate surfaces for global land areas. International Journal of Climatology, 37(12), 4302–4315.
- Jarvis, A., et al. (2008). Hole-filled SRTM for the globe, Version 4. CGIAR Consortium for Spatial Information.