Natural Risk (Internal)
Documentation for the Natural Risk computation.
Overview
The Natural Risk computation evaluates the exposure of a project area to natural hazards that could threaten the permanence of carbon stocks. It implements the risk scoring framework defined in Verra's Non-Permanence Risk Tool (NPRT), producing individual risk scores for each hazard category, an aggregate natural risk score, and a forward-looking assessment of climate-adjusted risk. These outputs are used to determine the buffer pool contribution required to account for non-permanence risk in ex-ante carbon projections.
Risk Scoring Framework
Each hazard is scored based on two dimensions:
- Likelihood: the expected frequency of the event, expressed as a return period or occurrence interval
- Significance: the estimated proportion of carbon stock that would be lost in the event
Individual risk scores are calculated by combining likelihood and significance according to the Verra NPRT scoring matrix, producing a score from 0 to 30. A mitigation factor may be applied to reduce the score where project design or management practices demonstrably reduce exposure.
The aggregate natural risk score is the combination of individual hazard scores, following the NPRT protocol.
Hazard Categories
The following natural risk categories are assessed:
Fire
Fire risk is assessed under multiple scenarios:
- With and without a buffer zone around the project boundary
- With and without adjacent agricultural land (which affects fire ignition probability)
Fire likelihood is derived from historical fire frequency data within and around the project area. Significance reflects the proportion of carbon stocks typically affected by fires of the assessed return period.
Drought
Drought risk is calculated from the project area's historical drought frequency using global drought monitoring datasets. Significance is based on estimated mortality and carbon stock loss under severe drought events.
Flood
Flood risk is assessed against a 100-year return period flood event. A spatial flood extent model is applied to the project area to estimate the proportion of land within the flood zone. A 100-year return period flood map is produced as a visual output.
Hurricane (Tropical Cyclone)
Hurricane risk is derived from the historical frequency of tropical cyclone tracks passing within a defined radius of the project area. Significance is based on the wind intensity and documented biomass impacts for the relevant biome.
Earthquake
Earthquake risk is evaluated using global seismic hazard datasets. Likelihood corresponds to ground-shaking intensity at the applicable return period; significance reflects documented carbon stock impacts from earthquake-induced landslides and canopy damage.
Volcano
Volcanic risk is assessed based on proximity to active volcanic centers and the historical frequency of eruptive events with documented vegetation impacts.
Landslide
Landslide risk is derived from a global landslide susceptibility model applied to the project area geometry, incorporating slope, lithology, and rainfall intensity inputs.
Pest and Disease
Pest and disease risk is assigned a fixed score reflecting the baseline exposure applicable to tropical and subtropical forest restoration projects (likelihood: 10–25 year recurrence; significance: less than 5% carbon stock loss). This score is treated as a constant across all project areas in the current implementation.
Outputs
| Output | Description |
|---|---|
| Individual Risk Scores | Per-hazard likelihood, significance, mitigation, and composite score for each category |
| Flood Map (100-Year Return Period) | Spatial map of estimated 100-year flood inundation extent within the project area |
| Fire Risk Scenarios | Risk scores and maps across fire scenario combinations |
| Aggregate Natural Risk Assessment | Combined NPRT risk score for the project area |
| Future Climate Risk Ratings | Forward-looking adjustment to aggregate risk under projected climate scenarios |
| Natural Risk Report | Structured markdown summary of all risk categories and scores |
Application to Carbon Projections
The aggregate natural risk score determines the buffer pool allocation applied to ex-ante carbon credit projections. A higher aggregate score results in a larger percentage of projected credits being placed in the non-permanence buffer pool and unavailable for issuance. The computation outputs are designed to feed directly into the buffer pool calculation step of the project feasibility workflow.
Limitations
Natural risk scores produced by this computation are derived from global and regional datasets and are intended for prefeasibility-stage analysis. Site-specific hazard assessments using locally collected data, hydrological models, or fire management plans may yield materially different scores. Final NPRT submissions to Verra require project-specific documentation that this computation does not replace.
Pest and disease risk is currently assigned a fixed score and does not vary by geography or species composition. Projects with specific known pest pressures should review this assumption with the Verra NPRT guidance before adopting the output score.
References
Verra. VCS Non-Permanence Risk Tool (NPRT), v4.0. Verra.