The Nesting Sites index (NS) measures the presence and suitability of areas where pollinators can establish their nests, expressed on a normalised scale from 0 to 1 (dimensionless index). It is one of the three core indicators of the InVEST Pollinator Model (Natural Capital Project), together with Nectar Potential (NP) and Pollinator Abundance (PA).
Nesting sites are a critical resource for the pollinator life cycle: without suitable nesting areas, even landscapes rich in floral resources (high NP) cannot sustain stable populations. Availability of nesting sites depends on soil structure, vegetation cover and the presence of suitable substrates for the different reproductive strategies of pollinators. High NS values indicate landscapes with adequate habitat structures for pollinator reproduction, with positive effects on Pollinator Abundance (PA) and related ecosystem services (Potts et al., 2010).
NS integrates with NP and PA in the InVEST model: areas with good nesting sites (high NS) but scarce nectar resources (low NP) will not reach optimal PA levels; the optimal combination of NS and NP determines maximum pollinator abundance.
The Nesting Sites index is calculated using the InVEST methodology (Sharp et al., 2020) as a weighted average of six nesting factors, each associated with a reproductive strategy of pollinator species:
| Factor | Description | Weight |
|---|---|---|
| Ground excavators | Pollinators that nest by digging burrows in compacted soil | 3 |
| Sand excavators | Pollinators that nest in sandy, friable soils | 2 |
| Underground cavities | Pollinators that occupy natural or pre-existing underground cavities | 1 |
| Aerial cavities (wetland) | Pollinators nesting in cavities of marsh and wetland vegetation | 1 |
| Aerial cavities (vegetation) | Pollinators nesting in hollow stems, branches and aerial plant structures | 5 |
| Coastal areas | Pollinators nesting in coastal and riparian substrates | 1 |
The calculation formula is:
NS = (3·NS_soil + 2·NS_sand + 1·NS_underground + 1·NS_wetland + 5·NS_vegetation + 1·NS_coastal) / 13
where each component is calculated as the specific suitability for that nesting strategy, based on land cover and habitat characteristics.
Scale: 0 (no suitable sites) – 1 (maximum nesting suitability)
| Code | Name | Provider | Resolution | Availability |
|---|---|---|---|---|
WRD_INVST_99 | InVEST Pollinator Model | Natural Capital Project, Stanford University | — | — |
| Indicator | Unit | Range | Inverted |
|---|---|---|---|
ns | — | [0, 10, 20, 30, 40, 50] | No |
Inverted = No: a higher value indicates greater nesting suitability and better conditions for pollinators.
| Level | NS | Interpretation |
|---|---|---|
| A (Excellent) | > 40 | Broad availability of nesting sites; structurally rich habitat |
| B (Good) | 30 – 40 | Good suitability; landscape with diverse nesting habitats |
| C (Moderate) | 20 – 30 | Average suitability; some suitable substrates present but limited |
| D (Poor) | 10 – 20 | Low availability; simplified habitats with few suitable sites |
| E (Critical) | 0 – 10 | Near absence of suitable sites; degraded or sealed environments |
| Indicator | Code | Description | Relationship with NS |
|---|---|---|---|
| Nectar Potential | np | Nectar produced in the area (kg/ha/yr) | NP and NS jointly determine PA |
| Nesting Sites | ns | Suitability of areas for nesting (0–1) | — |
| Pollinator Abundance | pa | Habitat suitability index for pollinators (0–1) | PA depends on NP and NS |
ns
Calculated using the InVEST methodology (Sharp et al., 2020) as a weighted average of six nesting factors: ground excavators (weight 3), sand excavators (2), underground cavities (1), aerial cavities wetland (1), aerial cavities vegetation (5), coastal areas (1). Formula: NS = (3·NS_soil + 2·NS_sand + 1·NS_underground + 1·NS_wetland + 5·NS_vegetation + 1·NS_coastal) / 13. Scale: 0–1. Requires Land Cover and Element-e processing (NS module).