PA – Soil Excavators

Biodiversityv06.00 credits/per_km2

Responsible:Niccolò Calandri

PA – Soil Excavators (pa_ns_soilexcavators)

Overview

The PA – Soil Excavators component measures the Pollinator Abundance (PA) specifically associated with pollinators that nest by digging burrows in compacted soil. It is expressed on a normalised scale from 0 to 1 (dimensionless index) and is one of the sub-indicators of the InVEST Pollinator Model (Natural Capital Project).

Soil excavators constitute the largest group of European wild bees, including species such as Andrena spp. (mining bees), Halictus spp. and Lasioglossum spp. These pollinators dig tunnels and brood cells in compacted ground, preferring well-drained, clayey or loamy soils with sun exposure. Their abundance depends on the availability of undisturbed, unpaved and non-intensively tilled soils.

In the overall Nesting Sites (NS) formula, soil excavators carry weight 3 (the second highest after aerial cavities in vegetation with weight 5), reflecting their ecological importance for pollination services.

Calculation Methodology

Calculated using the InVEST methodology (Sharp et al., 2020). For each pixel of the land cover map, a nesting suitability value for soil excavators (0–1) is assigned based on the land use class. The PA value for this factor is obtained by integrating nesting suitability with accessible floral resources (FA), weighted by pollinator foraging distance.

Weight in overall NS calculation: 3/13

Scale: 0 (unsuitable habitat) – 1 (maximum suitability)

Data Sources

Code	Name	Provider	Resolution	Availability
`WRD_INVST_99`	InVEST Pollinator Model	Natural Capital Project, Stanford University	—	—

Quality Range and Levels

Indicator	Unit	Range	Inverted
`pa_ns_soilexcavators`	—	[0, 8, 16, 24, 32, 40]	No

Level	Value	Interpretation
A (Excellent)	> 32	Broad availability of suitable soils; undisturbed, well-drained ground
B (Good)	24 – 32	Good suitability; significant areas of natural soil
C (Moderate)	16 – 24	Average suitability; partially disturbed or limited soils
D (Poor)	8 – 16	Low availability; predominantly tilled or artificially compacted soils
E (Critical)	0 – 8	Near absence of suitable soils; sealed or degraded environments

References

Sharp, R. et al. (2020). InVEST User's Guide. The Natural Capital Project, Stanford University.
Potts, S.G. et al. (2010). "Global pollinator declines: trends, impacts and drivers". Trends in Ecology & Evolution, 25(6), 345–353.
Michener, C.D. (2007). The Bees of the World. 2nd ed. Johns Hopkins University Press.

Data Sources & References

Sources

WRD_INVST_99

Methodology

PA component for soil excavators. Calculated using InVEST methodology (Sharp et al., 2020). For each land cover pixel, a nesting suitability value for soil excavators (0–1) is assigned. The PA value integrates nesting suitability with accessible floral resources (FA), weighted by foraging distance. Weight in overall NS calculation: 3/13. Scale: 0–1.