PA – Sand Excavators

Biodiversityvv0

Responsible:Niccolò Calandri

PA – Sand Excavators (pa_ns_sandexcavators)

Overview

The PA – Sand Excavators component measures the Pollinator Abundance (PA) specifically associated with pollinators that nest by digging in sandy, friable soils. 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).

Sand excavators include specialised solitary bee and wasp species that require specific sandy substrates to build their nesting galleries. These include Colletes spp. (plasterer bees), Dasypoda spp. (pantaloon bees) and some Andrena species specialised in sandy ground. They favour loose, well-drained sand, often on sun-exposed slopes, dunes, river banks and sand pits.

In the overall Nesting Sites (NS) formula, sand excavators carry weight 2, reflecting their ecological importance and the relatively specialised habitat they require.

Calculation Methodology

Calculated using the InVEST methodology (Sharp et al., 2020). For each land cover pixel, a nesting suitability value for sand 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: 2/13

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_sandexcavators`	—	[0, 8, 16, 24, 32, 40]	No

Level	Value	Interpretation
A (Excellent)	> 32	Broad availability of suitable sandy substrates
B (Good)	24 – 32	Good suitability; accessible sandy areas present
C (Moderate)	16 – 24	Average suitability; limited or fragmented sandy substrates
D (Poor)	8 – 16	Low availability; few natural sandy substrates
E (Critical)	0 – 8	Near absence of sandy substrates; unsuitable 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.
Westrich, P. (2019). Die Wildbienen Deutschlands. Ulmer Verlag.

Data Sources & References

Sources

WRD_INVST_99

Methodology

PA component for sand excavators. Calculated using InVEST methodology (Sharp et al., 2020). For each land cover pixel, a nesting suitability value for sand 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: 2/13. Scale: 0–1.