PA – Aerial Cavities (Vegetation)

Biodiversityv06.00 credits/per_km2

Responsible:Niccolò Calandri

PA – Aerial Cavities Vegetation (pa_ns_aboveground_cavities_vegetated)

Overview

The PA – Aerial Cavities (Vegetation) component measures the Pollinator Abundance (PA) specifically associated with pollinators that nest in hollow stems, dead branches, tree holes and aerial plant structures. It is expressed on a normalised scale from 0 to 1 and is the most important sub-indicator of the InVEST Pollinator Model.

This group includes a wide range of solitary bees and bumblebees: Osmia spp. (mason bees, using wood cavities and hollow stems), Megachile spp. (leafcutter bees), Xylocopa spp. (carpenter bees, boring into dead wood) and many bumblebees occupying tree holes. Hedgerows, dead-standing trees, uncut margins and forest edges are key habitats for these species.

In the overall Nesting Sites (NS) formula, aerial cavities in vegetation carry the maximum weight of 5 (out of 13 total), reflecting the crucial importance of structured vegetation for solitary bee and bumblebee nesting.

Calculation Methodology

Calculated using the InVEST methodology (Sharp et al., 2020). For each land cover pixel, a suitability value for vegetation aerial cavities (0–1) is assigned. The PA value integrates nesting suitability with accessible floral resources (FA), weighted by foraging distance.

Weight in overall NS calculation: 5/13 (highest)

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

Level	Value	Interpretation
A (Excellent)	> 32	Structurally rich vegetation: mature hedgerows, dead-standing trees, forest edges
B (Good)	24 – 32	Good availability; hedgerows and cavity-bearing trees present
C (Moderate)	16 – 24	Average availability; partially managed or young vegetation
D (Poor)	8 – 16	Low availability; heavily managed or monoculture vegetation
E (Critical)	0 – 8	Near absence of structured vegetation; open or artificial 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.
Dicks, L.V. et al. (2015). "How much flower-rich habitat is enough for wild pollinators?". Journal of Applied Ecology, 52(4), 1067–1075.

Data Sources & References

Sources

WRD_INVST_99

Methodology

PA component for aerial cavities in vegetation. Calculated using InVEST methodology (Sharp et al., 2020). For each land cover pixel, a suitability value for vegetation aerial cavities (0–1) is assigned. Weight in overall NS calculation: 5/13 (highest). Scale: 0–1.