The four bands
- Low (1.0): arable field margin, scrub, modified grassland.
- Medium (0.667): native hedgerow, semi-improved neutral grassland.
- High (0.333): lowland mixed deciduous woodland, lowland meadow, chalk grassland.
- Very High (0.1): lowland fen, blanket bog, coastal saltmarsh, priority watercourse.
The full table is in the JP039 technical annex.[S1]
Why borderline schemes flip off-site
A scheme requiring 4 BU of high-distinctiveness compensation at Very High difficulty would need to deliver 40 BU of raw score on-site to satisfy the requirement after the 0.1 multiplier; on practically any developable parcel that is infeasible. The arithmetic alone forces off-site supply for high-difficulty habitats.
Worst-case compounding
Very High difficulty + 30-year target condition + outside-NCA spatial risk + low strategic significance: 0.1 x 0.355 x 0.5 x 1.0 = 0.018. The post-development habitat returns under 2% of its raw distinctiveness score; the unit deficit is severe and the rational route is in-LPA off-site purchase.