A biodiversity offset only delivers a genuine net gain when the offset ratio and additionality standard are both strict enough that the conservation truly wouldn't have happened otherwise.
net_gain = offset_habitat*ratio*additionality - development_loss
- Development sites — sites where habitat loss requires a biodiversity offset.
- Offset network connectivity — how directly each development site is matched to a verified offset site.
- Offset ratio — how much replacement habitat is required per unit of habitat destroyed.
- Additionality strictness — how rigorously the scheme verifies the offset wouldn't have happened anyway.
Offset schemes with weak additionality checks have been shown to count conservation that was already planned, delivering zero real net gain — this model makes that failure mode visible.