When mandatory biodiversity net gain began for major developments in England on 12 February 2024, it was tempting to treat the cost consequence as an addition to landscaping. That approach risked missing the decisions that actually determine the expenditure.
The starting point was the ecological baseline and the proposed design. Until those were understood, a monetary allowance could give a misleading impression that the requirement had been resolved.
An estimator could still help before every detail was settled. Separate the cost of assessment and design from the proposed physical works. Ask whether the scheme expects to deliver its requirement on site, whether off-site provision may be needed, and which party carries the continuing management obligations. The ecological adviser should establish the biodiversity position; the estimate should make the corresponding scope visible.
- Ecology baseline
- Proposed design
- On-site delivery
- Off-site provision if needed
- Management obligations
Cost-planning questions, not a biodiversity metric or a legal compliance assessment.
Watch the interfaces
A habitat proposal may affect drainage, earthworks, planting and the usable development area. Pricing it as an isolated package can overlook costs already included elsewhere, or changes required in those other packages.
I would want the cost review to show a clear assumption for each interface. That makes subsequent design changes easier to value and prevents the same allowance appearing in both external works and a separate environmental line.
This is a review of the February 2024 introduction. Exemptions, application dates and subsequent changes need to be checked against the rules applicable to the actual project.