Habitat bank units or on site habitat creation

Choosing between habitat bank units and on site creation is a question about land, time and risk, and the metric answers part of it for you. Buying registered off site units gets the biodiversity gain condition discharged without giving up developable area, but the statutory metric applies a spatial risk reduction to units delivered away from the site, so you buy more units than you would create on site for the same uplift. Creating habitat inside the red line keeps the full value of every unit and the 30 year liability. Most schemes end up with a mixture, and the deciding factor is usually whether the layout has land that was never going to be built on anyway.

How each route delivers measurable units

Mandatory biodiversity net gain under the Environment Act 2021 inserted Schedule 7A into the Town and Country Planning Act 1990, applying a deemed planning condition that development must deliver at least a 10 per cent gain measured by the statutory biodiversity metric. It came in for major development on 12 February 2024 and for small sites on 2 April 2024.

On site delivery means habitat created or enhanced within the application boundary and counted in the post-development baseline of the metric. The uplift is calculated from the same habitat parcels the ecologist surveyed before the scheme was designed, so the gain depends on what was there to begin with. A site of arable land or amenity grassland has a low baseline and is comparatively easy to improve. A site with species-rich grassland or mature hedgerows starts high and is hard to better.

Off site delivery means allocating units from a separate parcel of land that has been entered on the biodiversity gain site register maintained by Natural England. The register records the habitat, the responsible party, the legal mechanism and the allocation to a specific development, and allocation is what allows the units to count towards your gain plan.

Statutory biodiversity credits sold by government sit behind both as a last resort. They are deliberately priced to be the least attractive option and they are only available once the on site and off site routes have been properly considered.

Registration and legal security

The two routes carry very different administrative loads at the point of decision.

On site habitat is secured through the planning permission itself: a landscape and ecological management plan, a condition requiring its implementation, and often a section 106 obligation carrying the 30 year management commitment and the monitoring fee that goes with it.

Off site habitat has to be legally secured before the biodiversity gain plan can be approved, by a conservation covenant with a designated responsible body or by a planning obligation, and it must be registered and allocated. If you are buying units from a habitat bank operator, the practical questions are whether the site is already registered, whether the habitat has already been created or is only planned, and whether the allocation can be made in time for your gain plan.

Timing catches people out. The gain plan is submitted after permission and before development begins, so a unit purchase that is agreed in principle but not registered and allocated will stop you starting on site.

Spatial risk and what it does to the sums

The metric does not treat a unit created 60 miles away as equal to one created on the site. It applies a spatial risk multiplier that steps down the value of off site units as the administrative and geographic separation from the development increases, so units in the same local planning authority area or National Character Area retain more of their value than units in a distant one.

The arithmetic consequence is simple. The further away the compensating habitat, the more units you buy for the same measured gain. The detail of how those bands work is set out in the spatial risk multipliers in the biodiversity metric, and it is the first thing to check when comparing quotes from two habitat banks at different distances, because a lower unit price can lose to a nearer site once the multiplier is applied.

A strategic significance multiplier sits alongside it, rewarding habitat created in a location identified in a local nature recovery strategy or equivalent plan. A habitat bank inside a mapped priority area can therefore beat a nearer one that is not.

Monitoring and management over 30 years

The 30 year commitment is the part developers underestimate, and it is where the two routes diverge most.

On site, somebody has to manage the habitat for three decades and report on it. On a housing scheme that usually means a management company funded by estate charges, with the ecological prescriptions written into a management plan and monitoring reports submitted to the council at defined intervals. The council will often require a monitoring fee to cover its own checking. If the habitat fails to reach the target condition, the obligation is yours to put right.

Off site, that liability transfers to the habitat bank operator, which is most of what you are paying for. The counterpart risk is counterparty risk: you are relying on an organisation to manage land for 30 years, so the covenant, the responsible body and the funding arrangement matter more than the unit price.

Where the habitat is created on site, the ecologist's baseline survey has to be done properly in the first place, which is why a Preliminary Ecological Appraisal at the right time of year is the foundation of the whole exercise rather than a box to tick.

Cost and what actually drives it

Unit prices are set by the market and by land values, so there is no national figure worth quoting. What is worth understanding is the structure of the cost.

For off site units the price reflects the land taken out of production, the cost of creating and establishing the habitat, 30 years of management, monitoring and reporting, the operator's risk margin, and the number of units you need after the spatial multiplier. For on site delivery the cost is the development value of the land given up, the capital cost of creation, the long term management funding, the monitoring and the risk of having to remediate failure.

That last item is the one to model honestly. A scheme that delivers its gain through a wildflower meadow on heavy clay with no watering regime has a real chance of failing its year five condition assessment.

Design consequences of delivering on site

Off site units leave the layout alone. On site delivery shapes it, and the schemes that do it well start the ecology early rather than retrofitting a gain calculation onto a finished masterplan.

What tends to work is using land that was already constrained: flood plain, easements, attenuation basins designed as wet habitat, buffers to watercourses and woodland, and open space that would have been mown amenity grass. Converting amenity grassland to species-rich grassland gives a meaningful uplift for very little lost value.

What tends not to work is counting narrow strips, highly trafficked margins and areas that will be mown by habit regardless of what the management plan says.

Mixing the two on one scheme

The hierarchy in the regime expects on site delivery to be considered first, and a gain plan that jumps straight to purchased units without explaining why on site creation was not possible invites a query from the authority.

A common and defensible position is to deliver what the layout can carry on site, including a genuine uplift on retained habitat, and to buy registered units for the shortfall. Set that out in the Biodiversity Net Gain Assessment with the metric calculations for both parts and the reasoning for the split.

Biodiversity net gain work falls squarely in the territory where a competent person is legally required: the Environment Act 2021 regime expects the statutory metric to be completed by someone competent to do it, and the biodiversity gain plan has to be approved by the local planning authority. An AI-assisted draft is a starting point for that ecologist, not a substitute for them.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.