The BNG Spatial Risk Multiplier reduces the value of off-site biodiversity units when habitat compensation is located further from the biodiversity loss caused by a development. Under the current statutory biodiversity metric, area and hedgerow units within the same Local Planning Authority (LPA) or National Character Area (NCA) receive a multiplier of 1.0, neighbouring areas receive 0.75, and locations outside these areas receive 0.5.
For developers using off-site biodiversity units to achieve biodiversity net gain, location can therefore directly affect how many units are required and, consequently, project costs.
Understanding spatial risk early can help developers identify suitable units before finalising their BNG strategy and avoid sourcing units that lose a significant proportion of their value when entered into the statutory biodiversity metric.
What Is the BNG Spatial Risk Multiplier?
The BNG Spatial Risk Multiplier is a geographic scaling factor within the statutory biodiversity metric that reflects the relationship between biodiversity lost at a development site and habitat compensation delivered off-site.
The principle is straightforward: off-site gains closer to the impact site retain more of their biodiversity unit value. More distant gains receive a reduced value within the metric.
For area habitats and hedgerows, the current statutory metric applies the following spatial risk scores:
Within: 1.0
The off-site compensation is within the development site’s LPA boundary or National Character Area.
Neighbouring: 0.75
The compensation is outside the development site’s LPA or NCA but within a neighbouring LPA or NCA.
Outside: 0.5
The compensation is outside both the relevant and neighbouring LPA or NCA.
This means an off-site habitat does not necessarily have to be within the same local planning authority to receive the full 1.0 multiplier. Being within the same National Character Area can also satisfy the current “within” category for area and hedgerow habitats.
Why Does the Location of Off-Site BNG Units Matter?
Location matters because the statutory biodiversity metric incentivises developers to deliver biodiversity gains close to where biodiversity is being affected. More distant off-site gains are discounted, which can increase the quantity of units needed to meet the development’s BNG requirement.
This approach helps retain the ecological benefits of biodiversity enhancements closer to affected areas and local communities.
For example, imagine that a habitat bank creates 10 biodiversity units before spatial risk is applied.
If those units qualify for a 1.0 spatial risk multiplier, all 10 units retain their value for the development.
At 0.75, the same 10 units contribute 7.5 units.
At 0.5, they contribute only 5 units.
The underlying habitat has not changed. What changes is the value attributed to those off-site gains for that particular development through the biodiversity metric.
Government guidance confirms that biodiversity gains can be delivered anywhere in England, but the metric incentivises off-site gains closer to the development. It is therefore more accurate to say that developers are incentivised to source locally rather than saying off-site units must always come from the same LPA.
How Do LPA and National Character Area Boundaries Affect Spatial Risk?
For area habitats and hedgerows, the current metric considers both Local Planning Authority and National Character Area boundaries. An off-site site falling within either the same LPA or NCA as the impact site can receive the full 1.0 spatial risk score.
This can considerably broaden the search area available to a developer.
A habitat bank may sit outside the development site’s LPA but still share its National Character Area. In that situation, the units still qualify as “within” for spatial risk purposes.
Conversely, a site outside both the relevant LPA and NCA may fall into the neighbouring or outside categories, reducing the effective biodiversity value of its units for that development.
This is why searching for suitable off-site biodiversity units should consider both geographic frameworks rather than relying on the LPA boundary alone.
Does the Spatial Risk Multiplier Work Differently for Watercourses?
Yes. Watercourse habitats use catchment geography rather than LPA and National Character Area boundaries when determining spatial risk.
Under the current statutory biodiversity metric, watercourse compensation within the same waterbody catchment receives a spatial risk score of 1.0. Compensation outside that waterbody catchment but within the operational catchment receives 0.75, while compensation outside the operational catchment receives 0.5.
Different rules also apply to intertidal habitats, where Marine Plan Areas are used.
Developers should therefore establish which habitat unit type they need before searching the private market for off-site BNG units.
How Can Spatial Risk Increase the Number of BNG Units Required?
A spatial risk deduction can mean a developer needs to purchase a greater quantity of off-site units because each unit contributes less towards the development’s BNG requirement.
For example, suppose a development needs 6 effective off-site area habitat units.
If suitable units qualify for the 1.0 multiplier, 6 units provide the required value.
If otherwise suitable units receive a 0.75 multiplier, approximately 8 raw units would be needed to provide 6 effective units, subject to the wider metric calculation and trading rules.
If the units receive a 0.5 multiplier, approximately 12 raw units would be required to provide the same 6 effective units.
This simplified example demonstrates why the cheapest advertised unit price is not necessarily the cheapest solution for a development. Unit location and effective value need to be considered alongside price.
How Does Spatial Risk Affect Project Costs?
The Spatial Risk Multiplier can increase BNG costs because a lower multiplier may require the developer to secure more units to address the same biodiversity deficit.
Developers comparing off-site options should therefore consider the effective cost of satisfying their requirement rather than comparing biodiversity units purely on their headline price.
A lower-priced habitat bank further from the development could ultimately require more units. A more local habitat bank with a 1.0 multiplier could require fewer units and potentially provide a more efficient solution.
Other factors remain important too. Habitat type, trading rules, availability, and the specific unit deficit identified in the developer’s biodiversity metric all influence which off-site solution is appropriate.
This makes early assessment particularly valuable for financial planning.
What Is the Difference Between Spatial Risk and Strategic Significance?
Spatial risk and strategic significance are separate components of the biodiversity metric. Spatial risk considers the geographic relationship between the development’s biodiversity loss and off-site compensation, while strategic significance considers whether habitat creation or enhancement is located in an area identified as strategically important for nature recovery.
Local Nature Recovery Strategies identify priorities and potential measures for recovering or enhancing biodiversity within their strategy areas.
A habitat bank can therefore have advantages because of its strategic location, while spatial risk is considered separately within the metric.
Developers should not assume that a strategically significant habitat automatically avoids a spatial risk deduction. Both factors need to be correctly entered and assessed within the statutory biodiversity metric.
Do BNG Trading Rules Still Apply to Local Off-Site Units?
Yes. A favourable BNG Spatial Risk Multiplier does not override the statutory metric’s trading rules.
Trading rules help prevent losses of more valuable habitats from being compensated through inappropriate lower-distinctiveness habitats. Developers therefore need to source the right habitat types and biodiversity units, not simply the closest available units.
A habitat bank within the same LPA or National Character Area may receive a spatial risk score of 1.0 but still be unsuitable if its available units do not satisfy the development’s habitat requirements and trading rules.
The correct approach is therefore to consider habitat type, distinctiveness, unit availability, trading rules and spatial risk together.
When Should Developers Start Looking for Off-Site BNG Units?
Developers should investigate off-site options once their biodiversity metric is sufficiently developed to indicate the likely type and quantity of off-site units required.
Waiting until the final stages of the planning process can reduce the range of available units, particularly where specific habitat types are in demand.
Early market assessment allows developers to compare habitat banks across the relevant LPA and National Character Area, understand how the Spatial Risk Multiplier affects each option and obtain realistic cost information.
The metric may change as the development layout evolves. Updated calculations can therefore be used to obtain revised quotations and understand how design decisions affect the off-site requirement.
Where the right unit type is in short supply or favourable pricing is available, developers may also wish to explore whether units can be reserved or secured with a deposit.
How Does Spatial Risk Relate to the Biodiversity Gain Plan?
Where off-site units form part of a development’s BNG strategy, the final biodiversity metric calculation and off-site allocation feed into the Biodiversity Gain Plan.
Off-site gains must be registered on the Biodiversity Gain Sites Register and allocated to the relevant development before they can count towards its BNG requirement.
The local planning authority can then check that the off-site gains included within the Biodiversity Gain Plan correspond with the relevant registered allocation.
This makes selecting suitable off-site provision more than a procurement decision. The units need to work within the statutory biodiversity metric, satisfy applicable trading rules and be correctly registered and allocated.
How Do Statutory Biodiversity Credits Compare?
Statutory biodiversity credits are a last-resort option where a developer cannot achieve the required biodiversity net gain through on-site or off-site delivery.
A spatial risk adjustment also applies to statutory biodiversity credits. Each statutory credit provides 0.5 biodiversity units, meaning developers need to purchase two statutory credits for every one biodiversity unit required.
Credits are priced in tiers according to habitat type, with different prices applying depending on the habitat being compensated.
This can make statutory credits a significantly more expensive option than securing suitable off-site biodiversity units, reinforcing the importance of exploring appropriate private-market off-site solutions first.
How Civity Helps Developers Find Suitable Off-Site BNG Units
At Civity, we help developers interpret the completed biodiversity metric outputs supplied by their ecological team and identify the off-site biodiversity units required to satisfy their remaining BNG obligation.
We do not undertake the developer’s biodiversity metric calculation. Instead, we use the completed metric to understand the required habitat types and unit quantities before identifying suitable off-site options.
Location forms an important part of that process. We can consider the development site’s LPA and National Character Area alongside our available habitat bank units to understand how spatial risk may affect the value of different options.
We can then provide fast quotations for suitable off-site BNG units, helping developers compare the commercial implications of their available options.
Because development layouts and biodiversity metric calculations often evolve, Civity can also provide revised quotations as the unit requirement changes. This gives project teams greater visibility over potential BNG costs throughout the planning process.
Our work with habitat banks and landowners also gives us visibility across the supply side of the BNG market, helping connect appropriate habitat creation and enhancement opportunities with genuine developer demand.
Why Early Site Selection Matters for Off-Site BNG
The location of off-site biodiversity units can materially change their effective value within the statutory metric, making site selection an important part of a developer’s BNG strategy.
Under the current rules, area and hedgerow units within the same LPA or National Character Area can retain their full value through a 1.0 spatial risk multiplier. Neighbouring locations receive 0.75, while more distant provision receives 0.5.
However, proximity is only part of the decision. Suitable units must also meet the project’s habitat requirements and statutory trading rules.
By assessing spatial risk, habitat type, availability and price together, developers can make more informed decisions about their off-site BNG strategy and understand the likely cost before their Biodiversity Gain Plan is finalised.
For support identifying and pricing suitable off-site units, speak to Civity about your development’s BNG requirements.