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On 16 April 2026, the Government published its response to the May 2025 consultation on improving the implementation of biodiversity net gain (BNG) for minor, medium and brownfield development (see here). Although last year's consultation focused mainly on minor and medium schemes, several of the confirmed changes will impact major development, particularly reforms to the spatial risk multiplier (SRM) and the treatment of open mosaic habitat (OMH) on brownfield land. On 16 April, the government also published a new consultation on a targeted BNG exemption for residential brownfield development (see here). This consultation closes soon, on 10 June 2026. What do developers need to know when deciding whether to respond?
May 2025 consultation: key proposals for major development
The May 2025 consultation proposed a range of measures aimed at easing the BNG burden. We considered the potential impact of these on major development in section 4 of our May/June 2025 newsletter (see here). We now know that the Government intends to bring forward the following changes within a phased timetable over the second half of 2026.
1. SRM reform: Local Nature Recovery Strategy (LNRS) boundaries
This is likely to be welcome news for developers. Using Local Nature Recovery Strategy (LNRS) areas rather than LPA or National Character Area boundaries for the purposes of the SRM (as currently required) should widen the pool of nearby off-site habitat providers, potentially lowering the cost of securing off-site units. It should also make the system more resilient to local government reorganisation.
The Government aims to introduce this change through secondary legislation later in 2026, subject to parliamentary scheduling. Transitional arrangements will apply for projects already in progress, which are to be confirmed. Existing approaches will remain in place for intertidal habitats and the watercourse module.
2. Brownfield development and OMH
Defra has confirmed that it will work with industry to improve guidance within the BNG metric to make OMH and other urban habitats easier to identify. It also intends to allow the use of proxy habitats as an alternative to OMH compensation, and is considering a new medium-distinctiveness habitat category similar to “sparsely vegetated urban land”.
These changes respond to a long-standing viability concern for brownfield development. A new urban habitat category could also address a gap in the current metric, which has made baselining some brownfield sites difficult and costly. However, the detailed definitions and condition criteria are still to be worked through. Until the statutory metric is updated later in 2026, the current OMH compensation requirements will remain in force.
3. New targeted exemptions
Three new exemptions will be introduced through secondary legislation.
- The most practically relevant for many developers may be the exemption for temporary planning permissions of five years or less. This could be useful where a wholly temporary development, such as a meanwhile use, requires standalone permission, provided that no on-site priority habitats are affected. The Government intends to introduce this in a first wave of secondary legislation before 31 July 2026, subject to parliamentary scheduling.
- A second exemption will apply to development that is wholly or primarily for the purpose of conserving or enhancing biodiversity. This may cover, for example, habitat creation that requires planning permission. Defra is still working through the scope of this exemption, including whether supporting access, management and monitoring infrastructure should be included. It is expected to be introduced in a second wave of secondary legislation later in 2026.
- The third exemption, for development enhancing parks, public gardens and playing fields, is likely to be of more limited use. It will apply only in narrow circumstances and not where the development forms part of a wider scheme or affects on-site priority habitats.
A proposal to allow certain biodiverse features in vegetated gardens to count towards BNG will not be taken forward, due to monitoring and compliance concerns.
4. Changes to the BNG statutory metric
The Government intends to digitise the BNG metric tools to improve usability and reliability. This will be part of the work to reform the SRM towards the end of 2026.
5. New low impact based exemption
The Government has confirmed that it is considering a new low impact based exemption for larger sites, for certain types of development where "the application of BNG is disproportionate to the benefits". The types of development that may be exclude include: change of use; installation of solar panels on industrial buildings; upwards extensions of large apartment buildings; and the replacement of petrol stations with an EV charging station. We can expect a further announcement about this alongside the response to the ongoing consultation on the proposed residential brownfield BNG exemption.
April 2026 consultation: residential brownfield exemption
The April 2026 consultation regarding a proposed targeted exemption for brownfield residential development has been launched in response to evidence that BNG can be more complex and disproportionately costly on brownfield land than on greenfield sites. Here's what developers of major sites need to know.
Mixed-use schemes may be excluded
The proposed exemption would apply only to development that is “predominantly residential”. How that will be measured – by floorspace, revenue or site area – has not yet been decided. Depending on how “predominantly residential” is defined, mixed-use and commercially led schemes with only a limited residential component may not qualify.
Definition of "brownfield"
Defra proposes that at least 75% of the land within the red line boundary must be previously developed land (PDL), based on lawful permanent buildings or structures dating from 1948 onwards. Hardstanding, roads and fixed surface infrastructure would count, but agricultural and forestry buildings, and minerals or landfill sites, would not. Some sites that fall within the NPPF concept of PDL may fail this proposed test.
Area thresholds
To target sites where BNG has the most disproportionate impact on viability, the Government is considering a range of area thresholds to which the exemption would apply, from 0.5 hectares to 2.5 hectares.
Next steps
As regards the proposed residential brownfield exemption, developers of brownfield and mixed-use schemes should consider how the proposed 75% PDL test and the unresolved “predominantly residential” definition could impact their developments, and respond to the consultation before it closes on 10 June 2026 – whether individually or through an industry body.
As to the other changes to the current BNG regime, we can expect to see the introduction of the temporary development exemption as early as end July 2026, followed by the residential brownfield exemption, the biodiversity-purpose exemption, the parks/public gardens/playing fields exemption, and updates to the statutory metric later in 2026.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
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