Learn more about the metric, ongoing maintenance and when net gain should be considered in the design process
The requirement for major new developments to provide a Biodiversity Net Gain (BNG) of at least 10% will be implemented from January 2024 (which is a change from the original November 2023 implementation date).
Developers of major developments must submit a BNG Plan alongside their planning application once they have assessed their site and developed an uplift strategy with the help of an ecologist.
Nick White, Principal Adviser on Net Gain for Natural England, reports that the development community appears generally well prepared. The Biodiversity Metric for calculating net gain, alongside guidance on how to use it, has been available for two years. He says BNG is already starting to look like business as usual for some of the largest commercial developers.
What levels of competency is needed for smaller developments?
The concern, he says, is that there are signs that some smaller developers and their consultants are not as well prepared.
For smaller developments – 10 dwellings or fewer – BNG requirements do not come into force until April 2024 (tbc). A simplified version of the metric can be used and there is no formal requirement to engage with an ecologist. But a level of competency will still be required to identify habitat types for the metric, for instance, and to understand the metric’s biodiversity hierarchies and its currency of onsite and potentially offsite ‘biodiversity units’.
Natural England is urging small practices to take advantage of the numerous CPD training events on BNG that at being offered, such as the RIBA Academy’s free Biodiversity Net Gain Policy Update event on 8 November 2023.
Is a 10% uplift achievable?
Most small-scale housing development takes place on sites with relatively low biodiversity value, so delivering a 10% uplift when the biodiversity value is low should be easily achievable, White points out.
‘If you are constructing on a site that’s got little or no pre-existing biodiversity value, which for many urban sites might be the case, then doing BNG within your site boundary red line should be comparatively straightforward.’
Watch our webinar 'Mandatory Biodiversity Net Gain is imminent: Are you ready?'
He continues: ‘However, if you are building on a site that has some kind of existing biodiversity that is more valuable for nature, then bringing BNG within your red line will be more challenging, and in some circumstances will be nonsensical. Trying to squeeze in high-quality features may not work ecologically.’
In these circumstances, developers can purchase offsite BNG units. As a last resort, developers will be able to purchase biodiversity credits, but these will be deliberately priced to be least attractive.
When should BNG appear in the design process?
White says it is important that architects appreciate that the earlier you consider BNG in the design process, and the earlier you engage with other professionals such as ecologists or landscape architects, the easier it will be to deliver uplift. The Biodiversity Metric can be used as an iterative design tool to test BNG options, so architects should make sure they understand how it works and put it to use, he adds.
The alternative of trying to introduce green components into a full drawn scheme is obviously going to be far more difficult.
He also says designers should remember that BNG will need to be managed and maintained for 30 years, which may have access implications and so should be considered in housing layouts. White also encourages developers to be realistic on what onsite BNG units are possible. For example, if the habitat requires regular grazing, this might be more challenging in an urban area.
What are habitat banks?
Where a developer needs to offset BNG, this can, in theory, be done anywhere in England, although the metric operates under a proximity principle that assigns greater value to offsite biodiversity units located closer to the development.
‘The policy encourages you to look onsite first, and then if you need to go off site to explain why that has to be the case,’ White says. ‘It could be that it would not work ecologically on site. It then encourages you to deliver BNG locally, either within the planning authority’s own boundary or within the relevant national character area for that part of the country.’
There is a BNG offsetting infrastructure already starting to develop. White says most small developers will be looking for local ‘habitat banks’, because these are likely to be the most cost-effective way to purchase small numbers of BNG units.
These habitat banks can be operated by any landowner, such as a local farmer, an environmental NGO or the local authority itself. Planners will only be able to consider offset units from banks that are on a national register that will become live in time for the commencement of the new BNG regime.
We will also see private sector BNG brokers emerging, who will sell biodiversity units to developers via an online trading platform. Some of the largest housebuilders are already setting up their own brokerage partnerships with NGOs, White reports. BNG is already spawning its very own trading sector.
Thanks to Nick White, Natural England.
RIBA Core curriculum topic: Sustainable architecture.
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