Biodiversity Net Gain (BNG) – What is it, and Why Developers Need to Know About It?   

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Since the 1970s, wildlife abundance in the UK has declined by 13%, according to the latest “State of Nature Report”, published in 2019.

BNG aims to leave the natural environment in a measurably better state than it was beforehand, and BNG represents a flagship initiative to generate regulatory demand for habitats and nature recovery in England (note, for Wales please see our NBB article here.)

Schedule 7A of the Town and Country Planning Act 1990, amended by the Environment Act 2021, makes BNG mandatory on all developers, and obliges them to generate a minimum 10% gain in biodiversity in most development proposals for large sites (with some exceptions and see below for small sites), to be maintained for at least 30 years. Applicable development projects will be required to produce a “biodiversity gain plan”, which will need formal approval from the local planning authority before commencement.   

The “minimum 10% gain” is calculated using DEFRA’s “Biodiversity Metric” and demonstrated in a biodiversity gain plan to be produced by developers. Biodiversity will be delivered on-site, off-site on third party land or via a new statutory biodiversity credit scheme. It should be said that 10% is a minimum threshold, and some local planning authorities are already implementing higher percentages, such as Guildford, Brighton and Hove, and Worthing councils. Kingston Upon Thames and Tower Hamlets are developing policies through their local plan process that may require a minimum of a 30% net gain in biodiversity.   

In terms of the costs of BNG, the Government’s impact assessment estimates net gain delivery costs are likely to be low as a proportion of key variables such as build costs and land prices:  

  • Brownfield residential development: 0.1% to 0.8% of build costs  
  • Greenfield residential development: 0.1% to 3.9% of build costs  
  • Commercial / non-residential development: expected to be less than 5% of land value. 

This is just an estimate. BNG is implemented by planning conditions or obligations. If LPAs prefer the latter route they can charge application and monitoring fees. They can also require a bond from a developer for the carrying out of BNG works.  

What are the timescales for BNG requirements? 

The timescales are already running for most developments; from 12th February 2024, planning permissions granted in England for large sites will have to deliver at least a 10% net gain. For small sites, the BNG requirement on planning permissions starts on 2nd April 2024. BNG will be a requirement for Nationally Significant Infrastructure Projects from November 2025.  

The next stage for BNG 

Natural England/DEFRA developed a metric for measuring the ‘net gain’ approach. The metric uses habitat features including the size of the habitat, its distinctiveness, condition, quality, strategic significance and location, to determine how many biodiversity units are available.  Developers need to understand the metric as it drives the costs associated with complying with BNG.  

The developer must use the mitigation hierarchy to avoid, mitigate and compensate losses to achieve an overall ‘no net loss’, and then deliver at least a 10% gain in the metric biodiversity units value to meet the Environment Act requirements. This provides a quantitative approach to biodiversity net gain.  

BNG is a complex regime underpinned with 6 sets of regulations and with more to come, as well as the metric and various templates. It presents a steep learning curve for all concerned. It is believed that many overstretched and under resourced local planning authorities are still getting to grips with BNG. It would be prudent for developers in England to factor in the possibility of delays to schedules as the new regime starts to bed in.   

Our Head of Environmental, Climate and Sustainability Law, Stephen Sykes, alongside expert Planning solicitor, Tom Jones, recently hosted the first of a series of webinars on BNG. To watch the webinar on-demand and gain legal insights into BNG and NBB, please clickhere.