What is Biodiversity Net Gain?

Jun 22, 2023

Biodiversity Net Gain (BNG) is an approach to development and planning which aims to leave the natural environment in a measurably better state than beforehand. The objective is that development will impact the environment in a positive way by delivering improvements to ecological networks and the key point is that the improvement is measurable.

What is the requirement?

The Environment Act 2021 requires all planning permission to be granted subject to a deemed condition which imposes a requirement for a 10% increase in biodiversity on or near a development site. The Biodiversity Net Gain requirement will apply to developments covered by the Town and Country Planning Act 1990, unless exempt, from November 2023. The Biodiversity Net Gain requirement will apply to small sites from April 2024. That being said, some local planning authorities are already expecting applicants to demonstrate Biodiversity Net Gain.

How will it operate?

The condition will prevent commencement of the development until a Biodiversity Net Gain plan has been submitted and approved by the local planning authority, which sets out how the gain will be achieved. As the Biodiversity Net Gain requirement is a deemed condition, it exists in statute prior to the grant of planning permission. Therefore, applicants will not necessarily need to submit the plan after planning permission has been granted. For the more straightforward planning applications the plan could be submitted together with the application.

The plan should follow a mitigation hierarchy which compels applications to first avoid the harm, then mitigate and then finally compensate for the losses. The plan will only be approved if the biodiversity value on site post-development exceeds the pre-development biodiversity value of on site by 10%. The biodiversity value is calculated based on credits assigned to biodiversity units. So, for example, if the site is worth 50 biodiversity units before development, it will need to be worth 55 on completion. On-site biodiversity enhancement must be maintained for at least 30 years after completion of a development and this will be secured by the condition, a planning obligation and a conservation covenant. However, it is currently unclear how the ongoing maintenance will be monitored in practice.

If on-site biodiversity loss is unavoidable then alternative methods of meeting the objectives can be investments into off-site wildlife areas, which are recorded on the biodiversity gain site register, or purchasing statutory biodiversity credits if the developer can demonstrate that they are unable to achieve Biodiversity Net Gain through the on-site or off-site options. Where off-site payment is approved a biodiversity metric, developed by Defra and Natural England, will be used to calculate how many credits the developer will need to pay for in order to offset their biodiversity loss. The credits can be purchased from the Secretary of State and will be valued higher than the market value, so their availability does not discourage development of local market schemes and non-credit biodiversity schemes.

Are there any exceptions?

The consultation proposed that the exemptions will include:

  • Developments impacting habitat area below a minimal threshold
  • Householder applications
  • Change of use applications

Further exemptions are being considered for the creation of biodiversity gain sites and self-build and custom housebuilding. The consultation also proposed that some exemptions previously discussed would not apply including:

  • Brownfield sites (that meet set criteria)
  • Temporary permissions
  • Developments for which permitted development rights are not applicable due to being in a conservation area or national park

How the BNG requirement will affect developers

The requirement is quite onerous on developers and there is concern as to the increased bureaucracy and the resulting increase in costs. As with any new addition to the process it may take some time to workout how best to deal with the requirement and the already overstretched planning authorities will also have to iron out the kinks and this may lead to delays in planning consents.

Despite the potential difficulties which developers face in satisfying the condition Natural England have highlighted that the requirement means developers are less likely to face objections to their planning applications on the grounds of nature conservation or ecological harm.

Whilst we are not qualified to advise you on specific planning matters, we are able to assist you with any legal queries and are now well versed in dealing with developments which will need to start demonstrating an improvement in biodiversity and which will, in the future, be subject to this mandatory requirement. If you wish to get in touch, please contact our Real Estate department.

This reflects the law and market position at the date of publication and is written as a general guide. It does not contain definitive legal advice, which should be sought in relation to a specific matter.

Liz Hailey

Liz Hailey

Partner, Head of Property Law

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