Navigating the New Biodiversity Net Gain Requirements: A Guide for Developers

  • Legal Development 13 February 2024 13 February 2024
  • UK & Europe

  • UK Real Estate Insights

Yesterday, the long-awaited Biodiversity Net Gain (BNG) Regulations came into force. Under these Regulations, major developments in England are required to deliver 10% BNG (subject to minor exceptions). The same requirement will be extended to smaller developments from April 2024, and NSIPs at the end of 2025.

A major development is one that involves:

  • the provision of 10 or more dwellinghouses (or dwellinghouses on a site over 0.5 hectares if it is not known whether the development has 10 or more dwellinghouses); 
  • the provision of 1,000 square metres or more of floorspace; 
  • development of an area of 1 hectare or more;
  • use of land for extraction of minerals (including preparation for extraction) or mineral-working deposits; or
  • waste development.

Developers are now required to ensure that all major development achieves a minimum 10% uplift (depending on the area) in the biodiversity value attributable to a proposed development against the pre-development baseline. This applies irrespective of whether the development impacts existing biodiversity. Accordingly, all planning applications for major developments must evidence an ability to meet this 10% uplift. 

This insight distils the key requirements that developers should bear in mind when seeking planning permission for a qualifying development. 

Calculating 10%

The process of assessing the baseline is complicated by the fact that there are three distinct types of biodiversity units:

  1. Area habitat units (such as grasslands, woodlands, and mudflats);
  2. Linear hedgerow units; and
  3. Linear watercourse units. 

The requirement to deliver 10% BNG applies to each type of unit and cannot be transferred between the distinct habitat types. For example, if a development has a negative effect on biodiversity in a watercourse (such as a river), then measures to enhance biodiversity in a nearby woodland will not be sufficient. 

Developers need to be conscious of the type of habitat that exists on site for the purposes of fulfilling BNG obligations. It is likely that on the most complex sites at least two of the three distinct habitat types will be found and, therefore, 10% BNG will need to be provided in respect of each impacted habitat. Any proposed mitigation and enhancement measures must align with the type of habitat that is being affected. 

The BNG metric tool is available to developers to determine how many biodiversity credits would be required to enable a development to meet its 10% BNG requirement. To ensure that the metric tool is used properly developers must be mindful of the types of habitat on site (both present and planned) as well as the condition of each habitat type. 

The BNG Hierarchy and Biodiversity Gain Plans

In theory, the 10% gain can be secured in three ways: 

(i)   On-site gains;

(ii)   Off-site gains; and/or

(iii)  Through the purchase of biodiversity credits. 

Developers must, however, first explore the possibility of achieving the 10% enhancement through on-site measures, turning only to options (ii) and (iii) where on-site provision is not possible. Of the two off-site options, the purchase of biodiversity credits should always be a last resort. 

Any planning permission granted pursuant to an application for major development will now be deemed to incorporate a planning condition which restricts commencement of development unless and until a Biodiversity Gain Plan has been approved by the local planning authority. As such, upon the grant of planning permission, developers must submit to the local planning authority a Biodiversity Gain Plan to demonstrate that the biodiversity gain objective has been met. This plan must then be approved prior to the commencement of the development.  

Developers should, therefore, consider how developments can incorporate BNG on-site. If a development is sufficiently early in its design-stage, then it may prove easier (and more cost effective) to introduce mitigation measures and/or the provision of on-site habitat as part of the development itself. 

This early consideration may save developers the high fees associated with purchasing biodiversity credits or off-site biodiversity units.

Management, Monitoring and Maintenance

In certain circumstances, the BNG obligations continue well into the lifetime of the development. On-site enhancements which contribute significantly to BNG, as well as all off-site enhancements, will require developers to commit by way of a planning condition (or potentially a legal agreement, such as a s106 Agreement or a conservation covenant), or potentially, a legal agreement, such as a s106 Agreement, or a conservation covenant, to the following:

  • Ongoing management and monitoring of BNG; and
  • A commitment to maintain the BNG for at least 30 years.

Unhelpfully, it is not entirely clear what constitutes a ‘significant’ on-site enhancement as this will vary on a project by project basis. One example given is that improving a habitat’s condition from ‘poor’ to ‘moderate’ would indicate that this is a significant enhancement. Other indicators include where habitat distinctiveness is increased or where habitats are originally assessed as being of medium or higher distinctiveness. This implies that there is a relatively low threshold as to what would be deemed as ‘significant’ for the purposes of the new Regulations. This, however, will be a matter of construction and, no doubt, will become clearer with the passage of time as developers, consultants and local planning authorities begin to grapple with the practical application of this requirement. 


All major developments now need to provide 10% BNG. Whilst a Biodiversity Gain Plan does not need to be submitted until after the planning permission has been granted, it is prudent to consider how 10% BNG will be delivered as early as possible. In addition to potential costs savings (by avoiding the higher costs associated with off-site mitigation or biodiversity credits) this may also assist developers to avoid programme delays as local planning authorities adjust to the new Regulations.


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