Biodiversity Net Gain (BNG) represents one of the most significant changes to the planning system in recent years. While the principle of improving biodiversity outcomes is well established, the statutory requirement for measurable net gain introduces new processes, obligations and risks that developers and operators must now navigate as part of the planning process.

For commercial development, understanding how BNG applies in practice is essential to managing programme, cost and deliverability.

What is Biodiversity Net Gain?

Biodiversity Net Gain is a requirement that development should leave biodiversity in a measurably better state than before. In England, this is generally expressed as a minimum 10% uplift in biodiversity value, calculated using a standardised metric.

The objective is to ensure that development does not simply mitigate harm, but actively contributes to ecological improvement. This marks a shift from earlier approaches, which focused primarily on avoidance and mitigation of impacts.

When BNG applies

BNG applies to most planning applications for development in England, subject to specific exemptions and transitional arrangements. It is not limited to large-scale or greenfield schemes and can apply to relatively small commercial developments, including changes of use and redevelopment of previously developed land.

There are exemptions for certain types of development, such as some householder applications and small-scale self-build projects, but these are narrow. Assuming that BNG does not apply because a site is previously developed or constrained can be a common and costly mistake.

How biodiversity value is assessed

Biodiversity value is assessed using a nationally prescribed metric, which assigns units based on habitat type, condition, distinctiveness and strategic importance. The baseline position is established by surveying the existing site, and the post- development position is then calculated to determine whether net gain is achieved.

This process introduces a level of technical assessment that many commercial developers may not previously have encountered, even where ecological issues were limited.

Importantly, the metric is not a judgement of ecological quality in a general sense, but a scoring tool. Small changes in habitat classification or condition can have a disproportionate effect on unit calculations.

Delivering BNG: on-site, off-site and credits

BNG can be delivered in three main ways:

On-site provision

Where possible, biodiversity enhancements can be delivered within the red line boundary of the site. This may include new planting, habitat creation, green roofs or landscape- led design features. On constrained commercial sites, however, opportunities for meaningful on-site gain can be limited.

Off-site provision

Where on-site delivery is not achievable or sufficient, biodiversity units can be delivered off-site, either on land controlled by the applicant or through third-party providers. Off-site provision introduces additional considerations around land control, long-term management and legal agreements.

Statutory credits

As a last resort, developers may purchase statutory biodiversity credits. These are intended to be used only where on-site and off-site options are not available and are priced to encourage delivery through other means.

The delivery route chosen can have significant implications for cost, timing and legal complexity.

Securing BNG through planning

BNG is typically secured through planning conditions and, in many cases, legal agreements. This often includes requirements for the submission and approval of a biodiversity gain plan, as well as mechanisms to secure long-term management of habitats, usually for a minimum period of 30 years.

The timing of these requirements is critical. Conditions that operate as pre- commencement conditions can delay the start of development if not addressed early, while obligations linked to occupation or use can affect operational programmes.

Common issues and risks

A number of recurring issues are emerging in practice:

  • Late consideration of BNG, leading to redesign or delay
  • Assumptions that previously developed land will automatically score low risk
  • Underestimating the time required for surveys, metric calculations and approvals
  • Lack of clarity over who is responsible for long-term management and monitoring
  • Tension between landscape design objectives and biodiversity scoring outcomes

For commercial schemes operating to tight programmes, these issues can create avoidable uncertainty if not addressed at an early stage.

BNG and proportionality

While BNG is a statutory requirement, it is still subject to the principle of proportionality. The level of detail and supporting information required should be appropriate to the scale and nature of development.

Clear scoping at the outset, and early dialogue with the local planning authority, can help ensure that biodiversity considerations are integrated sensibly into the planning strategy rather than treated as an afterthought.

Practical approach for commercial development

From a practical perspective, BNG is best managed by:

  • Identifying at an early stage whether BNG applies and to what extent
  • Establishing a robust baseline position
  • Exploring realistic on-site opportunities alongside off-site options
  • Integrating biodiversity strategy into the overall planning and delivery programme
  • Ensuring that conditions and obligations are clearly understood and capable of implementation

This approach allows biodiversity considerations to be aligned with commercial objectives and reduces the risk of delay once consent is granted.

Summary

Biodiversity Net Gain introduces a new layer of assessment and delivery into the planning process for commercial development. While it presents challenges, particularly on constrained sites, it can be managed effectively through early assessment, clear strategy and proportionate implementation. Understanding how BNG operates in practice is now an essential part of planning risk management and project delivery.

Disclaimer
This article is provided for general information only and does not constitute planning advice. Planning matters are site-specific and subject to change. Professional advice should be sought before taking action in relation to any particular site or proposal.