What is “Biodiversity Net Gain” and how it is impacting UK property development

What Is Biodiversity Net Gain (BNG)?

Biodiversity Net Gain is a new approach in UK planning and environmental policy that ensures new developments contribute positively to the natural environment. In simple terms, it means that any new property development must leave biodiversity in a measurably better state than it was before construction began.

BNG focuses on habitat creation, enhancement of biodiversity value, and maintaining a balance between development and nature recovery. The idea is to offset the environmental impact caused by construction by improving natural habitats either on-site or off-site.

Why the UK Introduced Biodiversity Net Gain

The UK Government introduced Biodiversity Net Gain as part of the Environment Act 2021 to tackle biodiversity loss and promote sustainable development. It became a mandatory requirement in 2024 for most new developments seeking planning permission.

The main goal is to integrate environmental responsibility into the planning process, ensuring that developers protect, restore, and enhance biodiversity for future generations.

How Biodiversity Net Gain Works

BNG requires developers to measure the pre-development biodiversity using a statutory biodiversity metric. This helps determine the biodiversity value of the land before any work starts. Afterward, developers must demonstrate how their project will result in at least a 10% net gain in biodiversity value once completed.

This can be achieved by:

• Enhancing on-site habitats
• Creating off-site biodiversity units
• Or purchasing statutory biodiversity credits from the UK Government as a last resort

The Core Principle of “Net Gain”

The phrase “net gain” means that developments shouldn’t merely replace what was lost but actively improve biodiversity. For example, if a natural habitat is destroyed during construction, developers must ensure an equivalent or greater habitat is restored or created elsewhere, achieving a measurably positive impact.

The Biodiversity Gain Plan Explained

A Biodiversity Gain Plan is a formal document submitted to local planning authorities. It details how a developer will meet the BNG requirements. This plan typically includes:

• Pre-development biodiversity assessments
• On-site and off-site improvement strategies
• Long-term management and maintenance commitments

Without an approved biodiversity gain plan, planning permission cannot be granted.

Pre-Development Biodiversity Assessments

Before breaking ground, a developer must measure pre-development biodiversity within the red line boundary of the project. Using the biodiversity net gain tool, they assess habitats, wildlife species, and vegetation to establish a baseline biodiversity value.

This baseline becomes the foundation for planning biodiversity enhancements and calculating the number of biodiversity units required for compliance.

On-Site vs. Off-Site Biodiversity Enhancements

Developers are encouraged to achieve BNG on-site whenever possible, by planting trees, creating green roofs, or enhancing on-site habitats.

However, if on-site improvements can’t meet the mandatory 10% net gain, developers can turn to off-site biodiversity gains. This could involve working with a land manager or buying statutory biodiversity credits to offset the loss elsewhere.

Biodiversity Units and Statutory Biodiversity Metric

BNG calculations revolve around biodiversity units, which measure the biodiversity value of a site based on its size, habitat type, and condition.

These units are calculated using a statutory biodiversity metric set by the UK Government. Developers must show that after development, the biodiversity units have increased by at least 10% compared to the pre-development state.

Purchase of Statutory Biodiversity Credits

When developers can’t deliver sufficient on-site or off-site biodiversity units, they may purchase statutory biodiversity credits. This allows them to meet legal obligations by funding government-led nature recovery projects elsewhere in the UK.

This mechanism ensures flexibility while maintaining a nationally consistent standard for biodiversity enhancement.

The Role of Local Planning Authorities

Local authorities play a key role in enforcing BNG compliance. They review and approve biodiversity gain plans, monitor implementation, and take enforcement action when developers fail to meet their commitments.

Local planning authorities ensure that every project aligns with both local biodiversity priorities and national environmental regulations.

Mandatory BNG Requirements for Developers

Under the new rules in England, most developments will need to:

• Deliver a minimum 10% biodiversity net gain (unless exempt)
• Submit a Biodiversity Gain Plan for approval before development begins
• Secure and manage habitat improvements for at least 30 years, usually through a legal agreement such as a conservation covenant or section 106

This makes BNG not just a formality but a legally responsible obligation under the planning and infrastructure bill.

How Biodiversity Net Gain Affects Property Development

For developers, BNG has changed how projects are designed and approved. Developers must now consider habitat creation, on-site enhancement, and off-site BNG options early in the planning process.

Although it adds upfront costs and complexity, it also provides long-term environmental and economic benefits, enhancing the local environment and the value of developments.

Nationally Significant Infrastructure Projects (NSIPs)

Large-scale projects, such as roads, railways, and energy facilities, also fall under BNG requirements. These nationally significant infrastructure projects must deliver measurable biodiversity improvements across vast areas, often through off-site biodiversity units or purchase of statutory biodiversity credits.

Biodiversity Gain Hierarchy: How to Achieve Compliance

The biodiversity gain hierarchy guides developers in meeting their obligations:

1. Avoid harming existing habitats.
2. Minimise unavoidable impacts.
3. Enhance biodiversity on-site.
4. Compensate off-site for any remaining loss.
5. Buy statutory biodiversity credits as a last resort.

This structured approach ensures developers explore all options before offsetting impacts elsewhere.

Off-Site Biodiversity Gains and the BNG Market

Off-site BNG is creating a growing market for biodiversity units. Landowners can now sell off-site biodiversity units to developers needing to offset losses. This not only supports nature recovery but also creates financial opportunities for rural land managers and farmers.

Benefits of BNG: Long-Term Value and Nature Recovery

Beyond regulatory compliance, Biodiversity Net Gain brings lasting environmental value. It promotes carbon sequestration, enhances natural habitats, supports wildlife, and contributes to climate change mitigation.

For developers, BNG can also improve brand reputation, boost property value, and ensure projects gain smoother approval from planning authorities.

Challenges Developers Face with BNG Compliance

While BNG offers many benefits, developers face challenges like:

• Limited on-site space for habitat creation
• Costs of buying statutory biodiversity credits
• Complexity in using the biodiversity net gain tool
• Difficulty finding suitable off-site biodiversity units

However, with proper planning, these challenges can be managed effectively.

BNG and Small Sites: Simplified Processes

To support small sites and local builders, the UK Government has introduced simplified BNG processes. These make it easier for small developers to achieve BNG without extensive costs, ensuring environmental benefits are delivered across all scales of development.

Conclusion

Biodiversity Net Gain (BNG) represents a transformative step in how the UK approaches property development. By making biodiversity enhancement a mandatory requirement, the policy aligns construction with nature recovery goals, ensuring a healthier and more sustainable environment.

From habitat creation to off-site biodiversity gains, BNG ensures that every development contributes to restoring and protecting the UK’s precious natural ecosystems for future generations.

FAQs

1. What is Biodiversity Net Gain (BNG)?
BNG is a planning requirement ensuring developments leave biodiversity in a better state than before construction.

2. How much biodiversity gain is required?
Developers must deliver at least a 10% measurable biodiversity net gain.

3. Can developers achieve BNG off-site?
Yes, if on-site improvements are insufficient, developers can use off-site biodiversity units or purchase statutory biodiversity credits.

4. Who oversees BNG compliance?
Local planning authorities are responsible for reviewing and enforcing BNG plans.5. Why is BNG important for the environment?
It helps reverse biodiversity loss, promotes habitat creation, and supports climate change mitigation efforts.

Disclaimer:

This article provides general information only and should not be taken as planning, legal, or ecological advice. Developers should seek professional guidance tailored to their specific project