Biodiversity Net Gain Changes 2026

Biodiversity Net Gain (BNG) has been a key part of England’s planning system since it became mandatory in 2024 under the Environment Act 2021. The policy requires most developments to deliver at least a 10% increase in biodiversity compared to the site’s original ecological value.

In simple terms, development should leave nature in a better state than it was before.

Since its introduction, BNG has had a major influence on the planning process. Developers must assess existing habitats, calculate biodiversity value using the statutory metric, and demonstrate how the project will achieve a net gain through habitat creation, enhancement, or off-site biodiversity units.

However, Biodiversity Net Gain updates in 2026 are set to reshape how the system works. The government has proposed several reforms aimed at reducing administrative burdens for smaller developments while extending the policy to larger infrastructure projects.

For planners, developers, and landowners, these BNG changes in 2026 could significantly affect both project timelines and costs.

In This Article

1. What is Biodiversity Net Gain / BNG

2. The Key Biodiversity Net Gain Changes Expected in 2026

3. The Proposed 0.2 Hectare BNG Exemption

4. What the BNG Changes Mean for Current Planning Applications

5. Implications for Developers and the Planning Industry

6. Environmental Concerns About the BNG Updates

7. What Happens Next

What is Biodiversity Net Gain (BNG)?

Biodiversity Net Gain (BNG) is a planning and environmental policy that requires developments to leave nature in a better state than before. Introduced in England under the Environment Act 2021, it became mandatory for most new build developments in 2024.

In practice, this means:

• Developers must assess the ecological value of a site before construction.

• Any impacts on habitats or species must be offset or enhanced.

• Projects are expected to achieve at least a 10% increase in biodiversity, measured through a recognised biodiversity metric.

• Gains can be delivered on-site (new habitat creation, planting) or off-site via habitat banks and biodiversity credits.

BNG aims to reverse biodiversity loss, protect wildlife, and ensure that development is nature-positive.

The Key Biodiversity Net Gain Changes Expected in 2026

The most significant reform currently proposed is a new area-based exemption for small development sites. At present, only extremely small developments (affecting below 25 square metres of habitat) are exempt from BNG requirements. The government has recognised that this threshold is impractically low and has proposed replacing it with a much larger exemption.

The main Biodiversity Net Gain updates expected in 2026 include:

• A new exemption for sites under 0.2 hectares (approximately 2,000 sqm)

• Simplified compliance routes for small and medium developments

• A proposed exemption for residential brownfield sites up to 2.5 hectares (currently under consultation)

• Extension of mandatory BNG requirements to Nationally Significant Infrastructure Projects (NSIPs) from May 2026

These changes are intended to streamline the system, particularly for small housing developments and urban infill sites, while ensuring that larger projects continue to deliver meaningful environmental improvements.

The Proposed 0.2 Hectare BNG Exemption

The introduction of a 0.2 hectare exemption is the most talked-about element of the Government BNG updates. If implemented, it would remove biodiversity net gain requirements for many smaller development sites.

Currently, even modest projects must complete ecological assessments and demonstrate how they will achieve the 10% biodiversity uplift. For small schemes, this can create disproportionate costs and delays.

Under the proposed changes, developments such as small housing schemes or compact urban sites would no longer need to prepare biodiversity metric calculations or secure off-site habitat compensation.

Government analysis suggests that if this exemption had been in place since the introduction of mandatory BNG in 2024, over 40% of planning applications could have been exempt. This highlights how widely the change could affect the planning system once implemented.

What the BNG Changes 2026 Mean for Current Planning Applications

Despite the announcements, the BNG changes for 2026 are not yet law. As of March 2026, the government is still finalising consultation responses and preparing the necessary secondary legislation.

Until the updated regulations come into force, the existing BNG rules remain fully applicable. This means that planning applications submitted today must still demonstrate a 10% biodiversity net gain, regardless of site size.

This transitional period has created some uncertainty within the development industry. Some developers with sites close to the proposed 0.2 hectare threshold may consider delaying applications in the hope that the exemption becomes available before submission.

However, there is currently no confirmed implementation date, and retrospective exemptions are unlikely. Projects already submitted or approved will almost certainly continue to be assessed under the existing framework.

Implications for Developers and the Planning Industry

For many developers, particularly small and medium-sized housebuilders, the proposed reforms could significantly simplify the planning process.

Smaller sites have often found BNG compliance challenging because ecological surveys, metric calculations, and off-site unit purchases can represent a substantial proportion of project costs.

If the exemptions are implemented, the benefits for developers could include:

• Reduced ecological reporting and consultancy requirements

• Lower planning and compliance costs

• Faster planning submissions and approvals

• Improved viability for small housing schemes and urban infill developments

At the same time, larger developments will continue to deliver biodiversity improvements, ensuring that significant projects still contribute to habitat creation and ecological recovery.

Environmental Concerns About the BNG Updates

While many in the development sector support the reforms, environmental groups have raised concerns about the potential impact on biodiversity.

Some analysts suggest that a large proportion of planning applications could become exempt from BNG requirements if the new thresholds are introduced. Critics argue this could reduce opportunities to create urban habitats and ecological corridors, particularly in areas where smaller developments are common.

Others argue that the policy should focus on developments with meaningful ecological impact, rather than placing administrative burdens on very small sites with limited potential for habitat enhancement.

As with many planning reforms, the debate reflects the challenge of balancing environmental protection with housing delivery and economic growth.

What Happens Next

The government is expected to publish further guidance and legislation confirming the Biodiversity Net Gain changes for 2026 in the coming months.

Until then, developers and planning professionals should assume that the current BNG requirements remain fully in force. Monitoring official updates will be important as the policy evolves.

The upcoming reforms could mark the first major adjustment to Biodiversity Net Gain since its introduction, potentially reshaping how the policy operates across thousands of planning applications each year.

For anyone involved in development, planning, or land management, understanding these BNG updates and exemptions will be essential as the system continues to develop.