Biodiversity Net Gain (BNG) is continuing to shape how development is planned and delivered in England. With further changes confirmed by DEFRA, developers and landowners will need to reassess how schemes are designed, costed and brought forward from August 2026.

Following industry feedback and a review of the operation of the regime, DEFRA has now confirmed a series of important amendments designed to make Biodiversity Net Gain more proportionate, particularly for smaller developments, whilst maintaining the Government’s wider environmental objectives.

These changes will affect planning applications submitted on or after 6 August 2026, making it essential for developers, landowners and planning professionals to understand the new requirements.

Why Is BNG Being Updated?

Since becoming mandatory, BNG has significantly influenced site design, planning strategy and development viability. Whilst the principle of delivering measurable biodiversity improvements remains widely supported, concerns have emerged regarding the burden placed on smaller developments and the practical challenges of delivering biodiversity enhancements on constrained sites.

The latest amendments aim to simplify compliance, reduce costs for small-scale development and provide greater flexibility in how biodiversity gains are achieved.

Importantly, the Government’s commitment to delivering a minimum 10 per cent Biodiversity Net Gain remains unchanged.

Extension of BNG to Nationally Significant Infrastructure Projects

One of the most significant recent developments is the extension of mandatory BNG to Nationally Significant Infrastructure Projects (NSIPs).

From 2 November 2026, major infrastructure schemes including transport, energy and water projects will be required to deliver a minimum 10 per cent Biodiversity Net Gain.

Key points include:

• BNG will apply only to habitats affected by development rather than entire project boundaries.
• On-site and off-site biodiversity delivery will be permitted.
• Statutory biodiversity credits will remain a measure of last resort.
• The delayed implementation timetable is intended to allow project promoters sufficient time to adapt.

For infrastructure developers, early ecological assessment and strategic land planning will become increasingly important.

New small site exemption

Perhaps the most significant change for many developers is the introduction of a new exemption for very small development sites.

From 6 August 2026, development proposals on sites with a red-line boundary of less than 0.2 hectares will be exempt from the statutory Biodiversity Net Gain requirement.

This change is intended to address concerns that BNG compliance can be disproportionately costly and complex for small developments. For developers, self-build promoters and landowners bringing forward small sites, the exemption could remove a significant planning hurdle and reduce both consultancy and biodiversity unit costs.

However, applicants should note that wider environmental protections and planning policy requirements will continue to apply.

Temporary development exemption

DEFRA has also introduced a new exemption for temporary development.

Where planning permission is granted for a period of five years or less, and the entire development is temporary in nature, the scheme will be exempt from mandatory Biodiversity Net Gain requirements.

This is likely to benefit a range of developments including:

• Temporary construction compounds
• Certain event and leisure uses
• Short-term operational facilities
• Temporary infrastructure projects

Developers of genuinely temporary schemes may therefore see reduced ecological reporting requirements and lower project costs.

End of the self-build exemption

Whilst some developments will benefit from new exemptions, others will face additional requirements. The existing exemption for self-build and custom-build development will be removed for applications submitted on or after 6 August 2026.

This means that self-build developments which previously benefited from exemption may now be required to achieve the statutory 10 per cent Biodiversity Net Gain unless they qualify under another exemption, such as the new small site threshold.

Greater flexibility for minor development

Another welcome amendment relates to how minor developments can achieve Biodiversity Net Gain.

Previously, applicants were expected to demonstrate that on-site biodiversity enhancements had been fully explored before relying on off-site biodiversity units. Under the revised rules, applicants for qualifying minor developments will no longer be required to follow this sequential approach.

Instead:

• On-site and off-site options can be considered simultaneously.
• Developers can select the most practical and viable approach earlier in the process.
• Greater flexibility should reduce delays and simplify scheme design.

This is particularly beneficial for constrained sites where delivering meaningful on-site biodiversity gains may be difficult or commercially impractical.

What does this mean for developers?

The latest reforms demonstrate the Government’s attempt to balance environmental objectives with housing delivery and economic growth.

For developers and landowners, the key implications are:

• Sites up to 0.2ha will no longer require BNG compliance.
• Temporary developments may benefit from new exemptions.
• Self-build developers face additional obligations from 6 August, depending on site size.
• Minor developments will have greater flexibility in using off-site biodiversity units.
• Larger developments and infrastructure projects will continue to face robust biodiversity requirements.

Looking ahead

Do the amendments go far enough?  Exemption of sites under 0.2ha is a low threshold with many small developers still having to tackle the BNG as a mandatory requirement creating delays throughout the entire project from start to finish. 

Further refinements to Biodiversity Net Gain could help reduce the disproportionate burden on small developers by introducing a more clearly tiered and proportionate approach.  Whilst recent changes, including the small site exemption, are a positive step, a simplified “light-touch” metric for smaller developments would help reduce reliance on specialist input and associated costs.

Greater flexibility in how biodiversity gains are delivered would also improve certainty and speed at application stage. In practice, aligning BNG requirements more closely with the scale, complexity and viability of smaller schemes would support SME developers, encourage delivery on smaller sites and ensure that biodiversity objectives are met without creating unnecessary barriers to development.

For now Biodiversity Net Gain remains firmly embedded within England’s planning system and is unlikely to disappear as a development requirement. However, these latest amendments represent a more pragmatic approach, recognising that a “one-size-fits-all” model does not always work for smaller developments and in some cases, making development unviable.

Existing applications will remain subject to the current Biodiversity Net Gain requirements and the new regulations will not be applied retrospectively.

Understanding biodiversity constraints and opportunities at the earliest stage of site promotion remains the most effective way to avoid delays and ensure a smooth route through the planning process.