Environmental watchdog urges caution over changes to biodiversity net gain rules

Defra launched the consultation in May, setting out proposals to implement biodiversity net gain (BNG) for small development, medium development and brownfield development.

Introduced under the Environment Act 2021, BNG requirements are designed to ensure that a development has a measurably positive impact ('net gain') on biodiversity, compared to what was there before development.

Since February 2024, most major developments have been subject to the requirements, with minor development following in April 2024.

The consultation - which closed last month - reported that early information suggests BNG implementation has been "broadly successful".

However, it said some "smaller developments and specific types of development are finding the operation of BNG is not as effective as could be".

The consultation document detailed complaints from developers about increased costs and additional steps involved in the planning process, as well as increased costs from delivering the habitat enhancements where sites may be more constrained.

In light of the difficulties, the consultation proposed the following improvements:

• reform of existing exemptions and introduction of new exemptions
• streamlining the small sites metric and considering whether this could apply to medium development
• relaxation of the biodiversity gain hierarchy and disapplication or amendment to the spatial risk multiplier for minor development
• delivery of compensation for development on brownfield sites with open mosaic habitat, applicable to all development categories

Responding to the proposals, the Chair of the Office for Environmental Protection, Dame Genys Stacey, recommended Defra approach reform to BNG "with caution" and levelled criticism at the lack of information in the consultation document.

She wrote: "The consultation includes proposals for significant design and methodological changes to BNG to address apparent challenges in its implementation.

"However, the consultation does not present any detailed evidence regarding the nature and extent of the challenges that the proposals are intended to address.

She also suggested that the consultation document did not include any assessment of the anticipated impact of the proposed reforms.

"As a consequence, the basis for which Government is making these particular proposals is not clear from the consultation," she said.

She went on to recommend Defra provide "fuller evidence" - including an evidence pack with an impact assessment - to support the need for reform, and for the proposals and their effects.

The response also highlighted some concerns over the proposals, including a claim that plans to exempt minor development would "significantly narrow the scope" of biodiversity net gain and is likely to lead to habitat loss across small-site developments.

It also said that the proposals to exempt minor development may adversely affect the nascent biodiversity unit market.

A Government spokesperson said Defra would respond to the OEP in due course, adding: "This Government is fully committed to Biodiversity Net Gain.

"We have consulted to make it easier, quicker, and cheaper for developers to deliver gains for both developers and nature."

Adam Carey