CIEEM Needs You: Brownfield BNG Exemption Consultation

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The UK Government has launched a consultation on proposals to exempt certain brownfield developments from mandatory Biodiversity Net Gain (BNG) requirements for housing, which closes on 10 June 2026. This follows closely behind the soon-to-be introduced 0.2 hectare exemption (for all development) and proposed changes to temporary planning permission exemptions.

Taken together, these changes risk significantly weakening the effectiveness of BNG in England and undermining the Government’s repeated commitments to nature recovery.

BNG was designed to ensure that development contributes positively to nature recovery while providing certainty and consistency for developers. Successive exemptions now risk eroding that principle to the point where the policy becomes ineffective in practice.

CIEEM urges members to engage with the consultation and help ensure that future planning reforms support both sustainable development and meaningful nature recovery.

CIEEM encourages all members to respond

It is essential that ecologists and environmental professionals engage directly with this consultation. Defra counts every unique consultation response individually, and detailed responses from practitioners carry significant weight.

Members are strongly encouraged to:

  • respond directly to the consultation questions;
  • use CIEEM’s response (due to be published shortly) as supporting material rather than simply stating agreement with it; and
  • provide evidence and examples from your own professional experience.

Generic or campaign-style responses are often grouped together by Government analysts, whereas unique responses are counted separately and can have greater influence on final policy decisions.

Even the consultation acknowledges the risks to nature recovery

Importantly, the consultation paper itself recognises the significant risks associated with expanding exemptions to BNG requirements. It states:

“Taken together, these results highlight that some of the proposed exemption thresholds could lead to substantial ecological and market impacts that need to be considered against any potential housing gains. Increasing the area threshold for a brownfield exemption delivers progressively larger reductions in developer compliance costs, reflecting fewer sites required to undertake onsite habitat creation, secure off-site units, or purchase statutory credits. However, at the same time, higher thresholds lead to a greater volume of biodiversity units being foregone and therefore a higher cost to nature, reflecting the habitat that would otherwise have been delivered and its wider societal benefits.”

This is a significant acknowledgement from Government itself that the proposed exemptions could result in meaningful ecological harm and lost opportunities for nature recovery.

Brownfield-first development and nature recovery can work together

CIEEM supports a brownfield-first approach to development where appropriate. However, this should not mean that biodiversity considerations are removed from decision-making altogether.

Brownfield sites can contain significant ecological value, including priority habitats and important Open Mosaic Habitats (OMH). Early ecological involvement is essential to:

  • identify genuinely high-value sites;
  • avoid or minimise harm where possible; and
  • ensure development and nature recovery objectives are planned together from the outset.

Good ecology is not a barrier to good development. In many cases, it improves outcomes, reduces risk and helps create more sustainable and resilient places.

No evidence that biodiversity is blocking (brownfield) development

The Government has not presented evidence demonstrating that biodiversity requirements are significantly preventing brownfield housing delivery.

The consultation appears to proceed from an assumption that ecology and BNG are major barriers to development, yet no substantive evidence base has been published to support this claim, either on brownfield land specifically or within the planning system more broadly. CIEEM has previously published evidence that nature regulation is not holding back development – see here, here and here.

In reality:

  • remediation, contamination treatment, infrastructure upgrades and viability issues are typically likely to be far greater constraints on brownfield delivery than ecological assessment;
  • the BNG metric itself is straightforward to complete on genuinely low-impact sites; and
  • the cost and complexity of navigating multiple exemptions may now exceed the cost of compliance itself.

The cumulative effect of exemptions is deeply concerning

The proposed brownfield exemption cannot be viewed in isolation.

Alongside:

  • the new 0.2 hectare exemption;
  • the retention of the de minimis exemption (a process of self-declaring negligible impact, and which we have previously warned about here and here); and
  • the proposed exemption for temporary planning permissions,

there is a real risk of creating large-scale loopholes that allow significant biodiversity harm without compensation.

Improving ecological practice and confidence

CIEEM recognises that the quality and consistency of ecological reporting can sometimes be variable, including challenges around the under- or over-identification of habitats such as Open Mosaic Habitat.

This is an area where the profession is actively working to improve standards through:

  • enhanced training and skills development;
  • professional guidance;
  • BNG assurance discussions; and
  • upskilling ecologists in planning, development viability and wider “good development” principles.

CIEEM is working to support professional ecologists to understand not only the biodiversity, but also how ecology integrates with planning and development delivery.

Valuing the ecological profession

Findings from CIEEM’s recent State of the Profession survey show that many ecologists feel undervalued despite undertaking work that is critical to a sustainable and resilient future.

Government repeatedly framing ecology as a “blocker” risks undermining confidence in the profession and obscures the positive role that ecologists play in enabling sustainable development.

Nature recovery and housing delivery are not mutually exclusive goals. Effective ecological input helps to achieve both.