Summary of CIEEM’s Response to the Biodiversity Net Gain Brownfield Exemption Consultation

1. CIEEM strongly opposes the proposed area-based exemption from Biodiversity Net Gain (BNG) requirements for residential brownfield development.
2. The proposals wrongly equate previous land use with ecological value. Brownfield sites are not inherently of low biodiversity value and can support important habitats, species and opportunities for nature recovery, particularly in urban areas. Decisions about BNG eligibility should therefore be based on ecological evidence using the Biodiversity Metric, rather than arbitrary thresholds based on site size or the proportion of previously developed land.
3. The proposals are contrary to the core principle of BNG, which is to secure measurable improvements for biodiversity through development. CIEEM is particularly concerned that the proposed brownfield exemption, when combined with existing and forthcoming exemptions (de minimis and the 0.2ha exemptions, respectively), could remove up to 90% of planning applications from BNG requirements. This would be inconsistent with Government commitments that “most development” should contribute to nature recovery.
4. The consultation presents no evidence that biodiversity requirements are delaying or preventing brownfield development. The Government’s own evidence in the Planning and Infrastructure Bill impact assessment stated that there is little indication that nature is blocking development. For brownfield development, we suggest that remediation costs are likely a much greater constraint on brownfield viability than ecological requirements.
5. CIEEM supports a “brownfield first” approach to development, but not at the expense of biodiversity. Early ecological involvement should be an integral part of the planning process, helping developers to avoid high value biodiversity sites in the first instance, and then identify opportunities to enhance biodiversity and create better places for people and nature.
6. The proposals undermine confidence in emerging nature markets that have developed around BNG and are helping to attract private investment into nature recovery. Reducing the number of developments required to deliver biodiversity gains risks weakening demand for habitat creation and enhancement projects.
7. There are significant concerns about social justice. Recent research shows that the proposed exemption would disproportionately affect deprived urban communities, where access to nature is already poorest and where brownfield development is most concentrated. As a result, the exemption risks embedding environmental inequality into the planning system and creating a two-tier approach to nature access.
8. CIEEM challenges the assumption that the exemption would simplify the planning process. Determining whether land qualifies as previously developed may require extensive historic evidence and could create additional bureaucracy, uncertainty and disputes. In many cases, it would be simpler, quicker and more transparent to undertake a proportionate ecological assessment using the Biodiversity Metric.
9. Overall, CIEEM concludes that no new brownfield exemption should be introduced. Instead, Government should retain an evidence-based approach that assesses biodiversity value directly, ensures development contributes fairly to nature recovery, and recognises the important role of professional ecologists in delivering sustainable development.