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Mandatory biodiversity net gain (BNG): government publishes guidance on irreplaceable habitats

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The Department for Environment, Food and Rural Affairs (Defra) has now published guidance on how mandatory biodiversity net gain (BNG) applies to irreplaceable habitats.

The mandatory requirement for developers to provide BNG for new planning applications under the Town and Country Planning Act 1990 (TCPA 1990) came into force in England on 12 February 2024. The planning condition requires at least 10% BNG for new planning applications for development under the TCPA 1990 that results in loss or degradation of habitat. This is subject to limited exemptions and BNG for small sites (of between one and nine dwellings) will apply from 2 April 2024.

Irreplaceable habitats are habitats that are very difficult to restore, recreate or replace once destroyed, due to their age, uniqueness, species diversity and rarity. The definition and list of irreplaceable habitats for BNG are set out in the Biodiversity Gain Requirements (Irreplaceable Habitat) Regulations 2024 (SI 2024/48). It includes ancient woodland, ancient and veteran trees, blanket bog, limestone pavements, coastal sand dunes, spartina saltmarsh swards, mediterranean saltmarsh scrub and lowland fens.

The National Planning Policy Framework (NPPF) policy on irreplaceable habitats means that planning permission for development resulting in its loss or deterioration will only be granted in wholly exceptional circumstances and with suitable compensation. Consequently, the 10% BNG requirement does not apply when irreplaceable habitats are lost as they are so difficult to recreate and have such a high biodiversity value that it would be impossible to achieve the requirement to increase biodiversity on top of no net loss.

To read the latest Government guidance on this topic see –

Tom Warrender


Tom Warrender


Tom is a Partner and Commercial Property Solicitor with a wealth of experience acting for clients both locally and nationally since 2005.