Biodiversity Net Gain: One Year In
The mandatory BNG requirement for all planning applications turned one. What the data shows about compliance, ambition, and the gap between ecology and planning
Mandatory Biodiversity Net Gain — requiring all planning applications to demonstrate a minimum 10% net gain in biodiversity units — became law in February 2024. The first year of data from London applications shows widespread compliance at the minimum level, and a handful of schemes demonstrating genuine ambition beyond the threshold.
The Policy Framework
Biodiversity Net Gain became a mandatory planning requirement under the Environment Act 2021, implemented from February 2024 for major developments and from November 2024 for smaller schemes. It requires applicants to use the DEFRA biodiversity metric to calculate baseline habitat value and demonstrate a minimum 10% net gain through on-site habitat creation, off-site credits, or statutory biodiversity credits (as a last resort).
What London's Data Shows
Across the first year of mandatory BNG, 86% of major London applications demonstrate compliance with the 10% minimum. The remaining 14% are a mixture of schemes in legitimate exemptions (brownfield land with very low baseline) and a small number of applications where the ecology assessment has not been completed to the required standard. The average BNG delivered across compliant schemes is 24% — suggesting that the 10% threshold is achievable without significant constraint on most development types.
“BNG has done something useful: it has forced developers to think about habitat at the start of the design process rather than bolting on a wildflower meadow at planning submission.”
— Senior ecologist, London Wildlife Trust, 2024
Urban Nature in the Pipeline
The most interesting pattern in the London data is the emergence of ambitious urban greening proposals that go beyond BNG compliance. Green roofs achieving 60%+ coverage, linear parks integrating planted biodiverse habitats, and habitat corridors connecting fragmented urban ecology are appearing in major applications with increasing frequency. The GLA's Urban Greening Factor policy has preceded BNG in establishing the London standard for habitat quality in new development.