Biodiversity Net Gain: a look at this emerging policy
A Policy with Promise — and Pitfalls
Biodiversity Net Gain (known as BNG) is an emerging policy and a system now legally required in England for most new developments. While BNG has been heralded by developers and environmentalists alike as a progressive planning tool, it would seem it is not all it’s cracked up to be with this poorly prepared system and local Councils in particular, unable to deliver its lofty promises.
What Sounds Like a Win-Win
At face value, BNG sounds like a win-win situation. New developments must leave biodiversity in a measurably better state than before. That could mean planting more trees, restoring wildflower meadows, or protecting endangered habitats. The goal is a 10% net gain in biodiversity, although some plans promise figures such as 20%! However, the implementation of this policy is riddled with gaps, loopholes and misplaced optimism.
From Theory to Troubled Practice
Whilst the principle behind BNG is solid, its execution is floundering. A recent survey cited that just 10% of Planning Consultants believe the system is working well. This is particularly alarming given how quickly BNG has moved from concept to legal requirement. Most concerning of all: nearly 40% of local planning authorities lack in-house ecologists, meaning they often cannot properly assess or enforce BNG plans. This has real-world consequences. Developers may use off the shelf metrics and off-site credits to tick boxes without actually delivering meaningful gains where they matter most. One of the recurring points is that the biodiversity metric used to measure gain is often misunderstood or misapplied, especially on smaller sites or those managed by ill-equipped local authorities. As Julian Arthur of the Chartered Institute of Ecology and Environmental Management warns. “It’s not just about numbers—it’s about ecological function”
Chelmsford’s Challenge: Hammonds Farm
All of this is critically relevant to residents of Chelmsford facing the proposed huge Hammonds Farm residential and commercial development. If BNG is to be the standard by which environmental protection is judged, then we must ask: who is judging, and how equipped are they? With Chelmsford City Council among the many local authorities stretched for ecological expertise, can we really trust that the biodiversity claims associated with Hammonds Farm will be properly assessed, implemented, and monitored? Furthermore, the scale of the Hammonds Farm proposal as part of Chelmsford City Council’s Local Plan brings additional complications. While BNG policies may be easier to manage on smaller developments, large-scale schemes like this raise concerns about habitat fragmentation, landscape-scale degradation and the long-term viability of offset sites, especially if they lie far from the impacted area. “Net gain should be local,” emphasises Helen Nyul of the Nature Positive Initiative but in practice, developers may opt to ‘offset’ biodiversity loss in entirely different regions. This is very troubling
Follow the Money: Who Really Benefits?
Another concern is the growing role of private firms in managing BNG credits and mitigation schemes. Instead of local Councils or conservation charities overseeing habitat enhancement, management companies may be brought in, raising concerns about transparency, profit motives, and long-term stewardship. Nina Pindham, a Planning Barrister warns that in the absence of clear legal responsibilities and enforceable standards, communities may be left with little recourse if biodiversity promises are broken.
A Call for Caution — and Clarity
For those of us opposing the Hammonds Farm development, this serves as a timely reminder not to be placated by green-sounding buzzwords or glossy environmental pledges. BNG is certainly not a silver bullet. Without local expertise, clear accountability, and robust enforcement, BNG risks becoming a fig leaf for damaging development: one that appears to improve the environment while actually eroding it.
Our beautiful area deserves more than numbers on a spreadsheet and in a Local Plan, we deserve real nature, near our homes, protected by policies that work in practice—not just in theory.
References
- CIEEM – Chartered Institute of Ecology and Environmental Management
- Nature Positive Initiative – Helen Nyul
- The Guardian – Biodiversity Net Gain Coverage
- Imvelo Ltd – Biodiversity Net Gain Explained
- Natural England (2019) – Biodiversity Offset Site Study
- State of Nature Report 2023 – RSPB, Wildlife Trusts, National Trust
- Chelmsford Local Plan Documents
- Duty to Cooperate – Planning Power Unpacked
- Hammonds Farm and Pigeon – General Progress Update
- A Landscape Under Threat – Truth Behind the Plan
- The Garden City Illusion – Developer Incentive Analysis
