It’s now been just over a year since Biodiversity Net Gain (BNG) became mandatory under the Environment Act 2021, requiring most developments to deliver a 10% net improvement in biodiversity. Our assistant director and head of planning and architecture, Natasha Blackmore da Silva shares her thoughts.
From my perspective working in planning, it’s been a bit of a mixed bag — promising in principle, but patchy in practice.
BNG was broadly welcomed when it first came in. The idea of integrating nature into development is something many of us support, and having a clear 10% target has helped bring planning, design and ecology teams together earlier in the process. I’ve seen firsthand how that kind of collaboration can lead to better outcomes.
But as with many new policies, the reality has been more complex. Local planning authorities simply weren’t ready for BNG.
Many still don’t have in-house ecologists or enough resources to properly assess developments incorporating BNG, which causes long delays — even on relatively straightforward applications. What used to be an eight-week turnaround is now regularly stretching to four months or more.
In my own work, I’ve had projects where we could achieve the 10% uplift on-site and in those cases, things have moved smoothly.
But where off-site provision is needed, things get much harder. I’ve had small schemes—three units, for example—where only a 4% gain was possible on-site.
It took months of back and forth with ecologists exploring every option before the client ended up proposing to buy BNG credits, prior to the application even being submitted.
At Sheldon Bosley Knight, we’ve worked closely with ecologists to navigate the metric system and secure off-site solutions for clients when needed. But uncertainty around how different local planning authorities interpret and enforce BNG requirements continues to cause issues.
Some authorities want conditions, others insist on legal agreements and there’s little consistency even within the same council.
I believe the current approach, especially for smaller sites, just isn’t sustainable. Trying to deliver 10% BNG alongside affordable housing contributions and Community Infrastructure Levy (CIL) payments is making some small developments unviable.
Often, what gets delivered are awkward pockets of green space on site edges that are marginal, difficult to maintain and don’t offer real ecological value in the longer term.
Moving forward, I’d like to see a more flexible, tiered system. Something similar to CIL — a set fee per unit or square metre that developers can pay, allowing local authorities to deliver larger, high-quality, strategic habitats off-site.
This would not only be more practical, but also more effective for biodiversity in the long term as it would support the creation of habitats that will over time will become self-sustaining.
BNG has huge potential, but to really make it work, we need more support for councils, clearer national guidance, and a system that reflects the realities of development on the ground — not just the ideals.
Visit our YouTube channel here to see Natasha explain more about BNG on our latest podcast.
If you would like expert planning advice, please contact Natasha or one of her team on 01789 387887.
