alen karso u0LpZFgbn1Q unsplash aspect ratio 1200 600

Delivering BNG: Keith Ross and Andy Bascombe on the challenges of Biodiversity Net Gain

Biodiversity Net Gain (BNG) is a legally binding commitment to leaving nature in a better state after development than it was before. Mandated by the Environment Act 2021 in England, BNG requires developers to demonstrate a measurable 10% gain in biodiversity. But as with any regulation, its practical application comes with complexities and challenges.

To shed light on the principles, benefits, and pitfalls of BNG, we spoke to two of APEM Group’s experts: Keith Ross (Divisional Director for Terrestrial Ecology, APEM Group), and Andy Bascombe, (Technical Director at Aspect Ecology, part of APEM Group). Drawing on their extensive experience, Keith and Andy discuss how BNG is impacting the development landscape, what it means for biodiversity, and how APEM Group works with clients to navigate the regulatory framework while delivering pragmatic, nature-positive outcomes.

Can you explain Biodiversity Net Gain (BNG) and why it’s important in today’s environmental landscape?

Andy Bascombe (AB): BNG was originally conceived as a mechanism to ensure that any development delivers measurable gains in biodiversity – it’s there to ensure a positive outcome for biodiversity – not just avoiding harm to the natural environment, but actively improving it.

So now, developers in England are legally obliged to deliver a 10% gain in biodiversity, which is measured using a Statutory Metric and provided to Local Planning Authorities when any Planning Application is made.

But there’s complexity in that BNG is not a single measurement – there are three different categories of habitat considered. So, there are Area Habitats, Hedgerow Habitats and Watercourse Habitats – which are all considered separately and the +10% BNG must be achieved for each of these independently of each other.

Keith Ross (KR): We should add that instead of looking at the presence of different species, BNG focuses on the extent and condition of habitats as a proxy for biodiversity, not an accurate measure of it.

So it only considers habitats, not species.

BNG doesn’t remove any obligation for mitigation of impact on any particular species – so if a planned development would adversely affect bats, you’re still going to need to provide conservation measures to protect the bat population. And these mitigations can’t be considered as part of the BNG calculation – that’s just about replacing what was already there.

BNG is a measure to ensure we achieve an additional 10% of new or improved habitat, over and above that provided for by previous legislation.

Regulations across the UK (and around the world) differ. What are the main differences in approach by region?

AB: As far as I’m aware, BNG isn’t a legal requirement anywhere else in the world, other than in England – although it may be a requirement in Scotland soon. Wales has a broader approach to delivering biodiversity gains – and they look at it on a case-by-case basis, without any specific metric or target. It’s much more of a qualitative assessment.

Even in England there are some regional differences – for example Kent has a policy that targets an aspirational +20% BNG. And in London, they use an Urban Greening Framework to help achieve appropriate gains even where 10% BNG is extremely easy to deliver.

KR: Being a legal requirement in England means that minimum standards are consistent across all LPAs. That’s a good thing, in that before BNG, there were many different and inconsistent approaches between counties. But of course, as we’ve already touched on, there are a number of downsides too.

Keswick, Lake District, Cumbria, UK

So, what are the challenges of applying BNG in practice?

AB: The principles of BNG seem simple enough on the surface, but in practice it can be really complicated.

BNG applies different scores to habitats based on what is deemed to be their biodiversity value. Some score higher, and some score lower.

That’s fine in principle, but the way in which habitats are scored is can be questionable. For instance, scrubland scores higher than newly planted woodland because it reaches maturity faster. Woodlands take decades to reach their full ecological potential, which means their long-term contribution in terms of things like carbon storage or water management, are not accurately represented.

Another related issue is that BNG assigns higher scores to habitats that are deemed to have greater biodiversity value. When a site has lower-value habitats, the replacement habitats may also be of low value. It’s easy to achieve 10% when there was virtually no biodiversity in the first place, the issue being that in some cases, the money spent might achieve better biodiversity outcomes if it were used differently.

And if a development impacts a high-value habitat, the replacement or enhanced habitats required will be larger and more expensive to deliver. In that sense, BNG tends to protect the most valuable habitats because the cost of developing them is simply much higher.

But on the flip side, Brownfield sites are often high in biodiversity and score highly under the Metric. The costs associated with BNG compliance can actually discourage development on these sites in favour of agricultural land which scores lower for biodiversity – clearly this has implications for the protection of our countryside and even for our food security in the long run.

KR: Yes, so that’s an issue of unintended consequences. Developers face challenges in balancing the need for measurable outcomes with the financial realities of delivering complex projects. By inadvertently incentivising cheaper habitat options like scrub over longer-term investments like woodland, BNG may not end up delivering the ecological value it was intended for.

Another difficulty is the practical application of BNG for certain habitat types, particularly linear habitats like watercourses. Where a watercourse is within 10m of a site boundary, even if that watercourse is in someone else’s ownership, it must achieve the +10%. Negotiations can involve multiple landowners, and to make that even more challenging, the offsetting costs of watercourse BNG units can be very high.

It’s important that developers consider BNG early in the design stages because the costs associated with it may affect the viability of schemes, particularly where higher valued habitats are present.

Are there any other challenges to consider with the BNG Metric?

KR: As part of BNG, developers are obliged to manage any biodiversity enhancements they deliver for at least 30 years. Whilst that creates opportunities to be more strategic about long-term habitat management, it also adds another layer of complexity – and we’re concerned about the ability of local authorities to enforce these commitments, given their resources. I’m not sure it’s reasonable to expect LPAs to enforce monitoring and reporting for 30 years, for all developments.

AB: Yes, ensuring compliance over a 30-year period is definitely a huge challenge, but there’s no doubt that at some point there needs to be a way of checking that the plans we’re putting in place are having the desired impact. If in 10 years’ time, someone does an assessment and finds that the actions taken only delivered an average of 3% gain, then the entire process is undermined.

How do you see BNG evolving in the future?

KR: I think we’ll also see a greater focus on monitoring and enforcement. Ensuring that enhanced habitats deliver the intended benefits over 30 years will be critical, and this is an area where technology and innovation will play a key role. From habitat mapping to remote monitoring, there are opportunities to improve how BNG success is measured.

The issue will be whether BNG actually has the desired effect. The problem with the law is that it’s a very blunt instrument – there’s no room for nuance, but one thing we definitely understand about biodiversity is that it’s very nuanced. Whilst it’s good in some ways to have a standardised approach, we’ve lost some of that nuance. We’ve partly replaced expert opinion with a mathematical model that dictates what developers have to do, regardless of whether it’s ecologically the right thing to do.

AB: BNG is still in its early stages, and we’d hope to see refinements to the metric as it’s applied more widely. For instance, there’s an ongoing discussion about incorporating species considerations alongside habitats to create a more holistic approach. But as policies and practices evolve, we’ll continue to stay at the forefront, ensuring our advice is always aligned with the latest developments.

How does APEM Group support clients in delivering BNG effectively?

AB: We’ve mentioned the importance of incorporating BNG into the early stages of project design – we can provide valuable early-stage advice to help clients navigate the complexities of BNG. This includes conducting baseline assessments to understand the ecological value of a site, identifying opportunities for enhancement, and advising on how to integrate BNG into the design process. We aim to address risks early and provide practical solutions tailored to each project.

KR: Our expertise is key. Good ecological design, working closely with clients to ensure that their BNG strategies are both ecologically sound and financially viable. We know how to apply the principles and identify practical ways to modify projects to increase the likelihood of achieving +10% on site, which is almost always more cost-effective than offsite.

It’s a really complex area, but with our expertise, clients can navigate BNG with confidence, ensuring their projects achieve both commercial objectives and genuine biodiversity benefits.

If you would like to speak with the team regarding Biodiversity Net Gain, please contact us.

Related Articles

Biodiversity: the foundation for all our futures

Biodiversity refers to the variety of life on Earth, encompassing all species of plants, animals, and microorganisms, as well as...

Read More
Jo James by a river

Biodiversity monitoring using environmental DNA (eDNA) in still waters

Biodiversity assessments enable industries to understand their impact on the environment and how they can minimise and mitigate this effect....

Read More
APEM Group ESG Report cover

Read the APEM Group ESG Impact Report

Environmental considerations have always been at APEM’s core, from our inception in 1987 to becoming a global environmental consultancy group...

Read More