Biodiversity Net Gain and Sustainable Development: What Ecological Land Management Has to Do With It

Biodiversity Net Gain became a mandatory requirement for most planning applications in England in February 2024. It’s been talked about for years – piloted, consulted on, delayed more than once – but it’s here now, and the development sector is working out what it means in practice. The headline is familiar enough: developments must achieve a measurable 10% net gain in biodiversity value compared to the pre-development baseline. What’s less well understood is the role that ecological land management plays in actually delivering that gain – not just on paper, but on the ground, over the 30 years the obligation runs for.

And that’s where a lot of the real complexity sits. Creating habitat is one thing. Ensuring it reaches and maintains the condition required to deliver the biodiversity units that were calculated at the planning stage is another thing entirely.

How the Metric Works and Why Management Is Central to It

Natural England’s biodiversity metric calculates habitat value using three variables: the area of habitat, its distinctiveness (based on the broad habitat type), and its condition. Condition is assessed against a defined set of criteria for each habitat type – things like species richness, sward structure for grassland, canopy cover and structural diversity for woodland, or water level regime for wetland.

Here’s the bit that matters for management: condition isn’t a fixed property of land. It changes depending on how the land is managed. A species-rich grassland managed incorrectly for two or three years can slip from good condition to moderate condition, losing biodiversity unit value in the process. Conversely, a poor condition grassland that receives appropriate management – correct cutting regime, removal of arisings, scrub control – can improve in condition over time, increasing its unit value.

So the management regime is baked into the metric outcome. Get the management right and the units are delivered. Get it wrong – or let it lapse – and the biodiversity gain that underpinned the planning consent starts to unravel. That’s a significant accountability mechanism. It’s also why the 30-year management commitment isn’t just a planning condition to be complied with minimally; it’s the thing that determines whether the BNG scheme actually works.

On-Site vs Off-Site Gain

BNG can be delivered on-site – within the development boundary – off-site through a registered biodiversity gain site elsewhere, or through statutory biodiversity credits purchased from Natural England as a last resort. The hierarchy is deliberate: on-site first, off-site if on-site isn’t sufficient or practical, statutory credits only where neither works.

On-site delivery is preferred because it integrates green infrastructure into the development itself – green roofs, ponds, species-rich planting, hedgerows, habitat corridors between green spaces. For residential developments, this has the added benefit of connecting residents to nature on their doorstep, which has its own wellbeing and community value beyond the ecological accounting.

Off-site gain is where larger-scale ecological land management comes in. A developer whose site can’t achieve the full 10% gain on-site can purchase biodiversity units from a registered off-site gain site – land that’s been assessed, had a management plan approved, and registered on the biodiversity gain site register. The landowner providing that off-site gain commits to the 30-year management obligation, and a conservation covenant or planning obligation secures that commitment legally.

The market for off-site biodiversity units is developing, and it’s an interesting one. Landowners with suitable land – typically lower-quality agricultural land with potential for habitat creation or restoration – can enter the market as biodiversity unit providers. The income from unit sales can be significant enough to make it a financially attractive alternative to continued agricultural production on marginal land. Whether that market develops as well as it should is partly a question of how the regulatory framework around unit verification and monitoring beds in over the next few years.

What Makes a Good BNG Management Plan

A Habitat Management and Monitoring Plan (HMMP) is required for all BNG schemes. It’s the document that sets out what habitats are being created or enhanced, how they’ll be managed, and how their condition will be monitored and reported. The quality of HMMPs varies considerably in practice – some are genuinely useful operational documents, others are aspirational statements with limited practical content.

A good HMMP covers the following, at minimum:

HMMP Element	What It Should Include
Habitat description and baseline	Current condition assessment, mapped habitat extents, species data from surveys
Management objectives	Target condition for each habitat, linked to metric condition criteria
Management prescriptions	Specific activities, timing, frequency, equipment, and responsible party
Monitoring protocol	Survey methods, frequency, condition criteria being assessed, reporting requirements
Adaptive management	How management will be adjusted if monitoring shows condition isn’t improving
Governance and responsibility	Who is responsible for management delivery, who holds the monitoring obligation
Funding mechanism	How management costs are funded over the 30-year period

The adaptive management element is one that I think deserves more attention than it usually gets. Habitats don’t always respond as predicted. Ground conditions, weather, grazing pressure, invasive species – any of these can push a site in an unexpected direction. An HMMP that has a clear process for identifying when targets aren’t being met and adjusting the management response is considerably more useful than one that simply prescribes a fixed regime and assumes it will work.

Ecological Land Management and Sustainable Development – Bigger Than BNG

BNG is the current policy headline, but the relationship between ecological land management and sustainable development goes beyond the mandatory 10% gain requirement. The Environment Act’s broader ambition – to halt the decline in species abundance by 2030 and achieve species recovery by 2042 – implies a much more fundamental shift in how land is managed across England as a whole.

Local Nature Recovery Strategies, being developed by each upper-tier local authority in England, are supposed to identify priority habitats and species at the local level and map the opportunities for nature recovery across the landscape. Development that aligns with those priorities – creating or enhancing habitats in locations identified as strategic for nature recovery – will deliver greater ecological value than development that simply meets the minimum BNG requirement in the least expensive way.

There’s a gap, currently, between the ambition of the Local Nature Recovery Strategies and the reality of how BNG decisions are being made on individual planning applications. Most developers are, reasonably enough, focused on meeting the mandatory requirement at acceptable cost. The bigger picture of how individual schemes contribute to landscape-scale nature recovery is a conversation that’s starting to happen but hasn’t fully landed yet in development practice.

Our ecological land management for biodiversity gains works across both scales – the site-level habitat management that delivers BNG units and the longer-term land stewardship that contributes to genuinely meaningful ecological recovery over time.

Protected Species and Designated Sites – An Additional Layer

BNG operates alongside – not instead of – the existing framework of protected species legislation and designated site protection. Development that affects a Site of Special Scientific Interest still requires Natural England consent. Great crested newts, bats, water voles, and other European Protected Species still require mitigation licensing under the Habitats Regulations. Ancient woodland still benefits from the strong presumption against development under the National Planning Policy Framework.

These protections are separate from BNG and aren’t satisfied by biodiversity unit calculations. A development that impacts a bat roost needs a licensed mitigation strategy regardless of whether it achieves 10% BNG. The two frameworks need to be managed in parallel, which adds to the ecological workload on complex sites but also means that the most sensitive features retain specific protection independent of the net gain accounting.

Worth knowing, because occasionally people assume BNG is a single mechanism that covers all ecological obligations. It isn’t. It covers habitat gain at the site level. Protected species, designated sites, and other ecological obligations sit alongside it and need separate attention.

Frequently Asked Questions

When did mandatory BNG come into force?

For most major and minor planning applications in England, mandatory 10% BNG came into force on 12 February 2024. Nationally Significant Infrastructure Projects were brought into scope from November 2025. Small sites (below the threshold for major development) and householder applications have different requirements. Permitted development rights are generally exempt, though this is an area of ongoing policy discussion.

Who verifies that biodiversity units are being delivered?

For on-site gain, the local planning authority holds the monitoring obligation and may carry out or commission condition assessments against the approved HMMP. For off-site gain sites, the responsible body holding the conservation covenant has a monitoring role, and local planning authorities retain oversight. In practice, monitoring capacity varies considerably between local authorities – it’s an area where the system is still developing its infrastructure.

Can BNG requirements be met by paying a financial contribution rather than creating habitat?

Only through statutory biodiversity credits – units sold by Natural England at a set price, as a last resort where on-site and off-site delivery isn’t sufficient or practical. Credits are priced to be deliberately expensive compared to off-site habitat creation, to incentivise actual habitat delivery rather than payment in lieu. They fund habitat creation by Natural England rather than providing a get-out from the ecological obligation.

Does BNG apply to development on brownfield land?

Yes, with some nuance. The BNG metric calculates gains against the pre-development baseline – so brownfield land with little or no ecological value has a low baseline, meaning even modest habitat creation on-site can achieve 10% gain relatively easily. Brownfield sites with higher ecological value – open mosaic habitats on previously developed land, for instance, which are a Priority Habitat – require more careful assessment. Open mosaic habitat on brownfield is actually quite ecologically important and the metric values it accordingly.

A Genuine Opportunity, If Taken Seriously

Biodiversity Net Gain is an imperfect policy instrument. The metric has limitations. The monitoring infrastructure is still being built. The market for off-site units is nascent. And 10% is a modest ambition given the scale of biodiversity decline in the UK over recent decades.

But. It does establish, for the first time, a legally enforceable requirement that development leaves nature better off than it found it – backed by a 30-year management commitment and an accountability mechanism that didn’t exist before. That’s a meaningful shift in how development and nature relate to each other in England.

Whether it delivers on its potential depends enormously on the quality of ecological land management that underpins it. Well-managed habitat that genuinely improves in condition over the management period will produce real ecological value. Poorly managed habitat that degrades from its baseline condition will produce a paper gain and a real-world loss. The difference between those two outcomes is the quality of the management – and the seriousness with which the obligation is treated from day one.

That, more than anything else, is what determines whether BNG is a genuine contribution to sustainable development or just another box to tick on the way to planning consent.