Biodiversity Net Gain: Should the UK Prioritise On-Site Delivery or a More Strategic Off-Site Approach?

In practice, however, the implementation of BNG is proving considerably more complex.

One of the most significant debates emerging across the development industry, local authorities and environmental sector is whether BNG should be prioritised on-site within development boundaries, or whether greater flexibility should be afforded to strategic off-site delivery.

At face value, on-site provision appears the more attractive proposition. Integrating habitat creation into development schemes aligns with wider placemaking objectives, visibly demonstrates environmental enhancement and can contribute positively to green infrastructure networks. Yet as schemes move through planning and viability processes, a growing number of tensions are becoming apparent — particularly in relation to housing delivery, affordability and long-term management.

The reality is that there is unlikely to be a universally correct answer. Instead, the planning system may need to adopt a more nuanced understanding of where on-site BNG genuinely delivers the best outcomes, and where off-site provision may ultimately represent a more sustainable and effective solution.

 

The Case for On-Site BNG

There are clear advantages to integrating biodiversity enhancements within development sites wherever feasible.

Well-designed on-site habitats can improve visual amenity and placemaking, deliver accessible green infrastructure, enhance health and wellbeing outcomes, strengthen ecological connectivity locally and help embed nature recovery into everyday environments.

For local communities, on-site BNG can provide a visible demonstration that development is contributing positively to the environment, rather than simply offsetting impacts elsewhere. It can also support broader local authority ambitions around climate resilience, urban greening and multifunctional landscapes.

In some cases, particularly lower-density greenfield schemes or strategic urban extensions, on-site habitat creation can be integrated relatively successfully into wider landscape frameworks, drainage corridors and open space strategies.

Importantly, the mitigation hierarchy still rightly places emphasis on avoiding harm and enhancing biodiversity as close as possible to the impact location.

However, whilst the principle of on-site delivery is compelling, the practical implications are becoming increasingly difficult to ignore.

 

The Growing Challenges of On-Site Delivery

For many residential developments, particularly in constrained urban environments, delivering the full 10% BNG requirement on-site can come at a significant cost.

The most immediate issue is land take, as habitat creation areas inevitably occupy land that might otherwise accommodate housing, infrastructure or community facilities. On strategic sites this can materially reduce housing yield, whilst on smaller or brownfield schemes it can fundamentally compromise efficient site design.

This creates an increasingly difficult balancing exercise for planning authorities and developers alike. For instance, should scarce development land be prioritised for housing delivery or should larger proportions of sites be reserved for ecological enhancement?

The tension becomes even more pronounced against the backdrop of the Government’s continued focus on accelerating housing delivery and addressing affordability pressures.

In viability terms, the implications are equally significant. On-site BNG can reduce development value through loss of developable plots and the increased landscaping and ecological costs associated with habitat establishment requirements and long-term monitoring and management commitments.

For schemes already absorbing rising construction costs, affordable housing requirements and infrastructure contributions, alongside other potential implications relating to SANG or nutrient neutrality (in certain areas) the cumulative burden can become substantial, resulting in fewer affordable homes, delayed delivery or schemes becoming unviable altogether.

 

The Emerging Service Charge Debate

One of the less discussed, but increasingly contentious, consequences of on-site BNG is the issue of long-term management and maintenance.

Because BNG habitats must typically be secured for a minimum of 30 years, developers often establish private management companies to oversee ecological land, monitoring and maintenance obligations. These associated costs are frequently passed on to residents through estate service charges, which raises important questions around fairness and affordability. As scrutiny of residential estate charges increases nationally, this issue is likely to become more prominent within future planning debates.

 

The Argument for Strategic Off-Site BNG

Against this backdrop, it is important that within the sector we advocate for a more flexible and strategic approach to off-site BNG delivery. Critically, off-site provision does not necessarily mean inferior environmental outcomes. In fact, in many cases the opposite may be true.

Large-scale habitat creation delivered through habitat banks or strategic landholdings can provide better ecological connectivity and larger and more resilient habitats with reduced recreational disturbance, which in turn provide greater opportunities for nature recovery.

By contrast, small fragmented habitat pockets embedded within residential layouts may struggle to function effectively ecologically due to lighting, domestic activity, pets and ongoing human pressure.

There is also a strong argument that off-site BNG can better align with broader Nature Recovery Network objectives by concentrating enhancements in locations where they provide the greatest strategic ecological benefit.

From a development perspective, off-site delivery will also optimise housing capacity and scheme viability, helping to support affordable housing delivery and reducing the long-term maintenance (and service cost) liabilities. For many urban and brownfield developments, it may represent the only realistic route to achieving policy-compliant development whilst still delivering wider social and economic objectives.

 

The Risk of a Binary Debate

Perhaps the greatest risk is that the industry frames the discussion too simplistically, as though on-site BNG is inherently “good” and off-site provision represents a weaker fallback option. The reality is that poorly designed on-site habitats may deliver limited ecological value whilst constraining sustainable development objectives. Against this, however, poorly located off-site provision risks becoming disconnected from local communities and impacts, meaning it is key to provide effective outcomes through negotiation to ensure that meaningful on-site enhancement is incorporated wherever practical and development design genuinely responds to ecological opportunities, but flexibility remains for strategic off-site delivery where this achieves superior overall environmental and planning outcomes.

Importantly, the planning system has always been about balancing competing objectives. Biodiversity enhancement is clearly critical, but so too are housing delivery, affordability, viability and sustainable growth.

The challenge for policymakers, local authorities and developers is therefore not simply how to maximise BNG provision within red line boundaries, but how to secure the most effective long-term outcomes for both people and nature.