Why biodiversity net gain is a strategic asset for major infrastructure projects

Stacking is key to derisking BNG on major infrastructure projects

Getting biodiversity net gain (BNG) right for major infrastructure projects is about more than meeting a metric. As BNG becomes mandatory for Nationally Significant Infrastructure Projects (NSIPs) in November 2026, project promoters must demonstrate not only compliance, but credible, deliverable and long‑term outcomes. One approach already embedded in policy, but still underused in practice, has the potential to transform how BNG is delivered at scale: stacking.

BNG stacking treats habitat creation and enhancement as a staged, long‑term process rather than a one‑off intervention. By planning sequential improvements over time, stacking aligns infrastructure delivery with natural ecological processes, while unlocking programme, consenting and commercial value. For NSIPs, where land requirements, delivery risk and examination scrutiny are particularly acute, this approach can reposition BNG as a strategic asset rather than a late‑stage constraint.

BNG’s evolution from aspiration to obligation

It is striking to see how a once voluntary aspiration of BNG has evolved into a defining feature of England’s planning system. The UK’s good practice principles for BNG, which were published 10 years ago, require development to leave biodiversity in a measurably better state than before. In practice, this applies across a wide range of development types, from railways, reservoirs and substations to major housing schemes, with impacts avoided and minimised and new habitats created and enhanced to support nature’s recovery.

BNG has been mandatory for most planning applications since 2024 and extending the requirement to NSIPs, will mark a significant shift for the country’s most complex and ambitious schemes. For organisations involved in major infrastructure delivery, the scale of this change is front of mind. Many are grappling with the challenge of applying the biodiversity metric across extensive landholdings, securing suitably located land for biodiversity gain and committing to long‑term management obligations that extend for at least 30 years.

At the same time, experience across the sector increasingly shows that BNG cannot be treated as an afterthought. For NSIPs, robust and well‑evidenced approaches will be essential to secure consent and deliver benefits for nature and communities, both locally and at scale. With two years of mandatory implementation outside of the NSIP process now completed, attention is turning toward approaches that can unlock longer‑term strategic value. BNG stacking is one such approach.

How stacking adds real value

Stacking can be the combining of multiple environmental benefits. In this context, however, it refers to a long‑term, sequential approach to habitat enhancement that reflects how ecosystems develop over time.

When habitats are created or restored, nature does not remain static. A species‑rich grassland may progress to scrub, then woodland and, over time, support highly valuable features such as veteran trees. Stacking recognises this ecological succession and plans intentionally for how habitats will change over decades, rather than attempting to realise a final outcome in a single intervention and in a single timeframe.

In practical terms, stacking involves creating and enhancing habitats in stages. For example, a site that begins as modified grassland in poor condition might first be improved to neutral grassland in moderate condition, secured through a long‑term management agreement and generating biodiversity units. Once that target habitat and condition is achieved, the habitat becomes the baseline for a further stack of enhancement, potentially progressing toward good‑condition grassland and, in time, lowland meadow.

This incremental approach mirrors natural processes and creates a more realistic, lower‑risk pathway toward habitats that are otherwise difficult, costly or uncertain to establish in one step.

Why stacking expands what is possible

By aligning with ecological succession, stacking reduces delivery risk and supports healthier, more resilient ecosystems. It also introduces regular points of value over time, benefiting both NSIP developers and BNG providers as each enhancement stage builds on previous progress.

Stacking also reshapes the economics of BNG delivery. High‑value habitats are challenging to create directly from low‑value baselines, reflected in higher risk multipliers within the biodiversity metric. Delivered through stacking, these habitats become more viable, with investment spread over time and risk reduced at each stage.

For NSIPs, stacking helps address one of the most persistent challenges in BNG delivery: land availability. By maximising biodiversity units per hectare through long‑term planning, projects can minimise the amount of land needed, while still delivering meaningful biodiversity outcomes. For landowners and managers of BNG sites, stacking provides a structured route to long‑term stewardship, underpinned by recurring value across enhancement stages.

Creating early value for infrastructure providers

For infrastructure owners responsible for delivering NSIPs through the Development Consent Order (DCO) process, stacking within BNG offers benefits that go beyond basic compliance. Applied strategically, it can generate programme certainty, support consenting and improve commercial outcomes across the project lifecycle.

By investing in an initial BNG stack ahead of DCO consent, infrastructure organisations can demonstrate early and credible delivery of biodiversity enhancements during examination. This gives examining authorities and statutory consultees confidence that BNG commitments are deliverable in practice, rather than theoretical obligations deferred until after consent. In turn, this can help reduce perceived delivery risk and support a more constructive examination process.

Early stacking also enables meaningful engagement with key stakeholders, including BNG providers, landowners and local authorities. This early engagement helps to clarify land availability, address trading rule constraints and establish long‑term management arrangements in advance of construction. Crucially, it allows some of the most challenging elements of BNG delivery to be de‑risked at an earlier stage in the programme.

Once DCO consent is secured, investment in subsequent BNG stacks becomes a stronger commercial proposition. Where early habitat creation or enhancement has already begun, projects may benefit from “early BNG”, which is recognised within the biodiversity metric. This can reduce the total number of units required to achieve the mandatory 10% uplift, improving overall efficiency and value for money.

Taken together, this staged approach helps position BNG as a strategic asset that supports delivery, regulator confidence and stakeholder relationships, rather than as a compliance cost incurred late in the process.

A turning point for BNG

As BNG becomes mandatory for NSIPs, the focus is moving beyond understanding the metric to designing deliverable, long‑term solutions that balance ecological and economic considerations. Experience increasingly shows that no single discipline can deliver this in isolation. Successful implementation depends on integrating ecological insight, planning strategy, environmental assessment and economic analysis from an early stage.

Within this context, BNG stacking stands out as a practical and strategic tool. Embedded early and applied in phases across the project lifecycle, it helps organisations responsible for delivering major national projects address risk, secure land and management arrangements with confidence. In doing so, it supports the delivery of biodiversity outcomes that are credible, cost‑effective and aligned with natural processes.