Ensuring the co-existence of BNG and successful infrastructure projects

Biodiversity Net Gain, infrastructure projects,
© Ivan Kruk

David West, associate ecologist at Tetra Tech, explores the need to ensure a harmonious co-existence of Biodiversity Net Gain and infrastructure projects

There is an increasing focus on achieving Biodiversity Net Gain (BNG) as part of development, with it forming an important part of the forthcoming Environment Bill. Although this will make it a mandatory requirement for development, the National Planning Policy Framework already requires development to achieve net gains for biodiversity.

In advance of the Bill becoming law, many planning authorities are already making BNG a requirement through local plans, including setting minimum requirements, with 10% expected to be the minimum required under the Bill. Therefore, an understanding of BNG, how it is calculated and how it affects projects, is vital to those working in planning and development and no longer just applies to ecologists.

Projects achieving BNG are those that leave biodiversity in a better state then before, in accordance with 10 key principles. In practice, it involves using a metric-based methodology to calculate biodiversity units pre and post-development, taking into account impacts and proposed habitat creation to determine the change.

Achieving BNG

Whilst this promises to present a wealth of opportunities for wildlife and nature, it does come with its challenges for developers. Achieving Biodiversity Net Gain can be difficult, particularly on smaller sites and where other concessions on developable areas are already required to meet wider planning requirements. Flood storage capacity, public open space, community infrastructure and parking are just some examples, each of which come with their own space and resource requirements. Linear infrastructure projects may also be challenging due to additional impacts such as severance of habitat corridors.

One way in which BNG can be achieved is through creation of new habitats off site, to compensate for losses or impacts from development. However, there are also opportunities to integrate BNG into development. For example, SuDS provide an opportunity to deliver biodiverse wetland habitats alongside surface water treatment and management. The commitment to achieve BNG therefore puts a renewed emphasis on the need for ecologists to work together with wider disciplines to create efficient and multifunctional spaces that complement the built environment and deliver across a range of policy agendas.

Benefits of Regulation

One of the key benefits of the Environment Bill for the industry is the establishment of a consistent regulatory framework for BNG. At present, approaches are not consistent across local authorities or other decision-makers, which is challenging for project teams. Not only are targets inconsistent, but so are the methodologies required and interpretation.

The setting out of a standard requirement to be achieved will make project planning easier, and create a more level playing field. The former is vital, as one of the keys to successfully achieving BNG is to consider it as early as possible within the project lifecycle, and will allow planners and developers to take centre stage in nurturing and protecting the UK’s wildlife.

Another benefit will be the wider development of strategic compensation schemes, such as that in use in Warwickshire, Coventry and Solihull. These schemes identify suitable areas for habitat creation that can then be delivered by developer funding, where projects are unable to achieve BNG. An established pricing structure for credits will help with viability studies, where at present bespoke off-site compensation schemes may be required. There is also the potential for this approach to be more beneficial for biodiversity, as funding can be targeted at key areas such as ecological network opportunities. It also has the benefit of cleanly integrating with local plans, and avoids the potential for ransom scenarios or costly land acquisition.

What’s more, developers actually have much to gain from restoring ecological value to their sites from a commercial perspective, as enhancing the area’s green credentials is far more likely to draw attention from increasing numbers of ESG investors.

When to consider Biodiversity

The best chance of successfully achieving BNG is by considering biodiversity as early as possible in a project, such as site selection. Avoiding losses of high distinctiveness or irreplaceable habitats – such as lowland meadows or ancient woodlands –  is not only important for biodiversity, but impacts on these habitats will make it difficult, time consuming and costly – if not impossible – to achieve BNG. Therefore, an early assessment of the site baseline is vital for planning projects and feeding into layouts or design. Once this is complete, targets for BNG should be set, which can feed into further planning stages and disciplines such as green and blue infrastructure.

However, BNG is not the only reason biodiversity should be an early consideration. Most protected species have restricted survey periods; for example, the core survey period for roosting bats runs from May to August. Some projects also require several years of data, as is the case on the south coast, where three years of overwintering bird surveys can be required for sensitive sites. Missing these windows can lead to costly delays in project planning and delivery.

Data in BNG

The use of a metric-based approach to BNG makes it a quantitative process, where traditional ecological work has been largely qualitative, though the assessment of habitat condition in particular does still require professional judgement. In my experience, the best way of collating data at each stage of the BNG process is within a GIS database, making the management of biodiversity within a project more akin to asset management. One of the benefits of this approach is in long-term management. The use of a series of criteria for condition assessment enables clear management objectives to be set, and progress to be measured and tracked within the database.

One of the biggest challenges with BNG is the need for constant revisions, for example due to changes in layout. Because the metric is based on accurate habitat area measurements, this can lead to time-consuming and costly amendments, with even minor changes potentially impacting on the ability of projects to achieve BNG objectives. As a result, several GIS tools are being developed which, along with the use of databases and pivot tables, enable us to minimise these impacts.

Early consideration

With BNG to become mandatory, many developments will most probably require increased amounts of habitat creation. However, there are other land use requirements for development such as drainage and open space which, with appropriate design, can provide valuable contributions to achieve BNG. It is therefore vital that biodiversity is considered as early as possible in the planning process, and that ecologists work closely with other disciplines to achieve the best all-round outcome.


David West

Associate ecologist

Tetra Tech*

LinkedIn: Tetra Tech

Twitter: @tetratech


*As of 11 January 2021, WYG officially adopted the name of its parent company Tetra Tech.



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