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Biodiversity Net Gain

Biodiversity Net Gain

The term ‘Biodiversity Net Gain’ (BNG) has been used increasingly in relation to construction projects over the last few years. Many local authorities have included a requirement for BNG in their planning policies for some time, but the passing of the Environment Act in November 2021 means that in England BNG is now even more important. Following a two-year transition period, from 12th February 2024 it will be mandatory for all new larger developments (with a small number of exceptions) to ensure a minimum 10% gain in biodiversity. This amends the Town and Country Planning Act 1990. Small developments, classed as either under 0.5 hectares in area or of less than 10 dwellings, follow suit in April 2024.

Similar rules came into effect in Wales in October 2023. It is likely that BNG requirements will also be introduced in Scotland in the next year or two.

But what does Biodiversity Net Gain actually mean and how is the situation changing?

What Is Biodiversity Net Gain?

BNG essentially means that developments should aim to leave the natural environment in a better state than it was before the work. Not only should there be mitigation for any losses to biodiversity caused by a development, but there should be improvements to enhance onsite diversity. In the past, an ecologist would use their professional judgement to assess whether a site had achieved this.

The Situation in England

Although biodiversity gains were already necessary through the National Planning Policy Framework (NPPF), the new Environment Act sets out more specific requirements in relation to BNG. As mentioned above, the Act specifies that there must be a minimum of 10% BNG for larger developments from February 2024. It will apply to small sites of under 0.5 hectares and one to nine residential dwellings from April 2024. Certain developments will be exempt, however. There is provision within the Act for this percentage to change in the future if deemed necessary. Local authorities can also vary the percentage upwards.

In addition, biodiversity gain must be calculated using the Defra Biodiversity Metric. This means it will no longer be down to an ecologist’s individual judgement to assess any gains.

The Act also requires a site to secure gains for a fixed period through planning regulations and conservation covenants between the local authority and developer. Currently, this period is set at 30 years, but, as with the percentage gain figure, there is provision within the Act for this to change.

If the 10% gain cannot be made onsite, then the developers will have to contribute to Local Nature Recovery Strategies (LNRS), to be identified by local authorities. Sites receiving these contributions will have to be on the national register of off-site net gain locations. And, if there are no suitable strategies local to the project, developers will be able to buy ‘biodiversity credits’ to invest in nationally strategic habitats instead.

Biodiversity Net Gain

Within this, there is an acknowledgement that some habitat types, such as blanket bog, are irreplaceable and removal cannot be compensated for via offsetting.

The Situation in Wales

In Wales, new rules on biodiversity gain came into effect in October 2023, although the term Net Benefit for Biodiversity (NBB) is used instead of BNG. The approach is similar to that now mandated in England, but the system does not use a statutory metric and there is no set minimum of biodiversity gain. Instead, enhancement is judged in relation to the size and nature of each development. To assist developers, Natural Resources Wales have created the DECCA Framework to help assess ecosystem resilience, a key factor in judging NBB. Full details of Welsh Government NBB rules and how they relate to the planning process can be found here.

Measuring Biodiversity Net Gain

Biodiversity is increasingly measured by calculating and assigning a unit value to a site’s habitat/s using a metric (or ‘tool’). Value is dependent on the type, size, condition, uniqueness and connectivity of a habitat, all elements that affect biodiversity. In this way, comparisons can be made before and after development. They are generally carried out by experienced ecologists.

Whereas habitat assessments have been a common feature of planning for a long time, metrics use a more specific set of criteria in their measurements. In England, the Environment Act makes it obligatory to use Defra’s Biodiversity Metric tool to calculate changes in biodiversity rather than any other metrics that have been in use previously.

It should be remembered that BNG assessment focuses on habitats as a measure of biodiversity. While protected species are part of this assessment, they will usually still need to be surveyed for separately and will still be covered by separate legislation.

Biodiversity Net Gains

Going Forward

In the UK, commitments to Biodiversity Net Gain have been a feature of the environmental policies of some companies and local authorities for some time. However, the passing of the Environment Act in England means that after a two-year transition period, the vast majority of developments are now mandated to increase biodiversity either onsite, or elsewhere locally, by at least 10%. If neither of these is an option, then biodiversity credits can be purchased to offset elsewhere.

In Scotland, the situation is likely to be similar before too long, although there have been delays to an update to the Scottish National Planning Framework. Because of landscape differences in Scotland, there may be a slightly different approach to England. For example, one challenge Scotland faces is the amount of irreplaceable blanket bog it holds and its desirability for wind farm sites.

This post is an updated version of one that originally appeared on this site in June 2022.