Quick-Fire Biodiversity Net Gain Q&A

Your Top Biodiversity Net Gain FAQs and Our Simple, Straightforward Answers

At first glance, the prospect of mandatory biodiversity net gain (BNG) may seem daunting, but as it will affect a significant percentage of development work and planning condition applications moving forward, it is crucial that developers harness a knowledge of it. If you have any questions about the mandate, our BNG plans or any topics that relate to the planning policy, we are experts and want to help developers and other key stakeholders to understand it better and implement it within their demolition, design or construction project accordingly.

Throughout this page, you will find answers to frequently asked questions on biodiversity net gain and the integral part it plays in environmental management to enhance biodiversity, as well as the impact it is now likely to have on multiple developments for many developers across the nation. If, however, you are left with any unanswered questions, don’t hesitate to get in touch and one of our team will be happy to help you with your query.

What are the aims of biodiversity net gain?

In simple terms, the primary objective of mandatory biodiversity net gain (BNG) is to improve the state of the environment post-development compared to pre-development. Looking closer at the policy requirement, BNG provides numerous environmental benefits such as boosting air quality and water quality, fighting the effects of climate change, preserving ancient woodland and veteran trees, and saving potentially irreplaceable habitat sites and valuable plants from unnecessary destruction.

Even with restrictions over how a development proposal and the planning process are carried out, the government announced BNG to avoid needless harm to the environment over future developments in a way that will encourage developers to undertake their development project, but with sensible planning conditions that won’t treat local biodiversity and the current standard of biodiversity on a development site as collateral.

When was the concept of BNG first created?

Prior to Brexit, biodiversity in the UK was protected by the European Union through several pieces of existing legislation that ensured the laws were followed across the country, including the Conservation of Habitats and Species Regulations 2017, the Wildlife and Countryside Act 1981 and the Natural Environment and Rural Communities Act 2006. It was also a legacy policy within the National Planning Policy Framework (NPPF) 2012 (revised in 2018 and 2019) and local plans in countless locations.

After Brexit and as a method of establishing infrastructure that would guarantee an improvement to the environment following the completion of development and land management projects, biodiversity net gain was included as part of the new Environment Bill unveiled in the 2019 spring statement before becoming a law once the Environment Bill turned into the Environment Act.

When did biodiversity net gain become law?

The BNG planning policy was one of several components of the Environment Bill. In November 2021, the new Environment Bill gained royal assent, became the Environment Act and was passed into UK law as new legislation applicable to anyone looking to develop land in England. Due to a two-year transition period initiated by the UK government, however, biodiversity net gain wasn’t yet enforced and wouldn’t be until February 2024.

That said, in preparation for the policy becoming enforceable, many local planning authorities opted to demand a 10% increase for enhancing habitats and building the overall biodiversity value on development sites prior to the change. Considering the need to satisfy mandatory BNG, developers should start thinking about the environmental impact their proposed development could have on local ecological importance and present wildlife habitats before reaching out for new guidance on the planning requirement.

If BNG isn’t yet enforced, why are my local planning authority asking for it now?

Despite a two-year period of transition that was set to last until February 2024 (formerly November 2023 and January 2024), many local councils chose to insist on the rules of BNG being followed ahead of time. For example, Bristol City, Cornwall, Dorset, Leeds, Lichfield, Warwickshire County and Wiltshire all have their own local-level policies and methods that relate to BNG directly or, at least, the concept of suffering no net loss following the completion of a planning project. In Cornwall’s case, since 2020, all major planning applications have had to provide 10% net gains for biodiversity, and in Warwickshire’s case, they have their own biodiversity metric.

Once it was confirmed that it would definitely be coming, many councils across the country took the view that it was better to be overprepared than fail to deliver on day one. Many pilot projects were already undertaken or were underway to avoid ‘day one failure to deliver’ once BNG became law. As a result, developers were universally advised to follow the biodiversity net gain planning requirement in case their local planning authority was implementing the policy ahead of time.

Who regulates biodiversity net gain?

As with all national policy sets, the mandatory biodiversity net gain policy within the Environment Act is regulated by more than one responsible body. In this case, public bodies include the Department for Environment, Food and Rural Affairs (DEFRA) in accordance with Natural England / Natural Resources Wales (in England and Wales), the Natural Capital Committee (NCC), the British Standards Institute (BSI), Local Nature Recovery Strategies (LNRS), the Nature Recovery Network (NRN) and a limited number of other organisations.

Even before it originally became a mandatory requirement in November 2023 before eventually changing to January 2024 and then February 2024, BNG was already regulated by key stakeholders on behalf of a responsible body and local decision-makers, such as the corresponding local authority.

Why 10%?

Following a consultation in 2019, it was decided that 10% would be the mandatory minimum for a net gain of biodiversity. It is clearly an arbitrary figure, and as such, many experts believe that it could be adjusted in the future once it is possible to establish the long-term effectiveness of BNG in practice.

Local planning authorities are given the option of forcing an increase in biodiversity above 10% to 15% or even 20%. While a higher figure means further changes to development plans and a more difficult challenge to raise biodiversity value on the site and obtain planning permission, it doesn’t mean that different metrics will be used, and with the extensive experience of an ecological consultancy such as ours, the requirements of biodiversity net gain will still be met.

What is a biodiversity unit?

Also sometimes known as a biodiversity credit, a biodiversity unit is a minimum functional area of habitat such as woodland or hedgerow that qualifies through the biodiversity metric calculation as one complete unit. Units account for both habitat units and hedgerow units, and together, they account for net gains and losses to biodiversity on your development site.

As some sites are naturally more biodiverse than others, a smaller area on a particularly biodiverse site is often equivalent to a single unit. Likewise, a single unit may be calculated differently on a site with a poor condition of biodiversity.

How would you measure biodiversity value of a habitat?

During the biodiversity net gain assessment, further information regarding the site and all ecological features present will be collected to determine the relative value of each asset. Although every site is different and requires an approach that accounts for judging the habitat site on a case by case basis, all irreplaceable habitats will be judged in the same way, using the following factors to gauge local importance.

Factors used to evaluate the value of a habitat include the condition and quality of the habitat, the connectivity of the site and other areas, the ecological importance locally, the habitat’s distinctiveness, the habitat’s diversity and rarity, the habitat’s size, and the strategic significance of the site. BNG metrics will then be used to compile all of these variables and produce a habitat value, making it into a biodiversity unit that can be filtered into the overall effort to retain and boost biodiversity value.

What is the biodiversity metric?

Currently, the DEFRA biodiversity metric 4.0 is used for measuring biodiversity on a site, but it may change if a more effective way to calculate biodiversity net gain is identified in the future.

As with many components of BNG, the first few years of the policy are likely to act as a teething period and a trial-and-error opportunity to determine potentially more suitable solutions. That said, some local authorities have developed their own biodiversity metric and may therefore not be as inclined to keep tabs on future updates to the current biodiversity metric.

Why are there so many biodiversity metrics?

Various authorities across England are experimenting with their own biodiversity metric in an attempt to develop a method of calculating biodiversity net gain in a way that is suitable and effective for the areas within their jurisdiction.

In March 2023, however, DEFRA released an updated biodiversity metric known as biodiversity metric 4.0, as well as a small sites metric, with the intention of making it universal across all local councils.

What is a conservation covenant?

A form of existing legal protection over designated sites, conservation covenants are formed between responsible bodies and the developer or landowner to ensure protection over valuable rural areas and the biodiversity present. With tight restrictions in place, existing protections in the form of conservation covenants will remain active even if the landowner decides to sell or relinquish ownership of the plot of land.

The landowner can also benefit from initiating a conservation covenant in the right area, as it could lead to financial assistance, compensation or tax benefits if any development projects that could breach the covenant are undertaken on the site.

What are the BNG exemptions?

The results from a biodiversity net gain consultation in 2019 outlined the government response to the general public’s concerns over the BNG policy, including more detail on proposed exemptions. Within the consultation, named exemptions to the policy were brownfield sites under certain criteria, habitat sites, household applications, marine developments, Sites of Special Scientific Interest (SSSI), and the potential to include statutory protected sites.

Although not exempt, the consultation also stated that minor or small-scale development projects would undergo a simplified process.

What does the BNG assessment consist of?

Similar to a Preliminary Ecological Appraisal (PEA) except with integration of the DEFRA metric methodology to produce a calculation for biodiversity units, biodiversity net gain assessments involve a standard survey of priority habitats and legally protected species classed as relevant planning considerations.

Through measuring the pre-development biodiversity value before the project and the post-development score based on predicted biodiversity losses and gains after the project, negative impacts on the environment can be pinpointed. Using the calculations alone, further detail on the nature of the development will dictate a suitable biodiversity net gain approach to avoid impacts and meet the required increase, delivering biodiversity net gain on the site.

How does the mitigation hierarchy apply to biodiversity net gain?

During a BNG assessment, a successful net gain of biodiversity from the perspective of the ecologist undertaking the survey will require them to follow a universal suggested structure that ensures changes to the site to improve biodiversity are made and alterations that could harm the local environment are only initiated if it is absolutely necessary. The mitigation hierarchy enables an ecologist to make pragmatic solutions and prevent biodiversity loss on the site. Although often extended into further subcategories, it is often formed from the three primary levels of avoidance, mitigation and compensation.

In any situation, the top priority in the mitigation hierarchy would be to avoid natural assets on the site and allow them to retain their place. If the development makes this impossible, the ecologist will find mitigation measures that minimise impact. If, as a last resort, it isn’t possible to find a compromise, certain ecological assets may need to be destroyed or relocated away from the site. An example of this would be if certain habitat types on the site were obstructing the development or other issues such as invasive plant species would be likely to hinder the project or damage infrastructure.

The ecologist would then be tasked with leading an off-site habitat enhancement by forming a new habitat creation away from the site. A starting point in meeting the minimum requirement of retaining the same general condition of biodiversity on the site, the ecologist would then be able to determine great opportunities to make measurable improvements of at least 10% and meet the biodiversity gain requirement, either delivered on-site or using off-site compensation.

What happens if I cannot achieve an increase in biodiversity?

As an absolute last resort, our ecologists are able to offer the option of offsite compensation. If all methods of developing land in a way that can retain value and increase the number of natural habitats have been exhausted and it simply is not possible to achieve biodiversity net gain on the development site, the ecologist will look to initiate the 10% increase in other areas of the country through biodiversity offsetting.

Once the biodiversity metrics assign irreplaceable habitats with a unit value at the first instance, the biodiversity units can be bought from landowners as biodiversity credits. That way, the new development project increases biodiversity gains, except in another part of the country away from the chosen site, enhancing the country to a better state for at least 30 years as a whole rather than using one specific location.

How does biodiversity net gain affect planning decisions?

Local planning authorities across the country must enforce certain planning policies before granting a planning obligation. Along with arboricultural surveys, topographical surveys and ecology surveys such as a habitat survey, a biodiversity net gain assessment and the accompanying biodiversity net gain plan meet the requirements of the local council, making the decision to accept planning permission on the site seamless for local authorities.

Providing a trusted and reliable ecological consultancy has carried out an assessment to achieve biodiversity net gain and produced a report to secure measurable net gains on the site, the planning system of the local planning authority should allow planning consent without hesitation.

How much should I expect to pay for a BNG assessment?

For an average development site, the upfront ecological survey which is used to inform the scheme would likely cost somewhere between £500 and £1,000 excluding VAT.

The cost may be higher or lower for larger or smaller development sites. Overall, depending on the scale and uniqueness of your site, and the quantity and importance of nearby ecological receptors, the cost of BNG assessments can vary, with small private developments likely to cost less than large nationally significant infrastructure projects. With this in mind, it would be worthwhile to speak to us directly so we can give you an accurate quote based on your specifications.

What is included in a biodiversity net gain plan?

Straightforward and simple reports specifically produced for delivering net gain, our biodiversity net gain plans outline a full picture of the planning process for meeting the requirement. In essence, alongside general biodiversity net gain guidance, a BNG plan will include the number of statutory biodiversity credits needed to deliver net gain, the methods of reaching this target and making the necessary biodiversity improvements on-site or off-site, and further details into the timescale of how and when this will be carried out.

All three factors are incorporated at the report stage, as well as detailed guidance on implementing BNG, further details about our approach to deliver BNG, other courses of action designed to mandate net gains, and other information that could contribute to achieving planning permissions on the site through the corresponding local planning authorities.

How much does a BNG plan cost?

For the landowner, an off-site biodiversity management plan is typically around £1,000 excluding VAT. Once again, the cost of a BNG plan will vary based on the specifications of the site and project, often leading to the requirement for a bespoke quote. In the case of a BNG plan, the cost would also be impacted by the number of units needed to achieve BNG.

For the developer, on-site biodiversity net gain plans are typically priced between £500 to £1,000 excluding VAT. As with the cost of biodiversity net gain assessments, the price is likely to vary depending on the size of the site, the intricacy of your scheme, and the number of units needed to achieve a net gain of 10% and find success in delivering BNG.

How much do the legal fees associated with biodiversity net gain cost?

If it is not possible to deliver biodiversity net gain on the site and biodiversity units need to be purchased off-site, the cost of this expense could vary significantly. Biodiversity credits bought from the local planning authority can cost anywhere between a few hundred pounds to several thousands of pounds, with the deciding factor typically being the amount of land falling short in the policy requirement and the number of units required outside of the site.

The legal agreement for the landowner to reach the 10% biodiversity net gain requirement and ensure it is secured for over 30 years could cost around £10,000 including a contribution to the legal fees of the local authority and, in some cases, the legal fees of the developer.

How long does it take to produce a biodiversity net gain plan?

It doesn’t take long at all for one of our ecologists to complete and send across your completed BNG plan. As soon as the necessary assessments have been carried out, the ecologist will begin to produce the BNG plan and you should receive it within a few short days of the site visit.

You can then submit it to your local planning authority to prove that you’ve received expert advice on your site, detail how you will leave the site in a measurably better state post-development for at least 30 years, and act as strong support for a planning application.