Biodiversity Net Gain

As one of the main focuses of the Government’s proposed Environmental Bill, ‘Biodiversity Net Gain’ is becoming a key topic of conversation in the development industry.

Prior to the UK’s departure from the European Union on 1st January 2020, the government’s Environmental Bill stated that:

However, post-Brexit, there is now a gap in environmental legislation, providing the opportunity to create a new Environmental Bill which includes ‘biodiversity net gain’, following a consultation period.

One of the aims of the consultation is to see if a standardised approach to biodiversity net gain is needed, and how this could be achieved. However, with the Bill currently under consideration by the House of Lords, it is yet to be finalised and could be subject to further amendments.

Is Biodiversity Net Gain a new concept?

The concept of leaving an environment in a better condition than it was before any development was done isn’t new. In fact, the National Planning Policy Framework already requires developments to deliver biodiversity net gains. However, to date, there has been no standard definition for this process, or a method to evaluate and measure net gain.

Historically, when ‘biodiversity net gain’ has been a project objective, a survey has taken place before any development work starts and is compared against the proposals. The proposed development would then take in to account the agreed mitigation, compensation and enhancement measures.

However, apart from an indication in proposals, there was no standardisation or specific way to measure if a biodiversity net gain would be achieved, making it difficult to compare separate developments and schemes.

Today, as a result of successful pilot schemes, the measurement of the net gain of biodiversity is done by a metric. Defra’s biodiversity metric, which is due to be updated in July 2021 after a consultation period, is set to supersede all other metrics and become the tool of choice across the industry.

However, when assessing a project with complex habitats for biodiversity net gain, caution must be exercised. This is because currently the metric only takes into account the habitat itself, not the wildlife and protected species that it supports. If a development enhances existing habitats, or creates new good quality habitats, it will in turn support wildlife and protected species – and this should be a consideration in the calculation of net gain.

Is Biodiversity Net Gain a useful measure?

Making biodiversity net gain part of UK law will deliver a clear, quantifiable way of securing environmental protection.

This is evidenced in the latest version of the Environmental Bill, which sets the compulsory net gain for most new developments at 10%, secured for at least 30 years. In addition, some areas deemed as ‘irreplaceable habitats’, such as ancient woodland, will be given special protection.

With government plans to increase housing and infrastructure across the UK, there could be significant increases in biodiversity.

Defra’s biodiversity metric will measure the land in terms of its:

  • Condition
  • Distinctiveness
  • Significance
  • Connection to other nearby habitats

Prior to the commencement of any work, the net gain score is calculated based on the above qualities, which are all rate on a scale and multiplied by the size of the site. This process is then carried out again at the end of the work to provide a second score.

To comply with government guidelines, there must be a 10% increase on the initial score, with important habitats and designated sites given priority.

If this model is standardised, anyone seeking planning permission will know what is required of any given site, and won’t have to watch out for the anomalies, which some planning authorities have picked up over time.

Using a single model across the UK will also help with ongoing biodiversity monitoring beyond new proposed developments. For example, it could help to identify areas in need of extra support, and make it easier to prove illegal activities, highlighting the impact they have had, and setting appropriate penalties.

What are the downsides to Biodiversity Net Gain?

Putting this into official legislation is a timely process. The Environment Bill has already faced many delays, and even when it gets Royal Assent, there is a further two-year transition period.

Defra’s standard model may also still need some fine-tuning, with additional areas added to their metric. From the importance of the land to people nearby, to the land’s contribution to the wider ecology, Defra has acknowledged that the metric has room to grow.

There are also some exemptions that the government has included alongside the Environmental Bill, despite Biodiversity Net Gain playing a central role in the legislation. For example, major infrastructure projects, and some urban brownfield sites, won’t have to adhere to the 10% biodiversity increase, and small developments with fewer than 10 residential units or covering less than half a hectare will be subject to a different metric. When you add this up across the country, this could account for huge chunks of land.

Concerns about a loophole that would allow some habitats to be completely destroyed, also post a threat. If biodiversity losses are unavoidable, biodiversity work can be delivered at another site through a ‘compensation’ scheme, or through ‘buying’ credits to fund work elsewhere.

As devolved governments handle all their own planning and environmental legislation, the Environmental Bill will only apply in England. Scotland, Wales and Northern Ireland could have their own set of regulations, which may or may not include the same level of biodiversity commitments.

What’s next for Biodiversity Net Gain?

It was hoped that the Environment Bill would be passed into law in Spring 2021, but we have yet to see this materialise.

However, despite these delays, some larger developers have already started to incorporate more protective and enhancing biodiversity measures to the habitats they are working on, in preparation for future legislative changes. Some local authorities are also stipulating that new developments must have a minimum of 10% biodiversity net gain.

There is also a clear movement towards looking after our country’s biodiversity, as evidenced by discussions around environmental protection at a legislative level. If this desire grows, and is backed up by a new Environmental Bill, biodiversity net gain will become a standard, yet vital part of responsible development.

To find out how your development can ensure Biodiversity Net Gain and protect vulnerable habitats, get in touch with us on 01225 459564 or email

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