What does Biodiversity Net Gain mean?

The phrase ‘Biodiversity Net Gain’ has been appearing a lot recently due to the government’s proposed Environment Bill.

After a consultation period, in Spring 2019 the government stated that Biodiversity Net Gain would be a compulsory element of the Environment Bill, being vital to secure planning consent in England. However, it’s still not completely clear what this will entail.

During the consultation, Biodiversity Net Gain was defined as:

“an approach which aims to leave the natural environment in a measurably better state than beforehand”

with the consultation focusing on whether there should be a standardised approach for this, how it could be implemented and how it should be measured.

While the consultation has now ended, the Environment Bill is still in the process of being passed into law, so there’s still some uncertainty about the final form it will take.

What is Biodiversity Net Gain?

Biodiversity Net Gain has been used for a long time to describe leaving a habitat in a better state than it was before human intervention. This includes development and land management.

In order to assess this, a survey of the habitat is carried out before any work is completed. The results of the survey are turned into ‘biodiversity units’ which can then be compared to a second survey carried out once the development work has been completed. However, there are many different ways to calculate these ‘units’ – Defra has it’s own biodiversity metric which is used a lot in the UK, but many organisations and local authorities have their own metrics, so the results aren’t always directly comparable.

It’s also down to individual planning authorities to decide how to assess and enforce these measures.

Depending on how the units are defined, they can be a bit of a blunt tool to tackle a complex issue – for example, species unique to a particular area could be significantly negatively impacted, but if a more common species thrives, the overall net gain could be deemed positive.

What are the benefits of enforcing Biodiversity Net Gain?

The obvious benefit of Biodiversity Net Gain is the higher level of environmental protection which will be embedded in law. Most new developments will have a mandatory net gain of 10% for at least 30 years, and with plans for increased housing and infrastructure, this could have huge benefits for our habitats.

The government statement outlines more details about special protections for ‘irreplaceable habitats’ which should avoid putting unique UK species at risk.

The statement uses Defra’s definition of net gain and their biodiversity metric, which takes into account distinctiveness, condition, strategic significance and habitat connectivity. This means things like Defra’s habitat classifications, the type and condition of the land, how it compares locally and nationally, and how the habitat interacts with those around it should all be evaluated and scored.

These scores are multiplied by the size of the site to give the overall baseline score, which should be consistent with assessments made in other parts of the country. Scores won’t override any existing protections put in place to protect particular species or habitats, and designated sites will also remain protected.

A standardised model of calculating biodiversity should make it easier for planners and those seeking planning consent to understand exactly what measures will be required at any given site, removing a lot of the red tape and irregularities between different planning authorities.

Part of the monitoring of biodiversity will include mapping current levels and identifying areas which could be enhanced – so, as well as ear-marking areas which could benefit from a net gain, there will be a record of biodiversity in any area which is illegally developed, making it easier to understand the impact that development has had and setting penalties accordingly.

What about the negatives?

It’s going to take a while for this to come into effect, with a two-year transition period once the Environment Bill gets passed into law – and there is currently no indication as to how long that will take.

Once the law is passed, Defra acknowledges itself that there are other areas that need to be taken into consideration in order to get a full picture of a particular habitat, such as its structure, its ecological functionality and how the site is used or appreciated by people.

As well as this, the government have already created some exemptions, such as:

  • Major infrastructure projects and marine sites
  • Certain urban brownfield sites
  • Smaller developments with less than 10 residential units or an area below 0.5 hectares
  • Building extensions

This means, particularly with infrastructure projects, huge areas of land could be developed with no necessity to protect or promote natural habitats.

There is also now an option for ‘compensation’ at a site away from the development, or to buy biodiversity credits if it’s deemed that biodiversity losses can’t be avoided. This means it’s possible that none of a habitat in a particular area is conserved, and the biodiversity requirements are fulfilled on a separate site – leaving some areas in a worse situation than they would be under current planning regulations.

Again, some types of habitat will be exempt from this, such as ancient woodlands and sand dunes, but potentially large areas which are currently protected will be at risk of development.

Finally, as with other planning and environmental legislation, this only applies in England, so architects, developers and others working across the UK may have to get used to varying levels of compliance and red tape depending on which country the work falls within.

Looking Ahead

With the Environment Bill still on indefinite hold while it goes between the House of Commons and the House of Lords, it’s impossible to know when Biodiversity Net Gain will become a compulsory part of planning legislation in England.

In the meantime, some larger developers have already started to include increased levels of habitat protection and enhancement in preparation, and we know that areas of special interest will continue to be protected.

While there seem to be some loopholes regarding infrastructure and using off-site biodiversity ‘compensation,’ overall the picture looks positive in terms of protecting and enhancing biodiversity across England.

If you’d like more information about Biodiversity Net Gain and how to incorporate it into your plans, get in touch with us on 01225 459564 or email

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