Biodiversity Net Gain (BNG) consultation puts nature at risk

Biodiversity Net Gain is a mandatory approach to planning development in England. It means developers must deliver a 10% gain in biodiversity as part of their plans. Developers must deliver a measurable improvement to nature by enhancing or creating new habitats including hedgerows or watercourses and ensure they're managed for at least 30 years.  

Developers must follow a series of steps that seek to avoid and minimise impacts to biodiversity.  

The first step is to avoid damage, and then look to enhance existing habitats on the site of their development. These can include things like green roofs, or street trees. They might need to undertake surveys or impact assessments, and then create a delivery plan.  

If developers can’t deliver all of their biodiversity gain onsite, they can look to deliver it off-site through dedicated habitat banks. This can be sites such as wildflower meadows and woodlands that are created and managed for 30 years through funding from BNG. 

Biodiversity Net Gain provides a way to measure nature improvements within the planning system. It means that developers can fund habitat creation and that landowners, including farmers, can be rewarded for restoring nature.   

Building developments can have a huge impact on wildlife and it’s only right that nature is not a victim. We support the principle that developers should make up for unavoidable loss by increasing natural habitats on-site or nearby. 

Done well, Biodiversity Net Gain can help development to protect these valued spaces in the first place, or to create and enhance places, for wildlife and for communities nearby.  

The proposal to change this fails to recognise the magnitude of the nature crisis – it will increase nature losses and cut wider public benefits in order to maximise profit for a few.  Additionally, the changes are unlikely to speed up development as it doesn’t address the root causes of delays.  

It isn’t all bad news. 

In the current system, some nature recovery projects - like the creation of ponds and wetlands - have to go through the same planning process. That means the also need to deliver Biodiversity Net Gain. This extra legal requirement can sometimes mean these projects become unviable, so no benefits to wildlife are delivered. 

We welcome this exemption, however, we cannot ignore the clear problems with other proposals.  

Consultations can be lengthy and complex to respond to, so we’ve tried to make it as easy as possible for everyone. 

Respond to the consultation

Defra needs to hear from the public about these changes - the following questions are key, and will form part of your response when you take action: 

Q5: Which of the following statements do you most support:  

1. No changes should be made to exemptions
2. Some changes should be made (please state which options you support with thresholds where applicable)
3. All minor development should be exempt

All you need to know about Question 5 and why it matters

BNG is currently a requirement for most developments, with a few exemptions. The consultation is seeking views on changes to the existing exemptions as well as the introduction of new exemptions.  

Through the changes, The Wildlife Trusts:  

• want to see improvements made to some of the exemptions which will rectify existing loopholes that are being used to avoid the BNG requirement
• support the introduction of a new exemption for development whose primary objective is to conserve or enhance biodiversity.
• do not want to see an increase in the number of housing and infrastructure developments being exempt from BNG, which some of the proposals will facilitate. 

We therefore support answer II – some changes should be made.  

Q8: Do you agree the area de minimis threshold should be extended? No 

All you need to know about Question 8 and why it matters

The ‘de-minimis’ exemption

Between September and December 2024 75% of non-householder planning applications claimed the de minimis exemption – therefore (as this consultation also states) it is not working as intended. 

The existing de-minimis exemption applies to developments that do not impact priority habitat and whose impact is less than 25 square meters of on-site habitat / 5 meters of onsite linear habitat. The de-minimis (minimal) size threshold applies to the sum of all habitat types within a development site, not the size of the development site as a whole. 

The intended purpose of this exemption (as set out in 2022 proposals for BNG) was to exempt development proposals, which result in negligible impacts or minimal impacts to low or medium distinctiveness. Examples of developments quoted in relation to the de-minimis exemption were: street furniture, and boundary walls.  

The consultation proposals: 

The  Government’s consultation is proposing an extension to the de-minimis size threshold (options offered are 50, 100, 250 square metres or Other). A large driver for this is because some minor developments that are impacting non-priority habitat just above the de-minimis threshold are finding it challenging to deliver the 10% requirement on site, and so have to go off site, but many developers claim this is prohibitively expensive for a small number/fraction of biodiversity units. 

The Wildlife Trusts’ view:

When first  proposed in 2022, The Wildlife Trusts did not support a de minimis threshold below which development would be exempt from the BNG requirement, particularly for habitats of medium distinctiveness or above. 

In Nature, size is not always directly linked to value. Small developments may have substantial indirect impacts on neighbouring sites, and cut through ecological corridors.  

Worse, small losses lead to cumulative loss, which can add-up considerably. 

While a small increase in the threshold for low distinctiveness habitats might be tolerated locally, the new proposal applies to habitats of both low and medium distinctiveness. 

If the new higher threshold of 250sq metres is brought forward, it would allow some minor and even some medium developments that meet the criteria to be delivered without BNG. As well as impacts on habitats, this could seriously impact new and establishing markets, by effectively making many developments exempt. 

We therefore do not support an extension to the de minimis requirement for medium distinctive habitats.  

Q11: Do you think the BNG requirement should be removed for minor development (for example including up to 9 residential homes)? No 

All you need to know about Q11 and why it matters

What is considered minor development? 

• Residential developments: between 1-9 dwellings on 1 hectare or less; or, if number of dwellings is unknown developments on an area of less than 0.5 hectares.
• Commercial development: where floor space created is less than 1000 square metres; or total site is less than 1 hectare.
• Development that is not the winning and working of minerals or use of land for mineral- working deposits
• Development that is not waste development. 

What do you need to know?  

• Minor development represents the majority of planning applications.
• There is already an existing exemption for householder applications
• There is already an existing de-minimis exemption (for developments that does not impact priority habitat and whose impact is less than 25 square meters of on-site habitat / 5 meters of onsite linear habitat) – which the consultation is looking to extend (see question 10)
• These exemptions do not cover all minor development that impact habitats, which in large numbers and taken collectively can have significant cumulative impacts on habitats and connectivity.
• The drivers behind the proposal are: increased costs and time (planning process); increased costs and viability to deliver small number of gains off site where on site not possible; and knowledge and expertise.  

The Wildlife Trusts view: 

This is one of the biggest concerns of the consultation. Making all minor developments exempt risks increased impacts to important habitats (BNG should work to deter building on important habitat) and reduce the habitat enhancement potential through BNG  

• Exempting minor sites will impact new and establishing markets – the consultation states 80% of transactions are for minor development BNG requirements. The new market is an important lever to drive private investment into nature.
• This will not fix the problem of faster build out – many other issues involved e.g skills shortage and supply shortage in construction industry.
• There are successful examples of minor developments achieving 10% BNG(as the consultation says), there are habitat delivery bodies making it easy for small developers to purchase fractions/small numbers of units (The Wildlife Trusts) + some LPAs setting up broker systems to pool small unit purchases.
• Mandatory BNG for minor sites was only introduced in April 2024 – it was never going to be perfect from day one, it needs time to embed and provide consistency and certainty for developers. We should be looking to fix the problems not throw it out at the first hurdle. This could be through making the small sites metric simpler. 

Q12: Please provide evidence for your response to the previous question - this is the comment box, recording your views on why it is important that all development gives back to nature.

Q13: If minor development were to be exempted from BNG, do you agree that the de minimis threshold should be extended to cover other types of development outside of the minor development category having little or no impact on biodiversity? No 

What you need to know about Q13 and why it matters

For all the reasons listed in response to question 8 and 11. 

The suggestion in the consultation is that if they bring forward a full exemption for minor development (as per question 11) they would not increase the de-minimis threshold (as per question 8) – ie it is currently posed as an either or package. 

However, the implication of this question is that they would consider doing both. Extending the de-minimis, could potentially be used for some medium sized developments that meet the criteria (those over 9 units). 

Q17: Do you agree that development whose sole or primary objective is to conserve or enhance biodiversity should be exempt from BNG? Please provide evidence where possible, including examples of developments that you think would be exempted. Yes 

What you need to know about Q17 and why it matters

Conservation projects that don’t fall within the de-minimis threshold are currently required to deliver a Biodiversity Net Gain. The 10% uplift in itself is rarely a problem, but legally securing and managing the land for 30 years which is a requirement of BNG has proved problematic for a number of schemes currently delivered on private land for example natural flood management schemes, peat restoration schemes, pond delivery for Great Crested Newt District Level Licensing. 

We are therefore supportive of this proposal, noting it will require clear guidance on what qualifies to ensure it is not exploited as a loophole by other development. 

Q20: Do you agree that temporary planning permission should be exempt from BNG? No 

What you need to know about Q20 and why it matters

The proposal is to exempt development which is considered to be temporary (temporary being up to 5 years), on the basis of the cost pressures, and additional burdens faced by the developer – as delivery can rarely be achieved on site.  

The Wildlife Trusts do not support this proposal: 

• Temporary permissions can still have significant and/or long-term impacts on biodiversity and should be properly compensated with a 10% gain.
• Although not intended to be permanent - five years is considered to be a very long time frame. Even for short periods – temporary developments can affect a range of wildlife both directly in terms of habitat loss and indirectly in terms of increased disturbance. With some leading to long-term and potentially irreversible damage to semi-natural habitats.
• Examples of temporary impacts can include: applications for caravans and other temporary accommodation on farms, temporary parking, vehicle movements and storage.
• If delivery isn’t possible within the wider development site then off site units should be purchased – there is a new and growing market to meet the need. 

Q25: Do you think the SSM should be able to be used on sites with European protected species present?  No 

What you need to know about Q25 and why it matters 

The Small Site Metric (SSM) was not designed to be used on sites where European Protected Species are present. We would not want to see a move to simplify the BNG assessment process for any site where European protected species are present. 

While, European protected species should be assessed and considered separately as part of a planning application and decision and while neither metric takes account of species – it is important to ensure a detailed assessment of the habitat that is supporting a particular European Protected Species. This is more likely to be achieved through the application of the full statutory metric. 

There is a risk that simplifying the approach to assessing BNG on a site important for a European protected species, could lead to further erosion of the assessment process. 

Q26: Do you think the Small Site Metric (SSM) should be able to be used on sites with protected sites present? No 

What you need to know about Q26 and why it matters

The Small Site Metric was not designed to be used on sites where protected sites or habitats are present.  

We would not support a move to simplify the approach used to assess the pre and post biodiversity value of a site. The statutory metric is weighted to steer development away from impacts to our most important sites and ensure where impacts do occur a greater levels of enhancement/creation are required. 

The full Defra consultation survey can be found here. 

Firstly, size doesn't always show how important an area is for wildlife. Even small building projects can cause big problems for nearby natural areas or break up the connections between different wildlife habitats.  

Small losses add up over time. When many small areas are damaged or destroyed, together they create an even bigger problem than each one alone. In short – small developments can have big environmental impacts, and exempting more projects from BNG requirements could cause serious harm to both wildlife and people.