Achieving net gain for biodiversity - guidance for developers

At the earliest stage you should consider including as much land under your ownership or long-term control as necessary to deliver your 10% Biodiversity Net Gain On-site. This might not always be feasible but where adjacent or nearby land can be included in the Red Line this will make it more straight-forward to secure biodiversity enhancements mainly through planning conditions. The larger area of Red Line land will increase the overall Baseline value and therefore the 10% increase will also be higher, but if the additional land that is identified has a relatively low ecological value this should not be an issue.

Only land in the Red Line for planning application purposes can be classed as On-site. Any Blue Line land must be inputted in the metric as off-site and that land must be registered on the Natural England Site Register before the Pre-commencement Gain Plan condition is approved.

Registering land on the Natural England Site Register is a lengthy process involving approval of a 30-year management plan and a legal agreement to secure those biodiversity enhancements – and proof of that legal agreement appearing as a Local Land Charge.

It is unlikely that we will enter into a legal agreement (s106) as part of a live planning application to enable adjacent off-site land to be registered onto the Natural England Site Register. Such legal agreements are complex, costly and unlikely to be resolved before commencement of development so is best done well in advance of submitting a planning application.

There are numerous different ways that Biodiversity Net Gain can be achieved, one of these is to simply apply the Metric to an already designed layout and see what the numbers tell you. It is possible this approach will give you enough “numbers” to demonstrate you can achieve the minimum 10% net gain in biodiversity. However, Biodiversity Net Gain is more than just achieving biodiversity-by-numbers.       

The "Good Practice Principles for Development" provide an industry-standard having been produced from a range of the UK’s most respected professional bodies. They provide a way for industry to prove that development projects have followed best practice.        

These 10 Principles set out good practice for achieving Biodiversity Net Gain and must be applied together as one approach. It will be important to demonstrate against every Good Practice Principle that is has been considered and is being achieved. If only 9 out of 10 Principles are being achieved then Biodiversity Net Gain is not being achieved.        

The first objective should always be to seek to deliver 10% Biodiversity Net Gain On-site and therefore it will be essential to appoint a competent and experienced ecological consultant at the earliest stage to be involved in the initial design stage of the layout. The ecological consultant should work closely with the landscape architects and urban designers to consider which options of the layout lead to the best possible outcome for achieving Biodiversity Net Gain On-site.

This type of information should be included as part of the Design and Access Statement (if one is produced) or as a stand-alone assessment whereby different options of layout are shown with their corresponding different Biodiversity Unit outcomes. Where the layout resulting in the lowest impact on biodiversity has not been taken forward to the proposed layout stage an explanation should be provided why that option has not been chosen over another that is more damaging.

Evidence should be submitted as part of an Ecological Impact Assessment or Biodiversity Net Gain report to demonstrate the ecological consultant has been involved in the initial design stage of the layout in a meaningful way. 

This should include reference to the mitigation hierarchy of: 

• avoiding damage to sensitive ecological features
• minimising impacts on such sensitive ecological features

Where these first two steps of the mitigation hierarchy cannot be achieved (with an explanation to justify why not) consider and put forward an appropriate level of compensation that will be required either On-site or Off-site (or both).

The following information must be submitted to allow the LPA to validate the application:

Biodiversity Net Gain statement with written confirmation that:

• mandatory Biodiversity Net Gain does or does not apply
• whether any habitat degradation has taken place before or after the biodiversity metric calculations were carried out

The Statutory Biodiversity Metric with:

• baseline and Post-development calculations fully completed (Outline applications may provide indicative Post-development calculations)
• date of metric completion
• name of competent and/or Watercourse accredited person

A map showing:

• on-site habitat (using UK Habitat Classification) and any irreplaceable habitat

In addition to any other information on the Biodiversity and Planning web page,the following information should also be submitted at the outset to allow a timely consideration before Determination:

Accurate, scaled map/s showing:

• any habitats to be retained or enhanced – labelled to confirm a Biodiversity Construction Environmental Management Plan will apply to this area
• any areas where the council’s definition of Significant On-site Biodiversity Net Gain is proposed – labelled to confirm a Habitat Management and Monitoring Plan (HMMP) will apply to this area
• where Baseline and Post-development Biodiversity Units will occur On-site showing both UK HAB parcels and corresponding numbers of Biodiversity Units

Written justification:

• that all 10 Biodiversity Net Gain Good Practice Principles have been considered and can be achieved – this should be in a table format with a column for justifying the measures in place to achieve each Principle (not just a tick)
• demonstrating the habitat creation and/or enhancement measures are reasonably achievable
• explaining who will be responsible for funding the initial habitat creation/enhancement works, long-term management and habitat monitoring
• explaining who will be responsible for implementing the initial habitat creation/enhancement works, long-term management and habitat monitoring 

Condition Assessment sheets (unless the Small Sites Metric has been used) for each habitat parcel surveyed based on:

• botanical surveys at an appropriate time of year such as grassland surveys between May and September with sufficient quadrat survey data to demonstrate species diversity and abundance
• removal of cutting or grazing for at least 6 weeks prior to any botanical surveys for grasslands

Design and Access Statement (where produced) demonstrating:

• feasibility of different layout options to deliver 10% Biodiversity Net Gain On-site
• different Biodiversity Unit outcomes based on different layout options

If habitats are deemed to have been degraded before submission (or even after submission but prior to determination) then aerial photos (or other available evidence) will be used to decide the habitat type and an assumption of the highest scoring Condition category applied to calculate the Baseline value.

Land covered by a nature conservation designation or which meets the definition to be considered a Habitat of Principal Importance will be afforded protection under Local Plan Policy G8. The presumption should be for full retention of any land covered by a nature conservation designation or Habitat of Principal Importance, and any impacts (including indirect impacts) will need discussing early in the process with the LPA as bespoke compensation in addition to Biodiversity Net Gain may be required. Such discussions should normally take place under our Pre-application service.

Irreplaceable habitats are also afforded extra protection as per the NPPF, and where impacted will need urgent liaison with the LPA and bespoke compensation agreed if necessary.

Recreational impacts such as increased disturbance to wildlife on adjacent land or water quality impacts such as shading and pollutants from nearby road surfaces are examples of indirect impacts that may also need to be considered.

Where ecological surveys and/or advice from the LPA indicates that part of an application site may meet the West Yorkshire Local Wildlife Sites Criteria it will be expected that sufficient survey information will be gathered and the site will be assessed against the relevant Criteria as part of an Ecological Impact Assessment - and the presumption of retention in full where the Criteria are met. Any Biodiversity Net Gain measures included in the Metric to be delivered on land meeting the Local Wildlife Sites Criteria will need to be discussed with the LPA.

High - Nature Conservation Designations or Leeds Habitat Network

Medium - immediately adjacent to the above locations (such as physically connected)

Low - anywhere else in the district

However, once the West Yorkshire Local Nature Recovery Strategy has been formally approved the Baseline Strategic Significance score should always be Low. And the Post-development Strategic Significance score must only be scored as High for locations: Where there are Mapped Measures and the proposed biodiversity enhancements are fully in-line with a LNRS Measure for that Mapped location (the Measure must be stated and justified as achievable in the BNG assessment/report – and be agreed by the LPA).

Unless otherwise agreed with the LPA, Significant On-site Biodiversity Net Gain will apply to:

• 5 or more Biodiversity Units being delivered On-site (Habitats, Hedgerows and Watercourse Biodiversity Units added together)

And unless otherwise agreed with the LPA the total number of 5 Biodiversity Units will only apply to any habitats that are: 

• Equal to or more valuable than Low Distinctiveness in Good Condition

For example modified grassland (Low Distinctiveness) in Moderate Condition would not be included but Modified Grassland in Good Condition would be included.

The above definition of Significant On-site Biodiversity Net Gain has been chosen to quickly and easily identify the scenarios where this applies. Planning conditions and s106 obligations (as may be required) will then apply to those parts of the site. For clarity, this definition of Significant On-site Biodiversity Net Gain can consist of features being retained, created and/or enhanced.

In order to help identify and agree the parts of the site that will be referred to in planning conditions (see the next section of this guidance) two accurate scaled maps should be submitted before determination showing all biodiversity features that will:

1. Be retained (if applicable) through the construction phase
2. Deliver Significant On-Site Biodiversity Net Gain

A combination of planning conditions and s106 will be used to secure the implementation of Significant On-site BNG.

Planning conditions will be required for the following: 

• Biodiversity: Construction and Environmental Management Plan to protect features to be retained and/or enhanced
• Habitat Creation/Enhancement and Establishment Phase Strategy to agree the initial habitat creation and establishment works and how long this will take
• Significant On-site BNG Verification Report to demonstrate that any proposed new biodiversity features have been created/enhanced and have become established – before moving on to the 30-year management phase
• Habitat Management and Monitoring Plan (HMMP) for the 30-year management phase with confirmation of the start date for the HMMP 
• HMMP Progress Reports and an Updated HMMP in Year 5

The above planning conditions will help secure the initial habitat creation and establishment phase of Significant On-site BNG, together with the subsequent approval of the management plan and progress reports for the first 5 years of the management phase. These conditions have been designed sequentially so that information for each condition should only be submitted after the previous condition has been discharged.

A legal agreement (s106) will be required for the following medium and long-term delivery of Significant On-site BNG:

• Payment of the Council’s Significant On-site BNG Monitoring and Reporting Body sum
• Updated HMMPs in years 10, 20 and 30
• HMMP Progress Reports in years 10, 20 and 30

We expect any land delivering Significant On-site BNG to have interpretation panels which clearly explain the importance of the biodiversity features. The interpretation panels should explain that there is an active management plan and that habitat monitoring is taking place together with contact details where people can view copies of the management plan and progress reports. Such interpretation should help encourage a better connection to nature for those people living or working nearby, and lead to more successful implementation of the management plan through the local community understanding and supporting the need for the management that is carried out.

In Leeds, we are taking an active role in overseeing implementation of Significant On-site Biodiversity Net Gain. This will allow us to know whether Significant On-site Biodiversity Net Gain is being achieved from any consented planning permissions and report on these in our Biodiversity Duty, reporting to the Secretary of State under the Environment Act 2021.

This does not mean the LPA will be carrying out habitat monitoring, that is the responsibility of the developer or landowner. Instead, it means there will need to be submission and approval of:

• Initial Habitat Creation and Establishment Phase works
• Verification that the Establishment Phase works have been completed
• The 30-year management plan in the format of a Habitat Management and Monitoring Plan (HMMP)
• HMMP Progress Reports which include habitat monitoring in Years 1, 3, 5, 10, 20 and 30 which also demonstrate the annual work programmes are being implemented
• An updated HMMP in Years 5, 10, 20 and 30 with updated annual work programmes and revised management actions (if deemed necessary) arising from the HMMP Progress Reports

Where the management plan (HMMP) Progress Reports show that the previously approved numbers of Biodiversity Units are not being delivered to the satisfaction of the LPA there may need to be remedial measures agreed and included in an amended HMMP. Where progress is not satisfactory there may also need to be enforcement action. Site visits by the LPA to land delivering Significant On-site Biodiversity Net Gain will be required. To cover the long-term costs for our Monitoring and Reporting Body role there will be a charge made by the LPA.

In relation to Significant On-site Biodiversity Net Gain the charges are:

And £5 000 for each subsequent increase in 10 Biodiversity Units 

The above costs were approved on 10 September 2025 by our Chief Planning Officer (Decision Register) and will be reviewed annually to ensure they cover the full long-term costs associated with providing this role (and will be Index-linked). The charges are to cover both the initial establishment phase and longer-term management phase for Biodiversity Net Gain to be delivered. The LPA will use the s106 mechanism for this charge and unless otherwise agreed this payment will need to be made before commencement of development.

Where less than 5 Biodiversity Units are being delivered on-site there may need to be conditions for a Landscape Implementation Programme, Landscape Verification Report and Landscape Management Plan – but this will not normally require long-term habitat monitoring or progress reports to be sent to the LPA.

Watercourses cover a variety of features associated with slow-moving and fast-flowing water – and includes wet ditches (which contain water for at least 4 months per year), small streams, canals and covered culverts. If mandatory Biodiversity Net Gain is triggered due to adverse impacts on Habitats or Hedgerow Biodiversity Units and there is a watercourse which is less than 10 metres from the planning application boundary a River Condition Assessment (RCA) must be carried out by an RCA-accredited ecologist (unless for a covered culvert or within 5 metres of a wet ditch - in which case a Ditch Condition Assessment must be undertaken). The RCA-accredited ecologist must be named on the Start Page of the Biodiversity Metric together with submission of a copy of their certificate issued by Cartographer.

A copy of the fully completed RCA Condition and Encroachment Reporting Sheet will also need to be submitted.

Since the introduction of Biodiversity Net Gain there has been a lack of agreement concerning how Individual Trees should be scored in the Metric when there are other habitat types occupying the same physical space. 

In relation to other habitat types that can also be scored in the same areas of land there can be cases of double-counting such as if an area of grassland is proposed to be created or enhanced to become a meadow can this same parcel of land also have Individual Trees planted on it (sometimes referred to as an “over-sailing” habitat) and therefore have two different habitat scores applied to that same area of land through the Metric?

For clarity, we will not accept Individual Trees being scored on the same area of land that is also being proposed to deliver a meaningful quality biodiverse grassland. Any grassland that is underneath the ultimate canopy spread of a fully-grown tree (existing or newly planted) must only be scored as Modified Grassland in Poor Condition. If Individual Trees are being proposed in a grassland habitat then the ultimate canopy spread of those tree species when fully mature must be calculated (and shown on the UKHAB Classification map) in order to ensure Modified Grassland in Poor Condition is applied to that physical area.

Likewise with any grassland habitat being “over-sailed” by solar panels, the physical area underneath the solar panels must only be attributed to Modified Grassland in Poor Condition.

This approach reflects the impacts of either trees or solar panels through tree root interactions with the soil and/or shading which will lead to modifications of the grassland soil, fungi and plant community – hence treating such an “over-sailed” area with a modest low score in the Metric.

For clarity, where the intention is to create/enhance grassland to achieve Other Neutral Grassland (or other higher scoring grassland habitat) and also include Individual Trees or solar panels in the same area, the UKHAB Classification map for the Post-development scenario must show the grassland habitat being “over-sailed” by the eventual (at maturity) full canopy spread of any retained or newly planted trees (or extent of solar panels) and show this “over-sailed” area only as Modified Grassland in Poor Condition.

The mature canopy spread of many tree species can be found on the TDAG Tree Species Selection for Green Infrastructure or our own Guideline Distances from Development to Trees (the latter guidelines often show a smaller canopy spread due to being based on urban situations – so the largest of the canopy sizes in these two documents should normally be used).

Individual Trees must not be attributed scores in the Metric if the habitat being created or enhanced is Scrub (this would be double-counting because trees are already considered a natural component of Scrub).

However, Scrub habitat may be used for new tree planting as part of our 3:1 Tree Replacement Policy (LAND2) provided such trees are Heavy Standards at planting - but must not contribute towards Metric scores in addition to the Scrub habitat which they “over-sail”.

Within areas of existing Scrub, any trees/shrubs that are more than 5m tall and more than 7.5cm diameter at breast height (DBH) should be scored as Individual Trees in the Baseline Metric calculations.

There is another issue across the country that has caused disagreement in how it should be scored in the Metric due to different professional interpretations of available guidance and/or experience. It is whether an area of grassland should be classified as Modified Grassland (Low Distinctiveness) or Other Neutral Grassland (Medium Distinctiveness) – the former being lower scoring and is often identified in the Baseline value even when the latter should have been applied. Such cases lead to a lot of back-and-forth during determination when the LPA seeks more reassurance about the quality of the grassland present to avoid the Baseline value being under-scored. 

For clarity the UKHAB Classification definition of Modified Grassland g4 must be applied and referred to when justifying this category. This should only be applied to grasslands which are amenity grasslands such as those in formal parks and sports pitches, or most types of pasture under intensive agriculture – with broad-leaved species being restricted mainly to White Clover, Creeping Buttercup, Greater Plantain, Dandelion, Broad-leaved Dock and Chickweed. The UKHAB Field Key is also useful and indicates that only if the Rye-grass, White Clover and Timothy grass is more than 40% of the sward cover should it be classed as Modified Grassland. Other Neutral Grassland g3c must be applied if at least 3 of the following 4 criteria are met:

• >20% cover of broadleaved herbs and sedges
• >8 species per m² including forbs, grasses, sedges and rushes
• ≥1 grass species that is not generally sown for intensive agricultural production is at least abundant
• Cover of Rye-grass and White Clover is <30% 

Where Modified Grassland has been identified but there is any doubt whether it should be Other Neutral Grassland, there must be clear evidence submitted against how each of the 4 criteria (shown above) has been scored to demonstrate that Other Neutral Grassland has been considered and does not apply. This will assist the LPA to quickly agree with the type of grassland being scored. Evidence should consist of botanical surveys at a suitable time of year and only after a suitable period of no grazing or cutting i.e. between May and September after at least 6 weeks without grazing/cutting. There should be a suitable number of 1m² quadrat surveys using the DAFOR scale to demonstrate species diversity, with clear photographic evidence of the sward composition and quality.

In cases where there is disagreement about the quality of the grassland habitat present, we expect a FISC Level 4 surveyor to be appointed to apply the UKHAB Classification criteria for Other Neutral Grassland.

If there is still disagreement we may need NVC survey information. Any NVC communities which are MG1 (such as False Oat Grass) must be classed as Other Neutral Grassland, and only MG6 (unless g3c6) or MG7 is likely to be classed as Modified Grassland.

We do not want to see cases where Modified Grassland is being enhanced to Other Neutral Grassland, or Other Neutral Grassland is being created, without demonstrable evidence this can be delivered successfully. If this is being proposed we will need to see a commitment to soil testing and subsequent confirmation from a competent ecologist that the nutrient and phosphorus levels are suitable for the type of grassland being enhanced/created (planning conditions will need to include results of such soil testing and confirmation the soils are suitable).

Managing meadow areas is a specialist management operation so we will need confirmation of the organisation/contractor who will be carrying this out, and examples of their successful management of meadows from other sites. Details of the type of machinery that will carry out any meadow cutting will also be required. If there is no organisation/contractor in place for the site with a proven track-record of meadow management then only Modified Grassland should be proposed.

Where meadow areas are being proposed between rows of solar panels, or between numerous existing or proposed trees in a grassland area, in addition to the above evidence we also require confirmation from a competent ecologist that meadow management is practically realistic which should include confirmation of any specialist grass cutting and collecting machinery that can operate in constrained/small areas.

We want to encourage high quality Biodiversity Net Gain On-site and will scrutinise development not delivering this where it has not been sufficiently demonstrated why this is not feasible. However, it is acknowledged that there will be times where all of the 10% Biodiversity Net Gain cannot be delivered On-site.

It should be noted that by designing the On-site layout through input of a suitably competent and experienced ecologist there should be a smaller requirement for compensation Off-site. 

We also need to be satisfied that enough consideration has been made to retain any habitats of Medium (or higher) Distinctiveness (as per the BNG Mitigation Hierarchy).

Where some Off-site Biodiversity Units are required, we strongly encourage the use of habitat banks that are providing Biodiversity Units in the Leeds district. This will ensure that the compensation land is close to the development site impact leading to more opportunities for the people living and working in Leeds to have opportunities for contact with nature.

We want to see habitat bank land made available in the Leeds district.

There will be a cost to put in place a legal agreement that satisfies the Natural England Site Registration process but this is the best way for landowners with substantial areas of land (that can be dedicated long-term to nature) to start selling Biodiversity Units or use for their own subsequent development impacts arising from planning applications elsewhere.

We especially welcome landowners in Leeds who want to set up new habitat bank land in a way that creates new nature reserves or extends the size of existing nature reserves. Habitat banks that use large areas of land (with existing low ecological value) and create valuable new habitats with well-designed public access will leave a genuine legacy and be the best way to achieve win-win outcomes for both people and biodiversity – helping meet our Ambition to be a Nature Positive City and restoring our connections with nature.

We encourage landowners and other organisations looking to establish habitat banks in Leeds to look at the successful example of St. Aidan’s (near Swillington) whereby a new nature reserve was designed by the RSPB on a former development site. Today it is a 400 hectare wetland nature reserve with a nationally important bird population that will provide a long-lasting legacy.

We also want to see habitat bank land come forward which increases the size of existing high value ecological land such as immediately adjacent to Sites of Special Scientific Interest, Local Wildlife Sites and Ancient Woodland - ideally focussing on low ecological value land in these locations and enhancing it significantly. 

To find out more contact BNGS106@leeds.gov.uk and request a copy of our “Habitat Bank Criteria and Guidance” document and summary of costs that are likely to apply – in the subject of the e-mail state “New habitat bank land Enquiry”.

The council’s Executive Board on 7th February 2024 approved the setting up of a habitat bank so that Biodiversity Units can be sold to developers from enhancements taking place on Council land.  Once this habitat bank is set up developers will be able to consider using it as an option alongside other habitat banks operating in Leeds. To find out if a particular habitat type and number of Biodiversity Units are available contact BNG@leeds.gov.uk

All consented planning applications which mandatory Biodiversity Net Gain applies to will have a nationally imposed condition that will need to be formally discharged prior to commencement of development (as per wording in the Decision Notice). There is a national Biodiversity Gain Plan template that must be used and approved by the LPA – and it cannot be submitted until at least a day after notification of permission.

Provided you have followed the guidance on this webpage it should be straight-forward to fill in the Gain Plan and the LPA will already have considered much of the required information in order to allow a timely decision that the Gain Plan is satisfactory.

Note that the Gain Plan requires a Biodiversity Gain Site Register Reference Number for any Off-site land where Biodiversity Units have been purchased and allocated.

If Statutory Biodiversity Credits have been agreed as an acceptable Off-site solution by the LPA (instead of purchasing Biodiversity Units from a habitat bank) there will need to be proof of written consent for this approach from the LPA, and proof of purchase of any such Statutory Biodiversity Credits from Natural England.

As well as the Gain Plan template document the following items must also be submitted:

• the final Statutory Metric (fully completed)
• Condition Assessment Sheets for the On-site Baseline value (unless the Small Sites Metric has been used) Accurate scaled UK HAB maps for the Baseline and Post-development scenarios (unless the Small Sites Metric has been used)
• outline applications must provide details to demonstrate how the biodiversity gain objective will be achieved even if no detail is known about the layout

If you are also delivering Significant On-site Biodiversity Net Gain you must:

• refer to the relevant planning condition numbers and s106 details that have been applied in Question 4.8
• submit the information to also discharge the pre-commencement planning condition for the habitat creation and establishment phase
• ensure you have paid the Monitoring and Reporting sum that is specified in the s106 

If the Gain Plan is incomplete or further relevant information is required, the condition discharge application may be refused – in which case you will need to submit another condition discharge application.

Where a Custom or Self-Build exemption to providing Biodiversity Net Gain is engaged and agreed by the LPA, we will require a s106 agreement to be entered into which agrees the Baseline biodiversity value and delivery of 10% Biodiversity Net Gain specifically through Off-site purchase of Biodiversity Units should circumstances change post decision and the Custom or Self-Build exemption would thereafter no longer apply. This approach, which guards against Biodiversity Net Gain not being delivered in circumstances where it should, for example where the exemption would no longer apply post permission, has been supported by a planning inspector for a recent appeal case in Leeds, and will be kept under review in-line with any subsequent changes to Biodiversity Net Gain exemptions nationally.

Therefore, where such an exemption is engaged, applicants are encouraged to submit details of their legal representatives at the outset of a planning application in order to assist in timely decision making.

Retrospective planning applications are not exempt from Biodiversity Net Gain but the pre-commencement Biodiversity Gain Plan condition can not be used to demonstrate how the Biodiversity Net Gain has been delivered because development has already commenced (and has probably been completed). For clarity, where habitat degradation has been carried out as part of a Retrospective planning application we will still require Biodiversity Net Gain to be delivered. We will need to agree the pre-degradation Baseline value and use a planning condition or s106 agreement to ensure a scheme for Biodiversity Net Gain delivery is submitted within 6 months of the Decision Notice (if the application is consented).

Biodiversity Net Gain only relates to habitats so does not provide specific enhancements for species. Our Local Plan Policy G9 for biodiversity enhancements also applies to species, so enhancements for species need to be considered in addition to Biodiversity Net Gain. One example is the provision of integral bat roosting features and integral bird nesting features. In Leeds these should be provided at a building ratio of at least 1:2 (at least 50% of existing and/or new built structures should have either an integral bat roosting or integral Swift nesting feature).