Table of contents
Securing a 10% uplift can be tricky - each site is unique, and the needs are different. With the Biodiversity Net Gain Tool, you can easily assess different options. You should seek the best solution for your site - which doesn't just mean the maximum percentage uplift, but also wider considerations.
Reminder - AHBUs, HBUs and WBUs.
Under the BNG rules, you need to secure at least a 10% uplift in all three of the main categories of habitat if you have any of these habitats in your baseline.
Area Habitat Biodiversity Units (AHBUs)
Hedgerow Biodiversity Units (HBUs)
Watercourse Biodiversity Units (WBUs)
For example, if a site had grassland and a hedgerow but no watercourse, you would need to secure enough AHBUs to get a 10% uplift in AHBUs, and enough HBUs to get a 10% uplift in HBUs.
Questions you should ask about any proposed BNG solution
Even if you can secure the necessary percentage uplift on your site (usually 10%) you should ask yourself the following key questions before deciding to pursue this uplift:
Are your selections in keeping with the mitigation hierarchy?
Has the Local Planning Authority set out that there are any particular habitats they want to promote (e.g. as part of its Local Nature Recovery Strategy)?
Are your selections appropriate for the wider environment? While Joe's Blooms will always show uplifts permitted under the trading rules, you will also need to factor in how viable the transformation is for the site. You should give regard to:
the soil quality;
the habitat size and fragmentation;
any environmental limits to condition and distinctiveness;
any future use of the area which may degrade habitat type and condition;
Transitional habitat types;
whether or not the Lawton Principles apply; and
whether your proposed targets are ecologically viable within the project timeframe.
Does the habitat selected help conserve carbon or peatland creation?
Are there any specific rules that apply to the habitats that you are proposing to change/create? (A list of these rules is set out below). If so, have you fully complied with these rules?
Is the habitat in an area where an aerodrome operator may be concerned if the proposed uplift includes features likely to attract water fowl and other birds within safeguarding areas? (If this is true, the applicant is encouraged to engage with the Secretary of State for Defence (where this may affect a military aerodrome), the relevant aerodrome operator, and the local planning authority to understand the safeguarding considerations for their development before submitting the planning application).
The different ways to secure BNG uplifts
Under the Biodiversity Metric, there are different types of intervention you can take to secure the maximum number of Biodiversity Units (BUs). These are listed in the order that they should be considered).
Habitat retention. This is when you leave the habitat alone and leave it exactly the same as it was in the baseline assessment. This is the "avoidance" stage of the mitigation hierarchy, and where you reduce the negative impact of the development rather than create new BUs. Please note, you may need to provide evidence of how you plan to retain the condition of these habitats and, if you don't, you have to state that the habitat will be lost and that the same habitat will be created (in a lower condition) in 30+ years. (This approach was recommended in the Biodiversity Metric 4.0 User Guide but not the more recent statutory metric guide link)
Habitat enhancement. This is when there is either:
an improvement in condition compared to the baseline state
a change to a higher distinctiveness habitat within the same broad habitat group
Habitat creation. This is where one habitat type is replaced by another habitat and includes:
a loss of baseline habitat and its replacement with another
a change in broad habitat type (for example, a change from grassland to woodland).
Off-site BUs. This is when off-site units are purchased. Should only be considered if all of the above have failed to deliver the required BNG gains. You must make sure that any off-site BUs fully comply with the trading rules and have a completed off-site tab for your metric sheet.
Statutory credits. This is when statutory credits are purchased from DEFRA. Should only be pursued when there is a market failure, and there are no off-site BUs for sale. You must have a receipt of your purchase.
Note that on-site biodiversity gains should be secured for delivery within 12 months of the development being commenced or, where not possible, before occupation' (HM Government, February 2023, link).
Habitat Retention
AHBU Retention
This is where the baseline habitat is retained in its baseline condition, and there is no action to enhance or create the habitat. Please note that, according to older versions of the Biodiversity Metric, habitats subject to retention may still require ongoing intervention to maintain their baseline condition. If your LPA takes this view, you may need to document how these habitat conditions will be maintained for 30 years. You may wish to discuss with your LPA whether detailed plans are needed to show how the retained habitat(s) can be maintained over the period (30 years).
If the habitat can’t be maintained for 30 years, then the following should be added:
record the habitat as lost
record the same area and habitat type as created (in a lower condition)
set the ‘habitat created in advance’ function to 30+ years
provide an explanation in the assessor’s comments column
WBU Retention
Watercourse retention is where there are no interventions on the watercourse or riparian zone.
Habitat Enhancement
AHBU Enhancement
This is when there is:
an improvement in condition compared to the baseline state
a change to a higher distinctiveness habitat within the same broad habitat group compared to the baseline state
Condition must stay the same or improve, including when enhancing to a higher distinctiveness habitat.
When intertidal habitats are restored by re-establishing natural processes (for example, through managed realignments), the resulting habitat should be considered as ‘natural’ and not as an artificial habitat type (8.2.24 Biodiversity Metric 4.0, Natural England, Biodiversity Metric 4.0 User Guide, link)
Where ecologically viable, existing high or very high distinctiveness habitats may be recorded as an enhancement from the baseline, rather than creation. To be eligible there must be sufficient plant communities (of the target habitat) still visible in the degraded habitat at baseline (6.2.1 Biodiversity Metric 4.0, Natural England, Biodiversity Metric 4.0 User Guide, link)
WBU Enhancement
A watercourse is enhanced where the project interventions promote natural function, processes, and the development of natural habitats. Examples include:
removing culverts
restoring natural alignment
enhancing the riparian zone
removal of encroachment features
removal of tidal structures and restoration of tidal processes
Enhanced lengths may be longer than baseline lengths. For example, where meanders, channels or braiding are included.
Re-meandering may result in redundant former watercourse channels. If the watercourse is enhanced, you should:
not record any loss of watercourse length
record changes in area habitats separately
For example, if you create wet woodland in a redundant channel, record the creation of wet woodland within the area module.
Habitat Creation
AHBU Creation
Habitat creation is where one habitat type is replaced by another habitat and includes:
a loss of baseline habitat and its replacement with another
a change in broad habitat type (for example a change from grassland to woodland).
WBU Creation
If your watercourse interventions do not promote natural functions and processes, or the development of natural habitats, then this is creation. Examples include:
installing culverts
trapezoidal channels
channel straightening
physical modification
altering natural alignment
increases in encroachment
Record decreases in the baseline condition, length or distinctiveness of natural rivers as a loss of the impacted watercourse section.
Creation can also be the installation of a new length of canal or ditch where there is no applicable baseline loss.
You should record post-intervention lengths within the creation tab. Creation in advance may be set to 10+ if there are increases in encroachment with no other impacts.
The two parts to net gains
There are two parts to creating Biodiversity Net Gain:
Part 1: Restoring up to the baseline (ie. achieving no net loss). This is when you make up the harm that the development is doing (e.g. if you had a baseline of 10 units and you do 1 unit of damage, you need to get 2 units in order to get up to 11 units and meet the net gain target. The first unit (which brings you up to 10) would be the first part as, once you have secured that, you have achieved no net loss. (Another way to think about it is that, if your baseline biodiversity score was 100% and your development has brought this score down to 90%, this part is when you get the score back up to 100%.
Part 2: Securing Net Gains (i.e. past no net loss). This is when you have managed to secure your uplift and you are now trying to get to a 10% uplift*. These don't have to comply with the trading rules, though you should consider what habitats are appropriate for the site. (Another way to think about this is, if you have managed to get your score back up to 100%, this is the part where you get the score up to 110%).
*Please note that, if a LPA wants an uplift that is higher than 10% then you should read whatever your LPA's preferred percentage is here.
Rules you need to follow in the two parts
Part 1: Restoring up to the baseline (ie. achieving no net loss) | Part 2: Securing Net Gains (i.e. past no net loss) |
The habitats you select must comply with the trading rules.
The gains should be selected in compliance with the mitigation hierarchy (i.e. try to secure gains on-site before selecting off-site units) | The gains should be selected in compliance with the mitigation hierarchy (i.e. try to secure gains on-site before selecting off-site units). |
The Government has said that, if protected sites or species are on the site and are part of the mitigation, then at least 10% of the gain should be delivered through separate activities which are not required to mitigate or compensate for protected species impacts”. This means that at least 10% of the total (110+%) post-development biodiversity score should be from measures which are not undertaken to address impacts on protected species or protected sites (e.g. nutrient mitigation). For example, if a development has a baseline score of 10 biodiversity units and needs to achieve a score of 11 units, at least 1 unit should come from separate activities such as an onsite habitat or the wider market for biodiversity units (HM Government, February 2023, link).
Mosaics
Where a mosaic is not a defined mosaic it can be entered as separate habitat types. Assessors can map the component parts and estimate the proportion of each habitat component. For example, if a 10 ha habitat mosaic is estimated to be 75% calcareous grassland and 25% mixed scrub; this should be recorded as 7.5 ha of calcareous grassland and 2.5 ha of mixed scrub.
Intertidal habitats
When intertidal habitats are restored by re-establishing natural processes (for example, through managed realignments), the resulting habitat should be considered as ‘natural’ and not as an artificial habitat type (8.2.24 Natural England, Biodiversity Metric 4.0 User Guide, link).
Restored ‘natural’ intertidal habitats are identified in the metric as those that have been restored with the aim of biodiversity conservation either by reestablishing natural processes or with very limited engineering to support natural processes (2.3.9, Technical Annex 2, link).
Artificial habitats have been added to the metric where needed. The artificial intertidal sediment habitats are defined as being an ‘artificial’ example of the equivalent EUNIS habitat. The three artificial hard-substrate habitats
‘Artificial hard structures’
‘Features of artificial hard structures’
‘Artificial hard structures with integrated greening of grey infrastructure (IGGI)’
These are all man-made structures (2.3.10, Technical Annex 2, link).
Most natural intertidal habitats are of sufficient importance for nature conservation that they require a distinctiveness category of at least ‘high’. Most naturally occurring intertidal habitats are of high nature conservation value and are assigned a distinctiveness of ‘high’
Specific Habitat Rules
Ancient Woodland | Ancient woodland can be recorded as range of woodland habitat types and must be marked as an irreplaceable habitat within the biodiversity metric tool. Ancient woodlands include:
To ensure you record ASNW and PAWS, check:
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Intertidal habitats | Intertidal habitats are above water at low tide and under water at high tide and are defined in the metric according to the European Nature Information System (EUNIS) (2.3.1, Technical Annex 2, link). Assessors should identify EUNIS Level 4 and Level 5 to identify high value and irreplaceable habitats (2.3.8, Technical Annex 2, link).
The metric does not include subtidal habitats (which are habitats found below mean low water)(8.1.2, Natural England, Biodiversity Metric 4.0 User Guide, link). |
Cropland – arable field margins | This habitat parcel might contain areas which meet the definition of multiple habitat types. When assessing these habitat types, ensure that habitat types are mapped as individual habitat parcels to avoid under-recording biodiversity |
Grassland - floodplain wetland mosaic and CFGM | This is a ‘defined mosaic’ a habitat classification which include several habitat types as part of their primary definition. For baseline recording you should record these as their primary biodiversity metric habitat type. However, you should still record other habitats if these lie outside the primary habitat description. For example, a pond within this habitat should be recorded and assessed as a separate feature.
You should read the detailed rules in the official Biodiversity Metric User Guide |
Grassland – traditional orchard | This is a ‘defined mosaic’ a habitat classification which include several habitat types as part of their primary definition. For baseline recording you should record these as their primary biodiversity metric habitat type. However, you should still record other habitats if these lie outside the primary habitat description. For example, a pond within this habitat should be recorded and assessed as a separate feature. |
Individual Trees - Ancient and veteran Trees | All ancient and veteran trees must be recorded within the biodiversity metric tool and marked as an irreplaceable habitat. |
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Lakes – reservoirs | This habitat parcel might contain areas which meet the definition of multiple habitat types. When assessing these habitat types, ensure that habitat types are mapped as individual habitat parcels to avoid under-recording biodiversity |
Lakes - Temporary lakes ponds and pools | This is for Mediterranean temporary ponds (H3170) only. You should:
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Urban – allotments | This habitat parcel might contain areas which meet the definition of multiple habitat types. When assessing these habitat types, ensure that habitat types are mapped as individual habitat parcels to avoid under-recording biodiversity |
Urban – vegetated garden | This habitat parcel might contain areas which meet the definition of multiple habitat types. When assessing these habitat types, ensure that habitat types are mapped as individual habitat parcels to avoid under-recording biodiversity |
Urban – cemeteries and churchyards | This habitat parcel might contain areas which meet the definition of multiple habitat types. When assessing these habitat types, ensure that habitat types are mapped as individual habitat parcels to avoid under-recording biodiversity |
Urban - Greenwall | Where ground based green walls are planted, assessors should use the projected growth of the green wall over 30 years to calculate the vegetated area of the green wall |
Urban – sustainable drainage system | This habitat parcel might contain areas which meet the definition of multiple habitat types. When assessing these habitat types, ensure that habitat types are mapped as individual habitat parcels to avoid under-recording biodiversity |
Urban - open mosaic on previously developed land | This is a ‘defined mosaic’ a habitat classification which include several habitat types as part of their primary definition. For baseline recording, you should record these as their primary biodiversity metric habitat type. However, you should still record other habitats if these lie outside the primary habitat description. For example, a pond within this habitat should be recorded and assessed as a separate feature. |
Watercourses | Compensation for the loss of any watercourse units should be on a section of watercourse with similar habitat features (were it in a natural state). It should be of a similar size, function and stream order (rivers). For example:
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Ditch | Any ditches within recorded FWM-CFGM are part of the FWM-CFGM condition assessment and should not be recorded in separate modules
Some hedgerows and lines of trees have associated ditches. If these meet the definition of a watercourse ditch, you should:
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Woodland and forest - general | If a woodland is being created and it is not replacing the loss of a high distinctiveness woodland, you should input it into the biodiversity metric tool as either:
If woodland creation is required to compensate for the loss of high distinctiveness woodland, then:
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Woodland and forest - Felled | If woodland has been felled within your site and compensation is required for the loss, you must:
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Woodland and forest – wood-pasture and parkland | This is a ‘defined mosaic’, a habitat classification which includes several habitat types as part of their primary definition. You should record these as their primary biodiversity metric habitat type for baseline recording. However, you should still record other habitats if these lie outside the primary habitat description. For example, a pond within this habitat should be recorded and assessed as a separate feature. Do not use the habitat type ‘replacement for felled woodland’ to measure biodiversity net gain for other woodland operations, such as coppiced woodland or restocking. You must use the woodland type that was present prior to the coppicing or restocking as the baseline. |
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Hedgerow rules
Hedgerows are recorded as a centre line measurement along the length of the feature. Area habitats adjacent to hedgerows should be mapped to the centre line of the hedgerow. The footprint or canopy cover of a hedgerow or line of trees should not be subtracted from the total habitat area within a site. Likewise, the creation of hedgerows does not result in the loss of area habitat.
Hedgerows bounding green lanes, and double hedgerows should be recorded as two hedgerows rather than a single hedgerow.
Do not record overgrown non-native and ornamental hedges as lines of trees.
Where natural succession results in scrub growing directly adjacent to established hedgerows, meaning the hedgerow becomes less defined, you should:
• record the baseline hedgerow as retained
• show the hedgerow as retained in any post-development mapping
• record habitat changes (e.g. the establishment of scrub) adjacent to the hedgerow within the post-development sheet of the area habitat module