BiodiversityCalculate metric:biodiversity calculateusing the biodiversity net gain of a project or developmentmetric

What the biodiversity metric is 

The biodiversity metric is a habitatformula basedused approachfor usedmeasuring tobiodiversity assessacross anall area’stypes valueof tohabitat, wildlife.including: 

• grassland 
• hedgerows 
• lakes  
• woodland 
• watercourses Thesuch metricas usesrivers habitatand featuresstreams 

For tothe calculatepurposes aof biodiversity value.net gain (BNG), biodiversity is measured in standardised biodiversity units. 

The biodiversity metric canmeasures bethe usedbiodiversity by:value of habitats by calculating the number of biodiversity units. The formula calculates: 

• ecologistshow ormany developersunits carryinga outhabitat acontains biodiversitybefore assessmentdevelopment takes place 
• developershow whomany haveunits commissionedare aneeded biodiversityto assessment
• planningreplace authoritiesthe whounits areof interpretinghabitat metriclost outputsand into aachieve planning10% applicationBNG, through the creation or enhancement of habitat  

The formula takes different factors into account, including the habitat’s: 

• communitiessize 
• quality 
• location 

For whocreated wantor toenhanced understandhabitats, the impactsformula also takes account of:  

• difficulty of acreation localor developmentenhancement 
• landownersthe ortime landit managerstakes whoa wanthabitat to providereach biodiversityits unitstarget condition 
• distance from theirthe siteshabitat to othersloss  

What

Except for small sites using the small sites metric, isa for

YouAn ecologist can useenter information into the biodiversity metric totool about the existing habitat and any planned development or enhancement. The tool will calculate the biodiversity value of the habitat, and how a development, or a change in land management, will change the biodiversity valuevalue.  For ofexample, athe site.tool Forcan example,measure the impact of building houses, planting a woodland or sowing a wildflower meadow.meadow.  

YouEarly canand repeated use of the biodiversity metric to:tool can help: 

• assess thea biodiversitysite unitto valuefind the number of biodiversity units an areaexisting ofhabitat landhas – its biodiversity value 
• demonstratecompare biodiversityBNG netproposals gainsfor a site - such as creating or lossesenhancing inhabitat, aon-site consistentor wayoff-site  
• measureplan habitat management decisions that promote biodiversity

Using the biodiversity metric tool  

Information to gather before using the tool  

For full details on how to find the information you need to use the tool and accounthow to use it, read the biodiversity metric tool user guide.  

You should also consult a professional ecologist, who will use the tool for directyour impactsproject, including gathering, inputting and assessing data. The Chartered Institute of Ecology and Environmental Management publishes guidance on how to find a suitable consultant. 

To use the biodiversity metric calculation tool, your ecologist will need to know:  

• the types of habitat, both present and planned  
• comparethe proposalssize of each ‘habitat parcel’ in hectares, or kilometres for alinear sitehabitats -(watercourse suchand ashedgerows)  
• the creatingcondition orof enhancingeach ‘habitat parcel’ 
• whether habitat on-siteparcels are in locations identified as local nature priorities in specific local plans or off-sitelocal nature recovery strategies 

ItA can‘habitat helpparcel’ youis design,a plansmaller area within a site, which contains one type of habitat. For example, a site may have a parcel of wet woodland habitat and makea landparcel managementof decisionspriority watercourse habitat. 

If you are making an on-site calculation, you will need to include everything that takeexists betterwithin accounta development’s red line boundary. This includes all features, whether or not they may be lost, retained or improved.

Which version of biodiversity.the metric tool to use 

A statutory (official) version of the biodiversity metric tool is available from 29 November 2023. We will provide a summary of what has changed from version 4.0 to the statutory (official) version. 

You shouldmust use the metricstatutory andversion calculatorof the tool withwhen ecologicalBNG advice.becomes mandatory. Do not use previous versions (4.0 or before) as these calculations will not be accepted in planning applications. 

The metric calculatestool has been used voluntarily in the valuesplanning assystem ‘biodiversityfor units’.several Biodiversityyears unitsand there have been several versions of it. All previous versions of the metric tool are calculatedpublished usingby Natural England.

If you already started calculations in version 4.0 or before, you will need to copy and paste these into the sizestatutory biodiversity metric tool. The outcomes of thecalculations habitat,for itsmost qualityhabitats will not change between metric version 4.0 and location.the statutory version. We will provide a summary of what has changed from version 4.0 to the statutory version.

Types

A detailed user guide for the statutory biodiversity metric is available. 

More information for developers 

As a developer, you can use the statutory biodiversity metric tool to assess: 

• the number of habitatbiodiversity units your proposed development has – its biodiversity value 
• how this value could be lost through development  
• what you need to do to achieve BNG 

You should enter details of your development site into the on-site part of the metric tool. If you haven’t achieved the 10% BNG, you will have to change the site design or consider off-site gains. You can use the tool to work out what off-site gains you would need on other land you own, or if you choose to buy off-site units from a landowner, you can: 

• choose an available gain site by exploring the marketplace 
• use that site for your calculations with the tool 

If you are not able to meet BNG requirements by making on-site or off-site gains, you can buy statutory biodiversity credits as a last resort, after submitting your biodiversity gain plan to your LPA demonstrating why statutory credits are the only option.  

There is guidance on statutory biodiversity credits, which explains how to use the statutory biodiversity metric fortool landto andcalculate intertidalhow habitats,many includingstatutory hedgerows,credits riversmay andbe streams.needed.

When to use the statutory biodiversity metric tool 

The biodiversity metric assessestool existingis habitatsnot intended to be a one-off step in your design and plannedplanning newprocess. habitatsIt’s createdadvisable byto ause developmentit repeatedly as you refine your plans. You should aim to get the best possible gains on site, before considering making off-site gains, or land(as change.a last resort) buying statutory credits. The tool will tell you where you could create more gains. Then you can make changes to your designs, and use the tool again to check your decision.  

Information

Within the tool, you needcan forsave your iterations as versions (for example 1.1, 1.2, 1.3). Submit the calculationfinal version to the LPA as part of your biodiversity gain plan. 

Start using the tool

ToFor example, the tool might calculate that developing on the woodland on your site would cost you 20 units, plus 2 to achieve net gain. But developing on modified grassland would only cost you 8 units, plus 0.8 to achieve net gain.  

Small sites: exceptions to having to use the statutory biodiversity metric calculationtool 

Small toolsites youare needonly required to know:achieve BNG from April 2024.  

Small developments are defined as not major developments under the Town and Country Planning (Development Management Procedure) (England) Order 2015. This means:  

• residential development where the typesnumber of habitatdwellings -is on-sitebetween 1 and off-site9, or if this is unknown, the site area is less than 0.5 hectares   
• thecommercial sizedevelopment ofwhere eachfloor habitatspace parcelcreated inis hectaresless -than 1,000 square metres or kilometrestotal ifsite itarea is linearless (riversthan and1 streams,hectare 
• development hedgerowsthat is not the winning and linesworking of trees)minerals or the use of land for mineral-working deposits 
• development that is not waste development 

If your project qualifies as a small site, you can use the conditionstatutory biodiversity metric tool, or if you prefer, you can use a simpler version of eachthe habitatbiodiversity parcelmetric tool, called the small sites metric (SSM).  

However, the SSM cannot be used on sites where: 

• whetherhabitats not available in the sitesSSM are inpresent 
• priority locationshabitats identifiedare aswithin localthe naturedevelopment prioritiessite (excluding some hedgerows and arable field margins) 
• European protected species are present on the development site 

Use

If you use the SSM, you do not have to do a condition assessment as part of your survey of existing habitat, as the values are fixed for all habitats assessed.  

If you use the SSM, you do not need an ecologist. You can use the simpler small sites biodiversity metric

The calculationsmall toolssites metric and a detailed user guide are available.

More information for land managers 

If you are a land manager, and considering selling habitat to gathera developer, you must use the informationmetric neededtool to prove you have accurately measured the biodiversity value of your habitat.  

When you have agreed to sell units to a development, fill in the off-site part of the statutory biodiversity metric tool for all habitat enhancements you are delivering for that development. Developers are responsible for submitting information about on-site gains, using the statutory biodiversity metric calculations.or the SSM.  

TheYou smallwill sitesneed to submit a completed metric andtool usercalculation guidewith your application to register your site for off-site gains. are 

More alsoinformation publishedfor onlocal Naturalplanning England’sauthorities Access(LPAs)

There tois Evidencefurther website.information for LPAs.

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