Baker Consultants

Biodiversity net gain Metric 3.0 & How it will impact your land development plans?

The Biodiversity Net Gain Metric Version 3.0 was finalised in July earlier this year, introducing a new standard whereby developers, land owners, local planning authorities and ecology consultants can measure the impact of new development on biodiversity.

The use of this tool ensures that developments meet the Environment Bill’s latest requirement for a 10% biodiversity net gain on development sites. So, what does the implementation of metric version 3.0 mean for land owners and developers, and how does it differ from the previous 2.0 version?


Condition Assessment

Condition assessments for various habitats have changed slightly within the new metric, providing clear and robust criteria that incorporates a more consistent recording process in the field. Each broad habitat type has its own condition assessment sheet, where a set number of criteria must be met to achieve a certain condition. Some of these criteria are specific to a species, requiring the surveyor to correctly identify positive and negative indicator species.

Evidence of each habitat area’s condition assessment must also be provided to qualify the decisions made within the metric. This means ecological surveyors need to be suitably qualified in the botanical identification skills that are required to assess specific habitat types that are likely to be present on various sites. This also makes appropriately timed surveys critical, as some conditions may not be immediately obvious or assessable outside of summer months. Andrew Baker, Baker Consultants’ Managing Director, recently gave expert evidence to a public inquiry where he discovered that an ecological survey had misidentified a grassland habitat, tripling the BNG value and putting the entire project in jeopardy. Getting the BNG calculation wrong has real world consequences – it not simply an accountancy exercise.


Biodiversity Net Gain Metric 3.0 vs. Biodiversity Net Gain Metric 2.0

Various functionalities of the previous metric have been removed due to concerns over their usage, such as habitat connectivity. This measurement was often neglected or used incorrectly due to mixed interpretation of the guidance and left little room for professional judgement.

In place of features that have been removed from the 2.0 metric, new features have been added to Version 3.0. The ‘Advanced/Delayed Creation/Enhancement of Habitats’ recognises that in some instances, such as phased development proposals, habitats may be created in advance of development or after development has taken place. This means that if a habitat is enhanced or created in advance of development works or after they have been carried out, the site will be given a heavier weighting in Biodiversity Units; this means it is not worth getting BNG in place in advance and banking the units.

Other changes have been introduced within the new metric to better reflect the biodiversity value provided by some habitats. Previously, for example, if assessed as being in good condition, bramble scrub (by unit area) offered one of the best Biodiversity Unit values due to its ease of creation. In Biodiversity Metric 3.0, this habitat is fixed at poor condition, greatly reducing its value within the calculator and incentivising the creation of more valuable/complex habitats, such as mixed scrub and grasslands.

One of the more prominent changes to the Biodiversity Net Gain Metric is the removal of habitat type ‘Suburban/Mosaic of Developed/Natural Surface’, which will impact developers who are submitting early outline plans and want to assess the feasibility of Biodiversity Net Gain before a detailed design phase commences. This habitat type was considered to be of low distinctiveness and was frequently used to measure proposed urban areas of residential developments, where specific areas of housing, infrastructure and gardens/amenity greenspace had yet to be defined. In version 3.0 of the metric, this is now replaced by guidance stating that a combination of ‘developed land, sealed surface’ and ‘vegetated gardens’, both of very low distinctiveness, is used at a 70:30 split of the total urban development area. This results in approximately 70% less Biodiversity Units for this type of measurement.


It’s also important to note that schemes which have already used Version 2.0 to assess biodiversity net gain can continue to do so unless the baseline habitat data has changed or there is likely to be a substantial difference between the results from each metric version.

Biodiversity Net Gain Metric streamlines much of the development planning process and ensures that loses are compensated. The system steers developers away from sites that have a high biodiversity value as there are direct financial consequences for building on such sites. Currently, however, before the Environment Bill gains royal assent the legal mechanisms for delivery BNG units are not established. We are therefore currently trapped in a no man’s land between the Environment Bill on one hand and on the other the policy requirements of the NPPF and local plans that seek to secure net gain for biodiversity.


If you need advice related to ecology, surveys or conservation, then please get in touch with us via our contact form on the website, or you can call us on +44 (0)1629 593958 or email us on