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Biodiversity Net Gain case studies

Biodiversity net gain, or BNG, is a new obligation that will apply to almost all planning permissions and DCOs. Developers will be required to improve biodiversity by at least 10% compared with the situation before the development.

Read on for a selection of case studies which explore in detail the practical implications of Biodiversity Net Gain.

A commercial development in central London

How will regulation affect commercial developments in central London?

A commercial development in central London

The options for onsite BNG in an urban area will be more limited than in a rural one.  However some habitat types are suited to urban developments, namely green walls and green roofs. A ‘biodiverse green roof’ is of medium distinctiveness which means it is a more valuable habitat than most urban types.

London is made up of boroughs of relatively small areas and so one might think that the biodiversity unit discount for going outside the local authority area to find offsite BNG land would apply.  However, if land is in a different local authority area but in the same ‘National Character Area’ then there is no discount, and the whole of Greater London north of the River Thames is divided into only two National Character Areas, giving more flexibility in finding undiscounted offsite BNG land.

New housing on brownfield land in an already built-up area without much green space

How will regulation affect brownfield sites?

New housing on brownfield land in an already built-up area without much green space

How will regulation affect brownfield sites?

In this situation, the developer can either secure biodiversity units further away, but that may incur a penalty if the land is in a different local authority and national character area and mean more cost. Alternatively some onsite urban habitats that are recognised by the regime are worth considering: green walls, biodiverse green roofs and intensive green roofs.

An application for a temporary development for holiday homes.

If a development is temporary in duration, does the biodiversity net gain requirement still apply?

An application for a temporary development of five years

An application for a temporary development for holiday homes for a period of five years. If a development is temporary in duration, does the biodiversity net gain requirement still apply?

If a development is temporary in duration, then the BNG requirement will still apply.  It will be possible to rely on the original site value once it has been restored following the temporary use, but that would mean that it could not be built on again for at least 30 years and the additional 10% will still need to be found somewhere; further the length of the use will reduce the score according to the temporal multiplier.  It may be better to find offsite land if the development site is likely to be used again after the end of the temporary use.

A development of two fields with existing hedgerows.

What do I do when I have a development that features different biodiversity net gain metrics?

A development of two fields with existing hedgerows

A development of two fields with ditches and existing hedgerows which will feature a warehousing development. What do I do when I have a development that features different biodiversity net gain metrics?

Although much of the focus is on the main area metric, in this instance there are two other metrics involved in BNG, one for hedgerows and one for watercourses.  The rationale for this is that they are linear and don’t really have a meaningful area and so are treated differently.
In the case of the hedgerow it may well be the case that if it is being retained, the BNG requirement can be fulfilled simply by improving its condition, as many hedgerows are in a poor state.  If the hedgerow is to be lost, then another one elsewhere will have to be created or improved.  Note that you cannot ‘trade’ between the site, hedgerow and watercourse metric by having more in one and less in another – they must all meet the minimum 10% gain requirement.
In the case of watercourses even some very minor ones count towards the biodiversity score, eg a ditch that is full of water for at least four months of the year. As above you cannot ‘trade’ between the three metrics – and experience suggests that the watercourse metric is the most difficult to satisfy onsite. (It is also worth noting that lakes, which might be thought of as watercourses, are included in the main metric rather than the watercourse one). 

A housing development of no more than nine dwellings.

Does the obligation to provide biodiversity net gain for small developments differ?

A small housing development

A housing development of no more than nine dwellings. Does the obligation to provide biodiversity net gain for small developments differ?

The obligation to provide Biodiversity Net Gain is delayed until April 2024 for small developments such as this (the definition of small developments being nine or fewer dwellings or <0.5ha for a residential development where the number of dwellings is unknown at the time, or 1000sqm for non-residential development or <1ha if the floorspace is unknown at the time).  Such developments will also be able to take advantage of the ‘small sites’ metric, which is a bit simpler than the main metric calculation (but not much).

An application for change of use from an office to residential.

Does a change of use application require BNG provision even if there is no development?

A change of use application

An application for change of use from an office to residential

This may be a surprise to many, but a change of use application does require the provision of biodiversity net gain even if there is no physical development contemplated.  In most cases, the habitat score for the existing site will be zero as it will have been completely built upon and so no BNG is needed; however if it is non-zero, then something will have to be done. The existing habitat will provide for 100% of the biodiversity score but the extra 10% will need to be found through improvement onsite or by finding offsite biodiversity gain land.

An electrical substation for a large new windfarm off the coast.

How can preserving highly fertile land be balanced with the transition to net zero?

An electrical substation off the coast

An electrical substation for a large new windfarm off the coast of East Anglia. How can preserving highly fertile land be balanced with the transition to net zero?

Unfortunately the requirement for biodiversity net gain is unaffected by the nature of the development in question – however net zero aligned it might be, a minimum of 10% BNG will be required in all cases.  If it is the onshore element of a large new offshore windfarm and is all part of the same application however, this will require a DCO under the Planning Act 2008. On this point it is worth noting that the BNG obligation will not come into effect until November 2025, two years later than for planning applications.
Another point to note is that the fertility of the land, ie its ability to grow crops, is not relevant – it is its classification according to its (natural) habitat type that matters. 80 different habitats are listed and given a ‘distinctiveness’ score of 0, 2, 4, 6 or 8 in the biodiversity metric.

Several tower blocks to be built on brownfield land owned by TfL.

Decades of limited public access have allowed rare species to thrive. How should this be managed?

Several tower blocks on brownfield land

Several tower blocks are set to be built on land owned by TfL. It’s technically brownfield land, but decades of limited public access have led to several rare species finding a home there. How should this be managed?

This scenario reminds us that any animals living on land that is to be built upon do not affect the score under the biodiversity metric, it is only its description according to the plants living there that matters.  Of course if rare species are threatened then this would count heavily against the development outside of the requirement to provide biodiversity net gain, unless the effects were being overcome eg by safely translocating them elsewhere.

A development of several dozen homes in the south of England.

In an area where land is already expensive, might BNG credits make economic sense?

A residential development of a dozen homes

A development of several dozen homes in the south of England. In an area where land is already expensive, might BNG credits make economic sense?

There are two considerations to take into account here. Firstly, although more land would be needed if it is outside the local authority area in which the development is situated, land to provide biodiversity net gain does not need to be near the development in question. Therefore developers can use land in a cheaper area to offset the project.
Secondly as the government is keen to create a market in buying and selling biodiversity gain land, it has made ‘statutory credits’ (as it is calling them) deliberately expensive so as not to interfere with this market. In other words, it is unlikely that credits will make economic sense unless there really is no alternative.

A warehouse near the M1 in a deindustrialized area.

Is it possible for biodiversity units to be gained in an area with limited biodiversity?

A warehouse in a deindustrialised area

A warehouse near the M1 in a deindustrialized area of Yorkshire / East Midlands. Is it possible for biodiversity units to be gained in an area with limited biodiversity?

If an area currently has limited biodiversity then unless the land is significantly contaminated, it would make it easier to create sufficient onsite biodiversity to reach the 10% BNG threshold. It is likely that the existing score for the land according to the biodiversity metric will be low and therefore the required BNG land will be less than it would have been in an area of higher existing biodiversity.

What should I do about Biodiversity Net Gain?

Minimise the risks and seize the opportunities! Please get in touch if you have any specific questions.
We can advise on exploring Biodiversity Net Gain opportunities and keep you up-to-date with the fast-moving developments in this area.

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