Biodiversity net gain

Biodiversity is the variety of animals, plants and other living things. Biodiversity net gain (BNG) is a development approach that seeks to enhance the biodiversity of a site over a fixed period of time, ultimately resulting in a higher biodiversity value than prior to the development.

The biodiversity value of a site is measured prior to development to establish the baseline. This involves an assessment of the types of habitat present such as grassland, woodland, heathland or hedgerow, and a condition assessment to establish the quality of the habitats present. A second biodiversity assessment of the post-development site design and landscaping proposals is then carried out to establish the biodiversity unit value of the completed development, using the same criteria as the baseline assessment. The aim of BNG is for the post-development biodiversity value to be higher than the baseline. BNG aims to halt the national net loss of biodiversity, to reverse the decline and to support the delivery of higher quality, better connected ecological networks.

The minimum legal increase required by BNG is 10%, however more is encouraged. This will need to be maintained for 30 years post completion.

The following are the most common planning applications within the borough that are legally exempt from BNG:

• householder applications
• non-foundational applications (e.g. reserved matters where outline was before BNG applied)
• small self-build/custom residential developments (see below)
• those which fall under the minimum impact threshold (see below)
• those purely for BNG works
• section 73 applications (variation or removal of condition) unless there would be a change in biodiversity value (see below).

The minimum impact threshold (de minimis) applies where both:

• no priority habitat is harmed, and
• any habitat harmed (which scores more than 0 on the metric) totals less than 25m2 of area habitat or 5m of hedgerows or watercourses.

The small self-build and custom build exemption stands if all of the following apply:

• if there are less than 10 dwellings
• the total site is less than 0.5ha, and
• it is entirely self-build or custom residential development.

Section 73 permissions are generally exempt. However, if any conditions attached to the new planning permission, granted under section 73, do affect the post-development biodiversity value, then a Biodiversity Gain Plan for the new permission must be submitted and approved prior to the commencement of the permission.

Visit the GOV.UK website to read the BNG Planning Practice Guidance for more information on exemptions

Developments will need to measure the amount of biodiversity present before development, through a formal assessment of the habitats present. Some habitats are less common or contain more species than others. Therefore, all habitats are graded into bands of “Habitat Distinctiveness”. Those in higher bands and in better condition will get more “Biodiversity Units” than others. Biodiversity Units are effectively the unit of value for BNG.

The Units are automatically calculated in one of two standard spreadsheets (the Statutory Metric or the Statutory Small Sites’ Metric). There are a number of rules and principles to follow, however the Metrics help guide you through some of these.

The following diagram aims to explain habitat distinctiveness and the some of the rules around the biodiversity gain hierarchy (which will be explained further below). It also shows how some, but not all, habitats can be exchanged with those of the same or higher distinctiveness, through development. However, one basic rule is that there are three types of units; Area, Hedgerow and Watercourse. These are completely separate and cannot be interchanged.

We are legally required to check you have complied with these rules throughout the BNG process.

The standard planning application form will ask you several questions regarding BNG including if you think it is exempt, why. If BNG is required, you will need to submit your metric along with a habitat map. These will be needed to validate your application and be used to help determine planning permission.

If your habitat on site has been intentionally damaged since 30th January 2020, in a way which reduces its biodiversity units, through activities not covered by any planning permission, you must discuss this with us. You will need to agree with us your baseline date for your Metric, which must reflect the conditions on site before this happened. Checking aerial photographs of your site from 2019 onwards is one of steps we must take in deciding your application.

Following planning permission, you will be required to submit further details about how you are going to deliver a minimum of 10% BNG and maintain it for 30 years post-completion. This will be in the form of standard documents including a Biodiversity Gain Plan. This will need to be discharged before you commencement development.

In these document/s you will need to set out how you are going to monitor the condition of your biodiversity over the 30 years post-completion and the dates that your monitoring reports will be submitted to the LPA for assessment. See below for more information on this, however, we are expecting them to be submitted in years 1, 2, 3, 5, 7, 10, 15, 20, 25 and 30 following completion of your habitat enhancement and/or creation.

Wherever possible the biodiversity should be protected and enhanced on the application site. There may be circumstances which mean you need to deliver this offsite, however legally we must check to make sure you have followed the Biodiversity Gain Hierarchy which is set out below in order of priority:

For habitats of medium distinctiveness or higher it requires:

If this is not possible, and the loss is considered acceptable in planning terms, the remainder of the hierarchy applies to compensate for their loss. The following must also be followed for all habitats with a distinctiveness below medium:

1. the avoidance of adverse effects from the development
2. if they cannot be avoided, the mitigation of those effects

If this is not possible, and the loss is considered acceptable in planning terms, the remainder of the hierarchy applies to compensate for their loss. The following must also be followed for all habitats with a distinctiveness below medium:

3. enhancement of existing onsite habitats
4. creation of new onsite habitats
5. allocation of registered offsite gains
6. purchase of biodiversity credits.

Offsite delivery of BNG is usually undertaken by third party landowners and the sale of units is officially registered. As the market is new, there is currently very little supply of units available, however it is hoped that this will increase in time. Telford & Wrekin Council are looking to provide some units, however the council is an equal partner within the wider market and the units on offer are limited. Please note: that all evidence to date shows that delivering offsite biodiversity units is much more expensive than delivering them onsite.

If no units are available from the market, the Government has a system of Conservation Credits that can be acquired as a matter of last resort. The cost of Conservation Credits has been deliberately set at a much higher rate than the market’s Biodiversity Units.

Legally the applicant only has to provide much of the detail after planning permission has been given. However, not considering this information from the start of your design process risks you getting a planning permission that you cannot afford to build out. Therefore, we strongly encourage you to incorporate BNG within your layout design process from the start, to evaluate your development’s viability. Simple cost effective changes in layout and design can make a huge difference in both the loss and gain of onsite biodiversity units. This will be reflected in your overall development costs.

As BNG is a statutory requirement, we are legally unable to grant consent for developments to begin where they deliver less than 10% net gain, even if your project’s viability is affected by it.

Wherever possible, we have complied closely with national guidance to provide some level of consistency in this new process. However, there are some areas where local definition is required, or national guidance is open to interpretation. The following aims to clarify our position on these issues.

Areas of High Strategic Significance are wildlife-rich areas and corridors. They are used within the Metric calculation to raise the score of habitats within these locations to reflect their relative importance. They will be defined in the Shropshire and Telford & Wrekin Local Nature Recovery Strategy (LNRS). These strategies are being actively compiled across England and will be published in due course. As the LNRS progresses we will incorporate its draft findings.

Until our LNRS is adopted, we are following the national guidance to define these areas locally. We consider these to be:

More information on how we have selected Areas of High Strategic Significance:

The criteria and guidance we have based our selection on is set out on page 26 of Defra’s The Statutory Biodiversity Metric User Guide (Feb 2024) 

View the DEFRA Statutory Metric User Guide here

The documents considered relevant within the borough are:

• Telford and Wrekin Local Plan 2011-2031 (including Neighbourhood Plans)
• Shropshire Biodiversity Action Plans
• River Basin Management Plan including Catchment Plans and Catchment Planning Systems

Each of these documents were produced for different purposes and it is likely some interpretation will be required in the definition process. We aim to refine this over time. However, in the interim, the following will be used to define an area of High Strategic Significance:

Areas designated within Telford & Wrekin Local Plan as any of the following:

• Site of Special Scientific Interest
• Local Nature Reserve (including proposed)
• Local Wildlife Site
• Local Geological Site
• Green Network
• Area of Outstanding Natural Beauty (now National Landscape)
• Ancient Woodland

View these sites on our online interactive map

Local Green Spaces are designated in the following Neighbourhood Plans and are also considered to be of High Strategic Significance:

Edgmond Neighbourhood Plan

Lilleshall Neighbourhood Plan 

Madeley Neighbourhood Plan (Policies Map)

Newport Neighbourhood Plan

The Shropshire Biodiversity Action Plan text states that the local definitions are now out of date and we should defer to the national list of Habitats of Principal Importance. These are known as Priority Habitats.

View the Shropshire Biodiversity Action Plan

There is currently no detailed mapping yet for these habitats locally, however your surveys will assess for them. The following links are national mapping tools which will be used to assess their presence:

Visit DEFRA Magic Maps

Visit the Woodland Trust Tree Search

Using the River Basin Management Plan we will consider areas shown on this map within the Ecological Objectives: Lakes and Ecological Objectives: Rivers, Canals, SWTs layers as being of Strategic Importance. 

View the local River Basin Management Plans

View information about the Severn Middle Shropshire Catchment

View information about the Severn Middle Worcestershire Catchment

Significant onsite habitat enhancements require securing via condition or legal agreement. The definition given in guidance is being actively explored across the professions. However, until there is a more precise definition we will apply the guidance of what does, and does not, constitute significant on-site enhancements.

View government guidance about significant on-site enhancements

Monitoring Report periodicity: Until further guidance is available, we will require monitoring plans to be submitted to us in years 1, 2, 3, 5, 7, 10, 15, 20, 25 and 30 following completion of the habitat enhancement and/or creation. This schedule should be presented in your Habitat Management and Monitoring Plan which will be submitted at condition stage. However, in some ecological circumstances there may need to be a revised timetable, to reflect BNG works on a particular habitat or site. These will need to be agreed with ourselves in advance.

This schedule provides more observation at the start when most of the key establishment is occurring and intervention is most likely to steer your management. Different habitats mature at different rates, however we have chosen this blanket approach for pragmatism, to simplify your monitoring returns.

• View government BNG guidance collection.
• View BNG Planning Practice Guidance.
• View BNG guidance for developers.
• Visit the DEFRA Statutory Metrics webpage.
• Visit the Biodiversity Gain Plan webpage.
• Visit the Habitat Management and Monitoring Plan and Monitorin Report template.