Collington Winter Environmental

Biodiversity Net Gain Offsetting: Delivering BNG Off-Site

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What is biodiversity net gain?

The legislation surrounding biodiversity net gain (BNG) is already quite well-known across the UKs planning authorities. BNG is however, set to become mandatory within all development and planning applications towards the end of 2023.

BNG refers to the process in which a project or development site has to consider its impact on the surrounding habitats and environment. This means that developers must adapt their planning processes to ensure no damage is done to any local ecosystems.

A successful biodiversity net gain plan ultimately ensures that a developed area is to be left in a better condition for the environment than it was originally before project work began. This aim could be achieved through the enhancement of local habitats to protect local wildlife and ecosystems, both within and surrounding the development project.

Though it is not yet mandatory, local planning authorities have been requesting developers to meet BNG requirements for a while now in order to ensure everyone is already following the rules when the mandate comes in. BNG has and will essentially act as a planning condition and policy requirement for planning consent from local authorities. Therefore, you are much more likely to have your development approved if you show you are already complying with BNG requirements.

Biodiversity Net Gain Principles

The Chartered Institute of Ecology and Environmental Management (CIEEM) states that there are ten crucial good practice principles of biodiversity net gain. These should be met help to achieve BNG. The mandatory biodiversity net gain principles include the following:

  • Utilise the mitigation hierarchy to minimise the impact on biodiversity
  • Eliminate any negative impacts on biodiversity
  • Communicate each BNG outcome with complete transparency
  • Cover all areas of sustainability, including societal and economic factors
  • Involve any pre-development and post-development stakeholders in creating mandatory net gain solutions
  • Focus on producing long-term environmental benefits from BNG
  • Understand the variable factors and potential risks in order to achieve biodiversity and deliver net gain
  • Offer nature conservation that exceeds the stated BNG requirements
  • Determine a suitable method in order to secure measurable biodiversity net gains
  • Ensure the best possible results from biodiversity net gain


Calculating Biodiversity Net Gain

Every habitat gets scored on a biodiversity unit value in accordance to its important for biodiversity. This score enables an easy comparison between the existing value of a site and what the value will be once the site has been developed. The development may include enhancement of existing habitats or the creation of such off-site (biodiversity net gain offsetting).

Biodiversity net gain can be calculated through the DEFRA biodiversity metric 4.0, which requires a limited number of factors. These factors include:

 The type of habitat (both on and off site)

  • Any locations (if they are local environment priorities)
  • The size of habitat parcels in kilometres or hectares
  • The condition of any habitat parcels


You can also find a biodiversity metric 4.0 calculation tool on the government website which can help to determine your biodiversity unit score which can then be translated to your local planning authorities rules.

What is biodiversity net gain offsetting?

In some circumstances, the required 10% enhancement on biodiversity cannot be achieved on-site. Biodiversity net gain offsetting is essentially an act that ensures conservation measures are taken to off-site habitats and environments when biodiversity net gain is unable to take place on-site. This ultimately compensates for what is lost in a measurable way.

It is similar to how people have become more environmentally conscious of their carbon footprint. Some may choose to give to charities that plant trees after they have been on an airplane and want to give back to the environment to offset the carbon dioxide that was used on their trip.

There are pros and cons to biodiversity net gain offsetting. Some people feel strongly that the habitats and ecosystems that are being offset cannot be properly replaced or compensated elsewhere. However, biodiversity offsetting at least provides a chance of good by habitat enhancement elsewhere when a developer is going to develop a project regardless.

Offsetting, at least, ensures all developers either protect the environment they are using or do it somewhere else to ensure widespread biodiversity net gain in the long run.

Whether a developer is providing compensation on the site of their project or off the site, the scheme will use the Defra metric to calculate how many units they will need to pay for to successfully offset the loss due to their development project. Developers can then approach land management and offset providers who sell conservation projects that will deliver biodiversity and cover the number of units a developer has to legally cover and pay for.

Habitat banking has now been created to accommodate for the demand of delivering biodiversity net gain. Developers can use habitat banking to generate “conservation credits”. These credits can be purchased by a developer to ensure they comply with biodiversity net gain requirements.


When will biodiversity net gain be mandatory?

Following the Environment Act 2021, local planning authorities must require all permissions they grant to achieve at least 10% when measuring biodiversity. A provision for secondary legislation has been put into place from the act, which will set a date in which the mandate will come into force. The mandate is predicted to come into force in late 2023. The 2021 act gives a two-year transition period for authorities to get their policies and processes in place before it becomes mandatory.

The current national policy in England, The National Planning Policy Framework (NPPF) Paragraph 179 states:

“To protect and enhance biodiversity and geodiversity, plans should:

“Identify and pursue opportunities for securing measurable net gains for biodiversity.”

Paragraph 180 states:

“When determining planning applications, local planning authorities should apply the following principles: opportunities to improve biodiversity in and around developments should be integrated as part of their design, especially where this can secure measurable net gains for biodiversity”

Various Local Planning Authorities have been requesting the assessment for the past few years already. Many have introduced or are currently beginning to amend local developers’ processes to ensure they meet the required standard as part of Local Policy.

The Act will require the key points:

  • Developers must deliver BNG at a minimum of 10% through their schemes. This will be measured through a metric, currently Biodiversity Metric 4.0. This tool can help to identify your biodiversity unit score and translate it into the standards of local planning authorities.
  • A developer will need to demonstrate how biodiversity gain will be delivered on developed land. This will be demonstrated through the production of detailed Landscape Planting Schemes, Landscape Management Plans and Monitoring assessments for on and/or off-site.
  • A mitigation hierarchy is to be followed and demonstrated to avoid, minimise or compensate. If it is not possible to compensate on the development site, then offsetting will be required elsewhere.
  • Developers will have to guarantee the biodiversity gain is maintained for at least 30 years (as outlined in Landscape Management Plans).
  • New “local nature recovery strategies” will be prepared to geographically cover England by “responsible authorities”. This will encourage habitat creation and enhancement in the right places.
  • Conservation covenants will be a mechanism used to deliver this (this approach is in preparation by Defra and Natural England).
  • A national register of land used for biodiversity gain will be established. This will involve setting up a new biodiversity credits market.
  • Metrics are only concerned with habitats and do not take protected species into consideration.
  • Other ecological legislation and policies still apply. 

The aim is to get developers to think about mandatory biodiversity net gain during the initial land acquisition stage in order to avoid changing calculations once designs have already been produced. Having to redraft plans will typically lead to delays, unpredicted financial costs and difficulties with planning application determinations.

How can we assist?

Taking measures that prove you are trying to increase biodiversity net gain within your development project will further your chances to gain the required planning permission from your local authority when biodiversity net gain is mandatory. If this is not possible then biodiversity net gain offsetting is the route to take, and our experts can assist you with this process. Getting ahead of legislation and keeping up to date with current and upcoming laws surrounding the Environment Bills will ensure your development project runs as smoothly as possible.

 We can assist developers in attaining the required biodiversity net gain units through habitat banking and biodiversity net gain offsetting. We can also aid in securing them for 30 years to gain planning permission for their future developments.

Our team of ecologists are experts in the field of biodiversity net gain and can keep you up to date with new and changing legislation. As regulations can vary across local authorities it is important to instruct a qualified ecologist to ensure you are following the correct rules.

Our team’s experience and qualifications in BNG means we can support our clients pre and post development in order to reach the required mandatory biodiversity net gain bracket that is becoming law in autumn 2023. We are well versed with current and upcoming legislation including the Environment Bill, Town and Country Planning Act and Natural Environment and Rural Communities Act to name a few.

There are three stages of using the assessment, and we assist our clients during the very early stages of development, including promotions and land purchases. We are happy to complete an informal initial assessment for sites of interest. This helps our clients understand the probable implications and costings of Biodiversity Net Gain from the offset.

  • Project Feasibility

This involves identifying implication for potential development projects, audits of land for their BNG capacity and providing advice and options for BNG on and off site and the potential costs of offsetting.

Assessment and design

This stage includes baseline surveys and habitat condition assessments to provide data for the biodiversity metric and detailed design-phase input which aims to retain the best ecological features of the site with scope to create or enhance habitats.

  • Planning permission and delivery

This involves working with a project planning team to plan proportionate designs and management, as well as long-term management plans. This stage would also include liaising with local planning authorities if offsetting is required to agree on the delivery of biodiversity net gain.

To find out more how our team can help you with your biodiversity plans then please do not hesitate to get in touch with us to discuss your queries. Contact us using the details below.

Registered Office

23 Bark Street East, 1st Floor, Bolton



01204 939 608


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