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Biodiversity Net Gain Offsetting: Delivering BNG for Developments

What is biodiversity net gain?

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

Biodiversity net gain is a concept in conservation biology that aims to ensure that new development projects result in an overall increase in biodiversity rather than just avoiding or mitigating negative impacts on biodiversity.

This can be achieved through a variety of measures, such as creating new habitats, restoring degraded habitats, and protecting and managing existing habitats. The ultimate goal of biodiversity net gain is to enhance the resilience and functioning of ecosystems while also providing benefits to people and reducing biodiversity net loss.

when will biodiversity net gain be mandatory

What is the Environmental Act 2021?

The Environment Bill was passed in 2021 after recommendations from Natural England, and BNG will soon become legally binding through the forthcoming Environment Act in 2023.

George Eustice, the Environment Secretary, has praised the Act as being the “most ambitious environmental programme of any country on earth”. The focus of the act is to put the environment at the heart of the economy, promoting sustainability, traceability, and biodiversity protection. The Act became law during COP26 in Glasgow.

The Environment Act 2021 has led to the creation of the ‘Office for Environmental Protection’ (OEP). This independent office is responsible for holding the government and public body organisations to account for the obligations set out by the Act and future legislation. 

Some of the headline measures include protecting rainforests and reducing the impact of sewage discharges from storm overflows. The Environment Act 2021 aims to halt the decline in species by the end of the decade by preventing deforestation and requiring new developments to create and improve surrounding habitats. The act’s purpose is to address the issues of climate change and the loss of biodiversity by taking protective and proactive steps.

At Collington Winter, 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.

What are the principles of biodiversity?

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 to help 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

Each habitat is scored on a biodiversity net gain unit value in accordance with its relevance to biodiversity. This score enables a comparison between the existing value of a site and what the value will be following the site’s development. The development may include the enhancement of existing habitats or the creation of such off-site.

Biodiversity net gain can be calculated through the DEFRA biodiversity metric 3.1, 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 3.1 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’ regulations.

Biodiversity net gain assessment

There are three stages of a biodiversity net gain assessment that our consultant use when assessing a development to measure biodiversity. 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 implications 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 development 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 land 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 about 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.

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.

Biodiversity net gain offsetting is a conservation strategy in which new developments or activities that result in the loss of biodiversity are offset by creating or enhancing irreplaceable habitats for wildlife in other areas. This approach aims to achieve a net increase in biodiversity overall rather than simply trying to mitigate the impacts of development.

This is often achieved through the creation or restoration of habitats, such as wetlands or woodlands, or through the introduction or reintroduction of native species. The goal of biodiversity net gain offsetting is to ensure that development and economic growth can continue while also protecting and enhancing biodiversity.

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 biodiversity 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 will now request all developers to achieve a minimum of 10% biodiversity before planning permission can be granted. A provision for secondary legislation has also been put in place from the act. This will set a date in which the mandate will become mandatory.

The mandate is predicted to be enforced in late 2023. The Act provides a two year transition period for authorities to get their regulations and policies in place before BNG becomes mandatory.

The Local Policy requires developers to adhere to certain standards in order to ensure biodiversity gain. Specifically, developers must demonstrate a minimum of 10% biodiversity net gain (BNG) through their schemes, as measured by the Biodiversity Metric 3.1. This will be achieved through the production of detailed Landscape Planting Schemes, Landscape Management Plans and Monitoring assessments for on and/or off-site.

A mitigation hierarchy must be followed to avoid, minimise or compensate any negative impact on biodiversity. Developers must also guarantee that the biodiversity gain is maintained for at least 30 years and adhere to “local nature recovery strategies” that encourage habitat creation and enhancement in the right places. Conservation covenants and a national register of land used for biodiversity gain will also be implemented. Other ecological legislation and policies still apply.

The goal is for developers to consider mandatory BNG during the initial land acquisition stage in order to avoid changes to designs and potential delays and costs during the planning application process.

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.

How can Collington Winter assist with biodiversity net gain?

Increasing biodiversity net gain within your proposed development project will help to increase its chances of obtaining planning permission from your local planning authority. If biodiversity is not achievable on site, biodiversity offsetting can be used to meet BNG requirements.

Our biodiversity consultants can assist with this process and keep you up to date with the legislation surrounding biodiversity net gain to ensure that your development project runs as smoothly as possible.

Our team can assist developers in meeting biodiversity requirements through habitat banking and biodiversity net gain offsetting. Our guidance can help to ensure that your project secures BNG for 30 years as is required for future developments, especially those located near sites of special scientific interest.

At Collington Winter, our consultants have vast experience in BNG, meaning that we can support our clients every step of the way. To find out more about biodiversity net gain offsetting, please get in contact with a member of our team today.

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