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Biodiversity Net Gain Credits: What are they?

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Biodiversity net gain (BNG) is a concept in conservation biology that refers to the net increase in biodiversity that results from a development project. This means that the project should not only avoid negative impacts on habitats and biodiversity, but should also actively contribute to increasing the diversity of species and habitats in the area, ultimately delivering biodiversity net gain. Once implemented, BNG aims to secure long term habitat creation and enhancement, which are to be maintained for at least 30 years.

By complying with the guidelines of biodiversity within their development plans, developers, project and land managers should have more chance of their planning permissions being granted, as this is up to each local planning authority to determine.

Biodiversity net gain can be achieved through various means such as creating new habitats, restoring degraded ones, or translocating species to new locations. The goal of biodiversity net gain is to ensure that development projects do not result in a net loss of biodiversity, and ideally lead to an overall improvement in the health and diversity of ecosystems. Local planning authorities require all permissions they grant to achieve at least 10% biodiversity following the Environment Act 2021.

The Environment Bill 2021 allows a transitional two-year period for local authorities to get their policies and processes smoothly in place before BNG becomes mandatory in 2023. The Act includes a provision for secondary legislation and the National Planning Policy Framework also requires a net gain approach which should be achieved in a measurable manner.

What is biodiversity net gain?

Mandatory biodiversity net gain (BNG) is an approach that seeks to increase the amount of biodiversity in a particular area as a result of a developed land. It involves ensuring that the development project results in a positive gain in biodiversity, meaning that the biodiversity in the area after the project is completed is greater than the biodiversity before the project began.

This approach typically involves an assessment of the existing biodiversity in the area before the project begins, as well as an evaluation of the potential impact of the project on biodiversity. Based on this assessment, measures are put in place to mitigate the negative impacts of the project on biodiversity and to create or enhance the biodiversity in the area to meet net gain requirement.

Biodiversity net gain is becoming increasingly important as a way to ensure that development projects do not harm the natural environment and that they contribute to the conservation and enhancement of biodiversity.

The Environment Act states the following key points regarding achieving BNG:

  • 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” (LNRS) 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.


What are biodiversity net gain credits?

Biodiversity net gain credits are a mechanism for incentivising and measuring biodiversity gains resulting from development projects. The concept of biodiversity net gain is based on the idea that development projects should leave the environment in a better state than before they began. Biodiversity net gain credits provide a standardised way to quantify and track the biodiversity gains resulting from development projects.

Biodiversity net gain credits work by assigning a credit value to different types of biodiversity gains, such as the creation of new habitats, the restoration of degraded habitats, or the enhancement of existing habitats. Development projects that generate a net gain in biodiversity can earn these credits, which can then be sold or traded.

The credit system is a way to encourage developers to prioritize biodiversity in their projects, and to ensure that the benefits of these projects are measurable and transparent. They can also provide a source of funding for biodiversity conservation and restoration initiatives.

How do you calculate BNG?

Biodiversity net gain (BNG) is calculated by comparing the biodiversity value of a site before development to the value after development, focusing on losses and gains of biodiversity.

To calculate BNG, the following steps can be taken:

1. Identify the baseline biodiversity value of the site before development. This can be done by conducting a habitat survey to identify the different habitats and species present on the site and their relative importance in terms of biodiversity.

2. Determine the biodiversity value of the site after development. This involves assessing the quality and quantity of the habitats that will be created or enhanced as a result of the development. The value of the habitats can be assessed using the standardized Defra biodiversity metric version 4.0, which takes into account factors such as habitat quality, rarity of species, and connectivity with other habitats. For small development sites, metric users can utilise the small site metric, which is a simplified version of the 4.0 metric.

3. Calculate the net gain in biodiversity. This is done by subtracting the baseline biodiversity value from the biodiversity value after development. If the biodiversity value after development is higher than the baseline value, the net gain will be positive.

4. Implement measures to enhance biodiversity on site if necessary to achieve a positive net gain. This may involve incorporating features such as green roofs, planting native vegetation, and creating wildlife corridors to improve habitat quality and connectivity.

It’s important to note that the biodiversity net gain metric 4.0 is a complex process that requires input from ecologists, planners, and other experts. It’s recommended that you work with a qualified professional to ensure that your calculations are accurate to achieve biodiversity gains.

Biodiversity net gain offsetting

Biodiversity net gain offsetting is essentially an act that ensures conservation measures are taken to further habitats and environments when biodiversity net gain is unable to take place elsewhere, ultimately compensating for the biodiversity loss in a measurable way.

As with many things, there are pros and cons to 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 preserving other natural habitats 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. 

How can we assist?

If you are a developer or land owner and are looking for more information surrounding biodiversity net gain credits then our team of experienced Ecologists are here to help.

We can ensure your project is conforming to the current legislation, saving you both time and money. Following the guidance and rules surrounding biodiversity net gain will help you gain the required planning permissions from your local authorities to carry out your project. 

Our team’s experience and qualifications in BNG means we can support our clients efficiently, calculating their pre development biodiversity measurements to ensure the required gain is made post development in order to reach the required bracket that is becoming law in late 2023. We can offer a range of services including consultations on site and off site, protected species surveys and expert advice and planning surrounding BNG.

To find out more how CWE can help you with your biodiversity net gain plans then please do not hesitate to get in touch with us to discuss your queries. Contact us on 01204 939 608 or use the online form below.


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