Biodiversity Net Gain Metric 4.0 – What you need to know

The Biodiversity Net Gain (BNG) metric 4.0 is a tool used to measure the change in biodiversity at a development site before and after the project, with the ultimate objective of leaving the environment in a measurably better state. This specific calculation, known as BNG metric 4.0, helps quantify the increase in biodiversity units resulting from the development. It replaced the previous version of the biodiversity metric 4.0, in March 2023.

The BNG metric 4.0 assesses the ratio of the habitat created or enhanced on-site to the habitat lost due to the development. This ratio takes into account both the quantity and quality of the habitat, aiming to increase both factors and achieve a net gain in biodiversity.

The update to the BNG metric includes improvements to the calculation tool, user guides, and condition assessment sheets.

In the UK, BNG metric 4.0 is now a requirement for certain types of development projects under the Town and Country Planning Act 1990. It is part of a sustainable development approach that promotes positive environmental impact and contributes to the protection and enhancement of biodiversity.

BNG planning conditions

The Environment Act 2021 and the national planning policy framework (NPPF) require that planning applicants, with a few exceptions, deliver a minimum of 10% BNG to obtain planning permission. This legal requirement will come into effect in November 2023.

The Biodiversity metric 4.0 will be used to measure this net gain, and all types of habitats must be maintained for a minimum of 30 years. According to the record published by Natural England, the BNG metric 4.0 will be recommended to the Secretary of State as the basis for the mandatory BNG required by the Environment Act 2021.

Implementing BNG

If you are unsure about how the mandatory BNG requirement may affect your planning application, it is recommended to contact your local planning authorities to discuss your plans in detail and ensure they align with BNG standards. If your project is likely to be impacted, it is best to consult with a skilled ecologist as soon as possible.

Our team of ecologists can assess your development plans to determine if they meet the necessary standards and suggest any measures required to comply with biodiversity regulations. With extensive experience in completing BNG, we can provide guidance throughout the planning process. Our expert ecologists can also visit your development site, prepare BNG plans, required BNG reports, and offer technical consultations.

We perform a habitat classification assessment, and the data collected is used to measure changes in the natural environment before and after development using the Defra Metric 4.0. We employ landscape planting and land management plans to determine post-development biodiversity measures.

Calculating 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 a standardised biodiversity metric 4.0 calculation, which takes into account factors such as habitat quality, rarity of species, and connectivity with other habitats. For the small sites metric, biodiversity metric 4.0 is simplified.
3. Calculate the net gain in biodiversity. Measuring biodiversity net gain 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.

How can Collington Winter assist?

Our team of biodiversity consultants are experts in the field of BNG planning law and can keep you up to date with new and changing legislation. Our consultants are experienced in using the biodiversity net gain metric 4.0 calculation tool, so you can be assured your biodiversity plans are accurate.

Our team’s experience and qualifications in BNG means that we can support our clients pre and post development in order to reach the required mandatory BNG bracket that is becoming law in late 2023.

If you require a consultation on the biodiversity metric system, or to find out more about our other services, get in touch today.