Biodiversity Net Gain: An introduction

Biodiversity Net Gain: an introduction

Updated: February 2024

Overview

The Government is preparing to introduce biodiversity net gain (BNG) as a condition to get planning permission for new development in England from 12 February 2024.

You will need to demonstrate that your development increases biodiversity by at least 10%.

You should plan for BNG now, because sites you are preparing will need to meet the requirements of BNG if your application for larger sites is submitted after 12 February 2024, or after 2 April 2024 for small sites.

The objective of BNG is to provide new homes for the people who need them while protecting and improving nature at the same time. Find out more about the benefits of BNG.

When net gain applies

You will need to demonstrate BNG for any planning application submitted after 12 February 2024, and for small sites after 2 April 2024.

Small development sites are defined in the Natural England Small Sites Metric (JPO40)

There are expected to be exemptions in certain situations, including: permitted development, householder applications, development of specific types of ownership that may be disproportionately impacted by the requirement (such as residential self-build), and brownfield sites that meet specific criteria.

What level of net gain must you achieve

You will need to show that your development will result in a measurable increase in biodiversity of at least 10%.

The percentage increase is the total of:

the biodiversity within the red line boundary after development compared to the level before development
biodiversity gains off the site that are registered against the development
biodiversity credits bought for the development from the Government.

In some cases the Local Planning Authority may ask for a higher percentage than 10%.

What steps you must take to demonstrate net gain

You must follow these steps to comply with BNG on your site:

calculate the biodiversity value before and after development using the biodiversity metric.
create a BNG plan - a document that explains how a project follows the mitigation hierarchy and achieves BNG. You can use the template provided by the Government.
submit your metric and biodiversity plan
deliver the agreed habitat improvements to the required standard for a minimum of 30 years. Onsite delivery will be secured through planning conditions. Landowners will be legally responsible for offsite provision.

How to calculate biodiversity value

You must use the biodiversity metri c to measure biodiversity value before and after the development, including for gains provided offsite.

The biodiversity metric calculates an area’s biodiversity value in units. Biodiversity units are based on habitat size, quality, type and location.

You can use the small sites metric for small development sites with little pre-existing biodiversity value. The simplified metric is designed for use by non-ecologists.

Find out more about calculating your metric.

You should hire an ecologist to calculate the metric or check calculations you have made.

How you can use units and credits

You must apply the mitigation hierarchy which means first mitigating losses at the site before considering gains off site.

You can either:

register units yourself
buy units from someone who has registered them against the development on your behalf

Where you use offsite biodiversity units towards your biodiversity gain you must do both of the following:

agree the habitat enhancement under the terms of a planning obligation or conservation covenant
record the enhancement in the biodiversity gain site register

You will only be able to buy credits from the Government as a last resort when onsite and local offsite provision of habitat cannot deliver the BNG required.

When to consider net gain in your design and build

You should think about how to include biodiversity from the earliest stage of your development. Include BNG when you make decisions about:

choosing land to build on, for example avoiding large woodland areas and protected sites
planning your design and build, so you do not lose biodiversity value during construction
what you spend money on, for example where and how you can achieve BNG
how you minimise, mitigate or compensate for environmental harm (otherwise known as the mitigation hierarchy)
how you or someone you employ will monitor, report and manage the biodiversity of the site long-term (otherwise known as a net gain agreement)
how you work with landowners if you do not own the land yourself
developing contracts with management companies

Get help and support

Get support from an ecologist

You should get ecologist help at least to:

prepare you BNG plan
calculate the metric

Your ecologist can also advise you throughout the process.

Find an ecologist consultant via the Chartered Institute of Ecology and Environmental Management’s directory

Find out more about biodiversity in your area:

your local planning authority
local environmental organisations, for example, your local Wildlife Trust
the Association of local environmental records centres