Keeping the Land Alive: Biodiversity Net Gain

Biodiversity net gain (BNG) is a concept that has gained significance in recent years, driven by the urgent need to protect and enhance our natural ecosystems during and after construction projects. Now in England it’s backed by legal requirements.

But what actually is Biodiversity Net Gain?

The core principle of BNG is simple: any new development must leave the biodiversity of a site in a better state than it was previously. Until the government passed the Environment Act in 2021, this was not a legal requirement. However, from February 2024 the act mandates that in order to obtain planning permission developers must put in place plans to increase the biodiversity value of their site by at least 10%. There are exceptions for those habitats deemed to be irreplaceable, such as those comprising of ancient trees, limestone pavement and coastal sand dunes. These are not subject to the minimum 10% biodiversity increase. Instead developers must establish an alternative to mitigate the impact on these important sites as set out under existing legislation. Planning permission for development resulting in the loss or deterioration of irreplaceable habitats will only be granted in exceptional circumstances.

Currently, the legislation only covers England. Scotland, Wales and Northern Ireland have yet to formalize BNG, but all are actively exploring biodiversity improvements through their respective National Planning Frameworks. BNG’s reach extends beyond residential housing, encompassing a broad spectrum of projects, including industrial and commercial. It applies to both major developments—those with ten or more dwellings or over half a hectare in size—and, as of April 2024, smaller developments too.

By making BNG mandatory the United Kingdom is taking crucial steps toward preserving our ecosystems for future generations, while also encouraging developers to consider the need to enhance the natural world at an early stage.

How does it work?

There are 3 ways a developer can achieve 10% BNG:

You can combine all 3 steps, but must follow the steps in order. This order of steps is called the biodiversity gain hierarchy.

The Biodiversity Gain Site Register serves as the central hub for tracking off-site gains. This prevents double counting and ensures transparency. Registering a site on the BNG Register costs £639, with subsequent allocations priced at £45.

On-site BNG provision by developers doesn’t require registration but must still be legally secured for at least 30 years after the completion of the development. The government aims to streamline information by extracting on-site data from planning permissions and integrating it into the BNG Register for easy accessibility. The enforcement of both off-site and on-site BNG is carried out by Local Planning Authorities.

What are the metrics for Biodiversity Net Gain?

A biodiversity metric is used by ecologists to measure changes in our in biodiversity by looking at specific properties of habitats. Biodiversity metrics assign a ‘unit value’ to each habitat on a site based on its relative biodiversity value, which allows comparison between the existing site value and what will be achieved through development or management. Protected species are not taken into consideration by biodiversity metrics.

The value of a habitat will be measured considering the following factors:

• Size
• Distinctiveness
• The diversity or rarity of the habitat and species found
• The strategic significance of a site and its ecological importance locally
• The condition and quality of the habitat
• The connectivity of the site and how the habitat is connected to other areas
• The local importance of the habitat site

How can I best practically deliver Biodiversity Net Gain?

Protect, don’t restore – A mantra common in conservation is “it is less costly to conserve nature than it is to restore it”. In relation to BNG this means your first steps should be avoidance – what can you do to reduce your ecological footprint during site works? A good baseline survey from an ecological consultancy will identify key biodiversity in the area, helping you to avoid bad publicity and costly alterations if your project is found to be disrupting an important local habitat.

Visual Marketing – As well as helping the environment, BNG can add value to a development in a way that looks great in plans and renderings, and because it’s supported by environmental science and monitoring people can have confidence that the designs will translate into reality over the long term.

Sustainable Habitats – If creating a new habitat, make one that will stand the test of time through ensuring its suitability for the surrounding ecosystem. Beyond just fulfilling obligations during construction, a lasting habitat will demonstrate your company’s environmental competency to future clients and investors, and connect your brand with green spaces for many years to come.

Learn more about this topic at:

• Biodiversity net gain | GOV.UK
• Make on-site biodiversity gains as a developer | GOV.UK
• What landowners can do now to gear up for the biodiversity net gain market | Natural England (blog.gov.uk)
• A Helpful Guide to Biodiversity Net Gain | Ecosulis
• Everything you need to know about biodiversity net gain | Ecology by Design
• Full costs of biodiversity net gain revealed | environmentanalyst.com