Biodiversity Net Gain

What is Biodiversity Net Gain?

Biodiversity Net Gain is defined by the Department for Environment, Food & Rural Affairs as:

“an approach which aims to leave the natural environment in a measurably better state than beforehand.”

It encourages developers to include biodiversity improvements through habitat creation or enhancement, as well as avoiding or mitigating harm. In order to maximise net gain for biodiversity, developers have to   work with stakeholders to support local biodiversity goals.

Is Biodiversity Net Gain compulsory?

Biodiversity Net Gain has become mandatory through the Environment Act 2021. It is a vital part of securing planning consent in England and local authorities have adopted the requirements as part of their planning policies.

New developments are required to demonstrate a minimum of 10% increase in biodiversity on or near their application sites for at least 30 years.

Many developers are making changes to adapt to these requirements to put themselves ahead of the competition.

Ecological appraisals and survey reports have been a requirement of planning applications for many years – these show that mitigation or avoidance of harm to key habitats and protected wildlife as well as enhancement measures have been included in the development plans, and that the work complies with wildlife laws and policies. There have also been schemes such as BREEAM, HMQ and CEEQUAL that evaluate environmental and sustainability criteria (including wildlife).

Each local planning authority can use its own framework to assess and enforce biodiversity net gain. However, the new Environment Act makes this the first specific legal duty for development to improve biodiversity.

Some types of development are exempt from the Biodiversity Net Gain criteria:

  • Building extensions
  • Certain urban brownfield sites
  • Major infrastructure projects and marine sites
  • Smaller developments with less than 10 residential units or an area below 0.5 hectares

How do I prove Biodiversity Net Gain at my development?

Local planning authorities require new planning applications to include Biodiversity Net Gain calculations to prove there will be biodiversity improvements.

This proof needs to include:

  • Written documentation and clear maps showing the assessment of net gain for biodiversity to submit with planning applications including the completion of the DEFRA Biodiversity Metric 2.0: Calculation tool
  • The level of net gain for biodiversity currently acceptable in the local planning authority area
  • The measures to achieve 10% net gain for biodiversity onsite or alternative compensation measures
  • Financial support for 30 years positive biodiversity management (through a s106 or similar agreement)
  • A Design & Access Statement explaining the derived Biodiversity Net Gain
  • Proof that an ecological consultant has advised on the mitigation hierarchy, avoidance of damage, and a net gain assessment or compensatory off-site solutions.

You will need to appoint an Ecological Consultant at the earliest stage possible. They will work closely with the Landscape Architect and Urban Designers to ensure that the best possible solutions to achieve Biodiversity Net Gain are considered from the very start.

How is Biodiversity Net Gain calculated?

In simple terms, the calculation compares the pre-development ‘baseline’ habitat biodiversity value with the post-development biodiversity value. It takes into account habitat losses, retention, creation and, where possible, enhancement.

But the technical knowledge behind this is much more complex, and your Ecological Consultant will have several tasks to complete to get an accurate figure, such as:

  • Surveying the application area habitats prior to development identifying habitat type and condition (this should include any off site compensation areas)
  • Assess the proposed ecological and landscape design commitments after development
  • Calculate the biodiversity units before and after development using the biodiversity metric. Off-site compensation and/or credits can be added to the calculations
  • Calculate percentage Biodiversity Net Gain or net loss.

Achieving Biodiversity Net Gain

When we make our assessment, we take into account a multitude of criteria, such as habitat distinctiveness, its condition, its local and regional significance, and its connectivity to other habitats. It’s important we follow the latest guidelines from professional bodies and Defra, as well as making sure the interpretation meets with the local planning authority expectations.

Generally, habitat creation or enhancements which contribute to net gain will only be accepted if they are in areas accessible by the public or residents of the development – for example, there is no guarantee that measures such as creation of habitats in private gardens will be retained in the long-term, so they cannot be included in the calculations.

What if I cannot achieve Biodiversity Net Gain?

If net gain for biodiversity isn’t achievable, and losses are unavoidable, then offsite compensation or ‘biodiversity credits’ might be acceptable. Both measures require good technical evidence.

Off-site compensation delivery is the full responsibility of the developer, and you will need to provide full costs for this and provide the funding.

If Biodiversity Net Gain isn’t possible at the site of the development, you may be able to buy additional land, or buy land from a ‘habitat bank.’ However, it’s always preferred that measures are taken at the original development site as much as possible.

For more information about Biodiversity Net Gain and how to incorporate it into your scheme design, get in touch with us on 01225 459564 or email

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