Understanding biodiversity net gain

1st August 2023

Biodiversity net gain (BNG) is development that leaves biodiversity in a better state than before.

In England, under the Environment Act 2021, delivering at least 10% BNG becomes mandatory for all relevant Town and Country Planning Act developments from November 2023. It will become mandatory for smaller sites in April 2024 and for nationally significant infrastructure projects in November 2025. Scotland and Wales have adopted their own approaches to net gain (‘enhancement’ and ‘net benefit’ respectively), where some of the principles of tackling biodiversity loss and improvement are similar but they have not adopted the same use of metrics.

Why is BNG important?

Biodiversity is the variety of life. We depend on it and benefit from it as a species, but our actions are also accelerating the decline in biodiversity loss. More than ever, we need to help halt the decline and turn it into a net gain for the benefit of people, places, species and our planet itself. The global deal for nature at the UN Biodiversity Conference, COP15, in Montreal in December 2022 made the case for more urgent action and now, collectively, we need to respond to this.

The apex goal of the UK’s 25-year environment plan is to improve nature so we can have ‘thriving plants and wildlife’. BNG is a tool for achieving this. Successful delivery of BNG needs to link up with the principles of the Nature Recovery Network to make our habitats ‘bigger, better and more joined up’, as advocated in the Lawton Review. It needs joined-up thinking between developers, local authorities, landowners, local nature partnerships and other stakeholders to support joint priorities for nature. Fundamentally, implementing measures to deliver net gain successfully will increase the quantity and/or quality of natural capital and therefore can deliver gains in ecosystems services.

What are the challenges?

Not surprisingly, there are many concerns and challenges in the implementation of BNG. One of the biggest challenges is how BNG is interpreted and applied; another is the shortage of resources for local planning authorities to deliver BNG, as well as a shortage of ecologists generally.

Application of the mitigation hierarchy is critical to the successful implementation of BNG. The challenge is to get this right and ask, for example, ‘how nature-positive is this development going to be and can it meet or exceed the BNG requirement?’.

Confidence in the BNG process will grow over time and the challenges will diminish through experience and sharing best practice.

Preparations for BNG

During the past year, the IEMA Biodiversity and Natural Capital (BANC) Steering Group has run a series of events on BNG to help IEMA members and practitioners prepare for it. We have created a Biodiversity and Natural Capital Buzzword Guide, which defines and explains key biodiversity and natural capital terminology. It was one of IEMA’s most popular downloads last year.

In the first half of 2023, IEMA held a series of BNG webinars focused on the three stages of the BNG process:

  • BNG baseline and design
  • BNG implementation and stakeholder engagement
  • BNG management and monitoring.

The output of these webinars has been put into a Good Practice Insights paper for practitioners and members.

To download a copy of Biodiversity Net Gain – Good Practice Insights, visit bit.ly/3DqPJ9j

The Biodiversity and Natural Capital Buzzword Guide is available at bit.ly/44W4PiE

Louise Dunkerley MIEMA CEnv is an associate director at Ecus and a member of the IEMA Biodiversity and Natural Capital Steering Group

BNG in action

Biodiversity Net Gain – Good Practice Insights has been developed to help provide practical examples of BNG, in practice, in England. It follows the BNG webinar series and summarises each case study presented, giving an overview of the project as well as details of the outcomes and challenges faced during the project, and tips and advice on specific tools and techniques used during each project. It highlights what worked and what was challenging and attempts to answer frequently asked questions under each of the BNG stages. It provides some great examples of partnership working. A list of useful resources for further information on BNG is also included in the paper.

BNG is both the start of and part of the rapid development of biodiversity-related policies, regulations and actions that environmental and sustainability professionals are having to adjust to. Although there are challenges, this is a great opportunity for us to act and make a professional contribution to the nature crisis by working to implement BNG successfully.


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