Collington Winter Environmental

Biodiversity Net Gain In Planning and Development

Call For an Initial Discussion

01204 939 608

Or Send a Message

What is biodiversity net gain (BNG)?


Biodiversity Net Gain is an approach to development that aims to leave the environment in a better state than it was before the development project took place. Previously, planning policy has encouraged UK construction and developments to achieve “no net loss” for biodiversity.

However, over the years, biodiversity has declined in the UK, and as such, the BNG initiative was launched to leave nature in a measurably better state. Overall, there has been a positive response to the consultation from ecological consultants, developers, and landscape professionals.

Biodiversity Net Gain (BNG) is being requested more frequently by Local planning authorities to inform planning applications. The aim is to show how the proposed development will be of benefit to biodiversity in a measurable way.

BNG also acts as a planning condition as well as a policy requirement for planning consent. It can therefore, have a significant impact during the decision making process of planning authorities when they debate whether to grant or refuse a planning application.

Is biodiversity net gain mandatory?

Following the passing of the Environment Bill, the Environment Act received Royal Assent in England in November 2021. Mandatory biodiversity gain for developments in England will be introduced through the Act. There is a two-year transition period before the net gain requirement becomes law (in autumn 2023).

The current national policy in England, The National Planning Policy Framework (NPPF) Paragraph 179 states:

“To protect and enhance biodiversity and geodiversity, plans should:

  1. b) … identify and pursue opportunities for securing measurable net gains for biodiversity.”

Paragraph 180 states:

“When determining planning applications, local planning authorities should apply the following principles: … opportunities to improve biodiversity in and around developments should be integrated as part of their design, especially where this can secure measurable net gains for biodiversity…”

Numerous Local Planning Authorities have been requesting the assessment for numerous years. Many have introduced or are currently amending local developers plans to ensure it is mandatory as a part of Local Policy.

The Environment Act and biodiversity net gain requirements

The Environment Act will introduce mandatory biodiversity net gain from Autumn 2023 onwards. The Act will require the following key points:

  • Developers must deliver BNG to a minimum of 10% net gain through their schemes; this will be measured through a metric, currently Metric 4.0.
  • A developer will be required to demonstrate how they will deliver biodiversity net gain by creating or enhancing habitats. Implementing BNG can be demonstrated through the production of detailed Landscape Planting Schemes, Landscape Management Plans and Monitoring assessments for on and/or off-site.
  • A mitigation hierarchy is to be followed and demonstrated to avoid, minimise or compensate. If it is not possible to compensate on the development site, then offsetting will be required elsewhere. This will be done through discussions of third party land owners, the council, landbanks or wildlife charities.
  • Developers will have to guarantee the biodiversity gain is maintained for at least 30 years (as outlined in Landscape Management Plans).
  • New “local nature recovery strategies” will be prepared to geographically cover England by “responsible authorities”; this will encourage habitat creation and enhancement in the right places.
  • Conservation covenants will be a mechanism used to deliver this (this approach is in preparation by Defra and Natural England).
  • A national register of land used for biodiversity gain will be established; this will involve setting up a new biodiversity credits market.
  • Metrics are only concerned with habitats and do not take protected species into consideration.
  • Other ecological legislation and policies still apply.


The aim is to get clients to think about biodiversity during the initial land acquisition and design stages and avoid retro-fitting the calculation once designs have been produced. Retrofitting will often lead to delays, unpredicted financial costs and difficulties with planning application determinations.

How to calculate biodiversity net gain

‘Biodiversity unit values’ will be assigned by metrics to every habitat on a site according to their relative importance for biodiversity. Comparisons can then be made between the existing value of a site and what will be delivered through development or management and post development. This may include an increase in natural habitats through retention and enhancement and/or creation, which goes over and above the environmental habitat originally on site.

Biodiversity net gain can be calculated through the DEFRA biodiversity metric 4.0, which requires a limited number of factors. These factors include:

 The type of habitat (both on and off site)

  • Any locations (if they are local environment priorities)
  • The size of habitat parcels in kilometres or hectares
  • The condition of any habitat parcels

 The government website also provides a biodiversity metric 4.0 calculation tool which can help to determine your biodiversity unit score that translates into the standards of your local planning authority.

How we can assist

Our team of ecologists and landscape architects have helped numerous clients over the years, including policy guidance for biodiversity gain in England. It is important to note that this varies across each Local Planning Authority in the country. Biodiversity is something that we are qualified and experienced in, and we can offer advice on your development project. We are determined to offer you the support you need in order to reach the required mandatory biodiversity bracket.

There are three stages of using the assessment, and we assist our clients during the very early stages of development, including promotions and land purchases. We are happy to complete an informal initial assessment for sites of interest. This helps our clients understand the probable implications and costings of Biodiversity Net Gain from the offset.

Please get in touch if you would like further information about Biodiversity Net Gain or Landscape Management Plans. We are happy to offer free CPD sessions on the Biodiversity Net Gain Principles and how we can help your schemes achieve this.

Registered Office

23 Bark Street East, 1st Floor, Bolton



01204 939 608


Get in touch

Get in touch
close slider
Please enable JavaScript in your browser to complete this form.