Biodiversity Net Gain Principles: Understanding BNG

Biodiversity net gain refers to the process whereby a development (or project) considers the environmental impact in terms of biodiversity. It aims to ensure that biodiversity is left in a better state than before.

Biodiversity Net Gain (BNG) is being requested more frequently by Local planning authorities to inform a planning application. The aim is to demonstrate how the proposed development will be of benefit to biodiversity in a measurable manner and counteract any biodiversity losses.

Utility providers, transport and other natural capital organisations are introducing Biodiversity Net Gain to internal policies. These policies will ensure any project will achieve a net gain, and even some are even setting gain targets of more than 10%.

Biodiversity net gain can also be used alongside an ecological impact assessment when determining the effect a proposed development may have on the surrounding environment.

biodiversity net gain principles

Biodiversity Net Gain Principles

According to the Chartered Institute of Ecology and Environmental Management (CIEEM), there are 10 crucial good practice principles of biodiversity net gain. These should help to achieve BNG if they are followed accordingly. The mandatory biodiversity net gain principles include the following:

·        Utilise the mitigation hierarchy to minimise the impact on biodiversity

·        Eliminate any negative impacts on biodiversity

·        Communicate each BNG outcome with complete transparency

·        Cover all areas of sustainability, including societal and economic factors

·        Involve any pre-development and post-development stakeholders in creating mandatory net gain solutions

·        Focus on producing long-term environmental benefits from BNG

·        Understand the variable factors and potential risks in order to achieve biodiversity and deliver net gain

·        Offer nature conservation that exceeds the stated BNG requirements

·        Determine a suitable method in order to secure measurable biodiversity net gains

·        Ensure the best possible results from biodiversity net gain

For case studies and a practical guide on biodiversity net gain principles, visit the CIEEM website.

Our team has strong experience completing biodiversity net gain and will provide guidance throughout the planning system process, from the initial land purchase agreements to monitoring assessments.


Calculating biodiversity net gain

Metrics assign every habitat on a site a ‘biodiversity unit value’ according to its relative importance for biodiversity. This enables comparison between the existing value of a site and what will be delivered through development or management, 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.

The Environment Act

The Environment Bill was passed this year, and BNG will soon become mandatory through the forthcoming Environment Act in 2023. However, the National Planning Policy Framework also requires a net gain approach which should be achieved in a measurable way.

Biodiversity net gain assessment

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

Project Feasibility

  • Identifying implications for potential development projects.
  • Audits of land for biodiversity gain capacity at the land acquisition stage.
  • Providing advice on options for delivery of biodiversity gain on and off-site or potential unit costs to the Local Planning Authorities.


Assessment and design

  • Baseline survey and habitat condition assessment – to provide data for the biodiversity metric (completed as part of a Preliminary Ecological Appraisal).
  • Detailed design-phase input: aim to retain highest valued ecological features, scope for habitat creation and enhancement.
  • Combining green infrastructure, SANG and habitat provision.
  • GIS expertise: managing metric data and supporting calculations.

Planning permission and delivery

  • Planning conditions: working with a project team (especially landscape teams) with the aim to provide feasible, proportionate and practical final designs and management.
  • Preparing long-term site management plans (or consult with Landscape Architects) and advising on future monitoring commitments.
  • If offsetting is required, we will liaise with local authorities, conservation organisations, and other third parties for agreeing the delivery of biodiversity gain.

How can Collington Winter assist with biodiversity net gain principles?

Our team of ecologists and landscape architects have helped numerous clients over the years. We have provided policy guidance for biodiversity gain in England, which varies across each Local Planning Authority across the country. 

Please get in touch if you would like further information about delivering 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 by implementing BNG.

Our Ecology Director, Olivia Collington, holds a Natural England license. If you would like to find out more about the services we provide, feel free to contact us using the details below.

Contact Us

Registered Address

23 Bark Street East, 1st Floor, Bolton, BL1 2BQ

Cambridge Office

Future Business Centre, Cambridge Campus, Kings Hedges Road, Cambridge, CB4 2HY


Head Office: 01204 939 608

Dumfries Office: 01387 378208

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