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Biodiversity Net Gain Guidance: Understanding BNG

Biodiversity net gain (BNG) refers to the process in which a development project considers the environmental impact in terms of long term biodiversity. BNG aims to leave the natural environment in a measurably better state than it was previously.

Biodiversity Net Gain is now frequently being requested by local authority to inform an application for planning permission. The aim is to demonstrate how proposed development projects will benefit biodiversity net gain. This also helps to track the environment in a measurable manner and counteract any losses of biodiversity.

Transport, utility providers and other natural capital organisations are beginning to introduce Biodiversity Net Gain to internal policies. These policies will help to ensure that any development project will achieve biodiversity net gain. Some organisations are even setting gain targets of more than 10%.

Biodiversity net gain can also be effective alongside ecological impact assessments. This is because BNG can help when determining the effect a proposed development project may have on the environment surrounding it.

biodiversity net gain principles

Biodiversity Net Gain Guidance: Achieving BNG

According to the Chartered Institute of Ecology and Environmental Management (CIEEM), there are ten crucial good practice principles of biodiversity net gain. These principles should help to achieve biodiversity net gain if they are followed accordingly. These 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 net gains for biodiversity
  • 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.


The Environment Bill

The Environment Bill was recently passed this year. This bill will make biodiversity net gain become mandatory through the forthcoming Environment Act in 2023. However, the National Planning Policy Framework from the Government also requires a net gain approach from developments in England. This should be achieved in a measurable way using BNG metrics.

Mandatory Biodiversity Net Gain

The Environment Act received Royal Assent in England in November 2021. This act introduces a requirement to deliver biodiversity gain for proposed developments in England. There is, however, a two-year transition period before the net gain requirement becomes law (in autumn 2023).

This environment act will require the following key points:

  • Developers must deliver a minimum of 10% net gain through their schemes. This will be measured through a metric, currently Metric 3.0.
  • A developer will need to demonstrate how biodiversity gain will be delivered. This will be demonstrated through the production of detailed Landscape Planting Schemes, Landscape Management Plans and Monitoring assessments.
  • 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 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 irreplaceable habitats and do not take protected species into consideration.
  • Other ecological legislation and policies still apply.

How can Collington Winter assist?

Our team of ecologists and landscape architects have vast experience completing biodiversity net gain for instructing clients. We are able to provide biodiversity net gain guidance throughout the planning process, from the initial land purchase agreements to monitoring assessments.

Our team of ecologists are also able to complete habitat classification assessments from which the data is entered into a biodiversity metric to measure any changes to the environment. This includes pre and post development stages of development. Landscape management plans and planting plans are also used to inform post development measures.

Please get in touch if you would like further information regarding Biodiversity Net Gain guidance or Landscape Management Plans. If you are interested in the ecological services we provide, contact us using the form below. You can also get in contact with our Ecology Director, Olivia Collington, via email at

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