What is Biodiversity Net Gain

15.08.2019 6 min read

The Environment Bill, published in October 2019 [1] and given its first reading on the 30th January 2020, introduces mandatory biodiversity net gain (BNG) to ensure that new developments enhance biodiversity and help deliver thriving natural spaces for communities. This follows the change from a ‘No Net Loss’ to ‘Net Gains’ within the National Planning Policy Framework [2], with many local planning policy documents already reflecting this change in focus.

In July 2019, Defra’s summary of responses and the government response [3] sought views on whether to mandate BNG, and how a mandatory approach might be implemented most effectively. The responses have informed the POSTbrief 34:Net Gain [4] which consolidates much of the literature and opinion on BNG that has preceded its inclusion in the Bill.

What is biodiversity net gain?

BNG delivers measurable improvements for biodiversity by creating or enhancing habitats in association with development. Where development has an impact on biodiversity it encourages developers to provide an increase in appropriate habitats over and above that being affected.

Through the implementation of BNG in all projects, it is hoped that the current loss of biodiversity through development will be halted and ecological networks can be restored.

BNG is not a replacement for Environmental Impact Assessment, protected species surveys and other forms of biodiversity assessment that are required for many projects. Rather, it should be used in combination with these and other approaches to provide a holistic assessment.

What may mandatory BNG require of developers?

Having confirmed that it would mandate net gains for biodiversity in the Environment Bill, the government’s response provides further clarity on the key responsibilities for developers:

  • The requirement to achieve a 10% net gain in biodiversity will apply to the majority of developments, with narrowly-defined exemptions [5]
  • Opportunities to achieve net gain on-site must be fully explored to ensure that loss of biodiversity is avoided or minimised before options for offsite compensation are considered. This implements the ‘mitigation hierarchy’ [6] which is fundamental to the BNG approach, and ensures that biodiversity on site or in the local area is promoted
  • Inclusion of information on BNG for determining planning applications including baseline data, measures to avoid ecological harm and a forecast of BNG outcomes
  • Net gain outcomes, through habitat creation or enhancement as part of delivering mandatory BNG, must be maintained for a minimum of 30 years
  • where BNG cannot be achieved within a development site, developers will contribute to “local nature recovery strategies” which local authorities will be required to identif
  • If BNG cannot be delivered locally then developers will be able to invest in “nationally strategic habitats” with the purchase of government-provided “biodiversity credits”

How is BNG calculated?

In July 2019 Natural England published a revised and updated Biodiversity Metric [7] containing guidance and a calculation tool that provides a standardised approach for assessing BNG for developments.

The complexity of natural ecosystems means that it is impossible to fully characterise the biodiversity of a particular area. Therefore, the metric by which BNG is calculated is concerned with broad habitat types and not associated species. These habitats are defined using simple descriptors (referred to as ‘multipliers’). The biodiversity metric involves applying the multipliers to habitats present before and after development to calculate the number of biodiversity units in each case, and the difference in the number of units pre and post-development determines whether BNG has been achieved.

Principles for application of the metric, such as the aforementioned mitigation hierarchy, acknowledgment that some habitats are irreplaceable, and provision of habitats of greater value than those lost, all aim to reduce uncertainty and misapplication of the metric. Additionally, the post-development multipliers account for the risk and time taken to create new habitats.

Delivering meaningful net gain

BNG places clear emphasis on retaining biodiversity locally. The Local Nature Recovery Strategies, to be developed by local authorities, will ensure that BNG reflects local biodiversity priorities. The requirement to manage habitats created for BNG for 30 years emphasises the expectation for sustained gains at the project level and for cumulative beneficial effects.

Meaningful BNG creates habitats that provide all the resources for wildlife to thrive on-site and enriches the biodiversity of the surrounding area. BNG should be a consideration in place-making, the design of green infrastructure, managing the impacts of climate change, and increasing well-being. It is essential that habitat creation for BNG is of high quality to ensure it delivers synergistic benefits as part of multi-function landscape schemes and clearly adds value to a project.

This outlook Biodiversity net gain – green roof will foster acceptance of the additional considerations associated with mandatory BNG, and an appreciation of some additional benefits of high-quality multifunctional design, which include meeting targets required by other assessments such as BREEAM and Urban Greening Factor. A multi-functional approach to the landscape can substantially reduce the amount of land required to achieve BNG. It will also avoid the risk of BNG being seen merely as a target score to be achieved peripherally, with associated risks for planning consents, and of ineffective habitat creation and management.

How should developers engage with net gain in delivery of the development project?

Targets for BNG should be integrated into project planning and delivery and the following sequential steps indicate how this can be achieved.

  1. Establish awareness and understanding of BNG among all members of project teams.
  2. Engage an ecologist at an early stage in the development and seek advice on matters contributing to effective and sustainable BNG, including avoiding and minimising ecological harm and creating a landscape rich in biodiversity and green infrastructure.
  3. Obtain adequate pre-development baseline data, likely to involve an ecology survey of the site to record the types and condition of habitats present, and confirm pre-development biodiversity units.
  4. Develop an outline masterplan, and test design by calculating preliminary post-development biodiversity units.
  5. If necessary, revise master plan in response to the initial calculation and test subsequent iterations of the master plan.
  6. Prepare a landscape and ecology management plan or similar, to address requirements for ongoing management.
  7. Carry out compliance checks during and on completion of construction.
  8. Ensure clear handover of responsibility for maintenance from developer to the management company.
  9. Implement and monitor habitat management.
  10. Revise management plan if necessary, to ensure BNG is sustained.

Temple’s Ecology services

Temple offers expert advice that will maximise the smooth and cost-effective delivery of BNG.

We have experience of delivering net gain on projects ranging from major infrastructure schemes to small urban developments, and in resolving significant constraints to delivery.

Our specialist ecology teams are well equipped to provide services in relation to BNG, including:

  • initial advice to inform site selection and to establish options and feasibility for achieving BNG on-site and scope for off-site provision;
  • baseline surveys and condition assessments to inform outline design and provide data pre-development metric calculations for BNG;
  • design input, often as part of multi-disciplinary teams, to help create high quality schemes that deliver demonstrable benefits for biodiversity;
  • preparing and monitoring site-specific biodiversity management and maintenance plans; and
  • engaging with stakeholders and consultees involved in BNG including statutory bodies, planning authorities, and voluntary sector organisations.
[1] https://www.gov.uk/government/publications/environment-bill-2019/environment-bill-policy-statement#restoring-and-enhancing-nature-and-green-spaces
[4] http://researchbriefings.files.parliament.uk/documents/POST-PB-0034/POST-PB-0034.pdf
[5] The loss of irreplaceable habitats cannot be addressed though BNG and urgent Crown developments (or other developments specified by the SoS) are exempt
[6] NPPF Para 175 a) If significant harm to biodiversity resulting from a development cannot be avoided (through locating on an alternative site with less harmful impacts), adequately mitigated, or, as a last resort, compensated for, then planning permission should be refused
[7] http://publications.naturalengland.org.uk/publication/5850908674228224

Key Contacts

Dr Sarah Cox Divisional Director - Ecology