In July 2019, Defra’s summary of responses and the government response  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  which consolidates much of the literature and opinion on BNG that has preceded its inclusion in the Bill.
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.
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:
In July 2019 Natural England published a revised and updated Biodiversity Metric  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.
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.
Targets for BNG should be integrated into project planning and delivery and the following sequential steps indicate how this can be achieved.
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: