The Solent Forum

Working in parnership for the future

Biodiversity Net Gain

Biodiversity Net Gain is an approach to development that seeks to leave biodiversity in a better state than before. Where a development has an impact on biodiversity it encourages developers to provide an increase in appropriate natural habitat and ecological features over and above that being affected. It is hoped that the current loss of biodiversity through development will be halted and ecological networks can be restored. It still relies on the application of the mitigation hierarchy to avoid, mitigate or compensate for biodiversity losses. It is additional to these approaches, not instead of them. It uses a metric as a proxy for recognising the negative impacts on habitats arising from a development and calculates how much new or restored habitat, and of what types is required to deliver sufficient net gain.

The Environment Bill will make it mandatory for housing and development, subject to some narrow exemptions, to achieve at least a 10% net gain in value for biodiversity – a requirement that habitats for wildlife must be left in a measurably better state than before the development. Developers must submit a ‘biodiversity gain plan’ alongside usual planning application documents. The local authority must assess whether the 10% net gain requirement is met in order to approve the biodiversity gain plan. If net gain is not achievable on-site, the biodiversity net gain plan will need to include off-site habitat enhancements, in line with the mitigation hierarchy; the local authority must be satisfied that this is secured through a planning obligation or conservation covenant. 

Government planning policies for biodiversity are set out in the National Planning Policy Framework (NPPF), while the Local Authority’s local plan will set out how they address these requirements in local policy terms. LPAs need to be able to understand what the potential impacts of the development might be and if there are impacts on biodiversity, how these will be avoided, mitigated, or compensated.

Proposed BNG Timetable

Summer 2021:

Autumn 2021:

Spring 2022:

Spring 2023:

Autumn 2023:

What is Environmental Net Gain?

‘Environmental Net Gain’ is a term that covers multiple environmental benefits. Whilst ENG does not yet have a single agreed definition, in Defra’s public consultation on Biodiversity Net Gain (BNG) it was defined as: “In short, this means improving all aspects of environmental quality through a scheme or project. Achieving environmental net gain means achieving biodiversity net gain first, and going further to achieve increases in the capacity of affected natural capital to deliver ecosystem services and make a scheme’s wider impacts on natural capital positive.” 

Chichester Harbour Protection and Recovery of Nature

To ensure the best outcomes for Chichester Harbour, the Conservancy have formed a steering group with the Environment Agency, Natural England, Sussex IFCA, and Coastal Partners to protect, restore, and deliver ‘net gain’ for nature. This will help plan, coordinate and manage work over the next 10 – 25 years. This initiative should enable it to source new funds, increase ‘blue’ investments, and bring the wider community together to deliver a programme of actions. The initiative known as Chichester Harbour Protection and Recovery of Nature (CHaPRoN for short) will focus on priority habitats such as saltmarsh, seagrass, and oysters, as these are at the biggest risk of further loss, have a high natural capital value, and are great at carbon fixing. The ambition is wider though and will seek to create wildlife recovery areas stretching from Langstone Harbour in the West to Pagham Harbour in the east and linking terrestrially to the South Downs National Park a mile to the north of Chichester Harbour AONB.


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