Biodiversity and planning application requirements

Biodiversity is the variety of all living things on our planet, from species, habitats and ecosystems. Biodiversity Net Gain (BNG) is an approach to planning and development management that leaves the natural environment in a better state than it was before.

Policy 34 in our City Plan focuses on Green Infrastructure. It requires developments to achieve biodiversity net gain, wherever feasible and appropriate, and to maximise opportunities to enhance existing habitats and create new habitats for priority species. This is supported by guidance in our Environmental SPD

The Mayor’s London Plan also requires new developments to make urban greening a fundamental element of their site and building design and to deliver net gains for biodiversity. Applicants should refer to London Plan Policy G6 Biodiversity and Access to Nature and G5 Urban Greening.

The Mayor has also published a Biodiversity Net Gain Design guide.

Natural England has produced advice for developers regarding the impact of development on protected species and habitats.

How is Biodiversity Net Gain measured?

BNG is calculated using a biodiversity metric, which measures the biodiversity value of habitats in ‘biodiversity units’ as a proxy for nature. The metric can be used to calculate how a development might change the biodiversity value of a site. It can help you to design and plan to support biodiversity better.

It compares the biodiversity value of habitats found on a site before and after development to determine if there is a loss or gain in biodiversity. You can read the guidance about using the biodiversity metric on GOV.UK.

To measure BNG and assess the impacts of planning applications, use the latest version of Defra’s Biodiversity Metric. 

Other requirements to protect important habitats and species must be achieved alongside providing BNG.

Biodiversity and planning application requirements

Our validation requirements currently require a biodiversity survey and assessment of whether a proposed development is on or close to a Site of Importance for Nature Conservation (SINC) and would impact a priority species or habitat, or another ecological feature outside the SINC network. You can see designated sites on our interactive policies map.

Applications that may trigger the requirement for a biodiversity survey and assessment include:

• proposals within 50 metres of woodland, water, Sites of Importance for Nature Conservation, field hedgerows or lines of trees with obvious connectivity to woodland or water
• proposals affecting bridges, tunnels, air raid shelters, cellars and underground ducts and structures
• proposals involving the lighting of churches, listed buildings and open spaces
• proposals affecting trees, woodland and hedgerows
• proposals affecting derelict land, allotments and railway land
• proposals affecting buildings, structures, features or locations where protected species (including bats, hedgehogs and various birds, invertebrates and plant species) are known to be present

An Urban Greening Factor Assessment is also required for all major applications and a landscaping strategy and details may be required for other proposals. See our Validation List for more information.

New planning requirements from 2024, mandatory BNG

The Environment Act 2021 introduces new requirements that all planning permissions granted in England (with a few exemptions) must deliver at least 10% biodiversity net gain, using the metric developed by DEFRA that generates a biodiversity value for a site before and after development to demonstrate this. Secondary legislation and associated guidance have now been published and sets out that

• mandatory BNG will apply to major development from 12 February 2024 onwards and minor development from April 2024 onwards
• householder development will be exempt from mandatory BNG, along with permitted development and proposals which have a very small (less than a 25-metre squared area or five-metre length) or temporary (under two years) biodiversity impacts
• relevant developments will be subject to a general pre-commencement planning condition. This planning condition will require that developers submit and have approved by the council a ‘biodiversity gain plan’ before any works can begin
• the ‘biodiversity gain plan’ describes how the developer will achieve a 10% BNG, informed by a biodiversity metric assessment. There is a standardised template for the ‘biodiversity gain plan.’
• If 10% BNG cannot be achieved within the red line boundary of the planning approval, offsite habitat creation will need to be relied upon. The ‘biodiversity gain plan’ will need to evidence this.

The government has published a draft National Planning Practice Guidance on Biodiversity Net Gain. 

See more detail on our validation requirements - Biodiversity Net Gain Requirements | Westminster City Council.