Biodiversity Net Gain Assessments

Biodiversity is the variety of life on earth; it includes all living things and the places in which they live. It is essential to sustain our society, well-being and economy.

Biodiversity in the UK and internationally is declining as it comes under increasing pressure from development and land management practices. Enhancing biodiversity is integral to sustainable development, and Biodiversity Net Gain (BNG) is an approach to development which leaves the natural environment in a measurably better stated than beforehand.

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Case Studies

Planning for Biodiversity - Advice Note for development in South Downs National Park

In 2012 we worked on behalf of the South Downs National Park Authority, and in association with Alison Farmer Associates landscape practice, to prepare a householder Advice Note on considering the possible ecological, landscape and cultural heritage impacts of proposed developments, alterations or extensions.

The project required a consideration of the special ecological characteristics of the ......

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The Government’s ‘25 Year Environment Plan’ (HMG, 2018) set out a policy ambition to consult on mandatory BNG for development and to embed environmental net gain principle into the planning system. A Defra consultation on mandatory BNG, advocating a minimum of 10% BNG for all development, took place in December 2018[1] with the responses published in July 2019[2].  The Draft Environment Bill proposes to mandate a minimum of 10% BNG for all development. Timescales for the enactment of the Bill are currently unknown.

In 2019 Defra published the Biodiversity Metric 2.0 (‘the Metric’) (Crosher et al., 2019). The metric provides a means of evaluating biodiversity losses and gains through development in a robust and consistent manner. The metric enforces the mitigation hierarchy whereby impacts to biodiversity should first be avoided, then minimised and mitigated, before being compensated where losses cannot be avoided. The Metric calculates the biodiversity value of a site before and after development to establish the change in biodiversity attributable to a particular development project.

Defra and Natural England are expecting to consult on a further revision to the Metric – Metric 3.0 – in spring 2021.

We have already accrued extensive experience in Biodiversity Net Gain Assessment having run a series of breakfast seminars on BNG in early 2020, and since then have delivered a number of online CPD events  for forward-thinking developers.  We have already completed BNG assessments for over a dozen development projects on behalf of our clients.

Let us know if we can help you too.


[1] Defra (2018): Net Gain – Consultation proposals. Available online:

[2] Defra (2019): Net Gain – Summary of responses and government response. Available online:

Ecological Surveys

Impact Assessments

Environmental Planning


Biodiversity Net Gain