Aylesbury Vale Area

Biodiversity Accounting Supplementary Planning Document

Ended on the 19th March 2021
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5.0 Biodiversity Accounting – The Process

5.1 The term Biodiversity Accounting in this supplementary planning document relates to the UK Biodiversity Net Gain metric approach, which was previously known as Biodiversity Offsetting. To achieve a Biodiversity Net Gain, a development must have a higher biodiversity value post-development compared with the pre-development, baseline value.

5.2 The council expects applications to deliver, as a minimum, the net gain requirement set out in the government's forthcoming Environment Act, to assist in meeting Buckinghamshire's biodiversity objectives, see for example the Biodiversity Action Plan.

5.3 Biodiversity will be measured using Defra's metric or the council's locally-agreed variant, Warwickshire County Council's Biodiversity Impact Assessment Calculator Warwickshire County Council Biodiversity Impact Assessment Calculator . If an alternative metric is used the council may require a review fee.

5.4 The Biodiversity Accounting Tool can be used once evidence has been gathered to gain information on site conditions. The evidence may include: a Construction and Environmental Management Plan; a Landscape and Ecological Management Plan; plus, any necessary legal agreements (planning obligations), and their subsequent discharge.

5.5 The Biodiversity Accounting Tool is a decision-aiding tool that can be used in an iterative design process to continually inform successive development layouts and choices of materials, to improve biodiversity in development. This is illustrated in Exemplification 3 below.

Exemplification 3: Avoidance and on-site mitigation

5.6 Increasing the use of avoidance and minimising impacts in project design through iterative application of the mitigation hierarchy using the Biodiversity Accounting Tool to inform successive designs that improve biodiversity gain.

biodiversity accounting tool

Source:Adapted from the Mitigation Hierarchy Guide

5.7 Exemplification 4 below, outlines the biodiversity accounting process for planning applications.

Exemplification 4: Biodiversity Accounting Process for Planning Application Determination and Implementation

  1. Submitting a Planning Application for Validation by the Council.

    When required, a Biodiversity Impact Assessment, using the Biodiversity Accounting Tool, will be expected to be submitted with all qualifying applications, in addition to the usual ecological report and surveys. Some applications will not be validated unless a Biodiversity Impact Assessment has been submitted.

  2. Determination of a Planning Application.

    Applications will be assessed following the National Planning Policy Framework's Avoid, Mitigate and Compensatoryhierarchy. Where opportunities to avoid biodiversity losses, mitigate their losses or on-site compensatory measures are maximised, the application will either result in a biodiversity net gain, a loss or a neutral effect. Where there is a net gain in biodiversity, planning obligations to secure the net gain on-site, will be added to the planning permission.

  3. If there is a net loss of biodiversity on the development site and this cannot be changed through a redesign of the development, two options are available to the developer. The net gain requirement can be offset from the development site either through
    1. a receptor site that the developer finds and has a planning obligation to ensure that the net gain on that site will be there in perpetuity or
    2. provide a financial contribution to the council for the council to place the net gain in a receptor site of the council's choosing. The biodiversity receptor sitewill be created, monitored and managed over the lifetime of the impacts of the development – to compensate for the biodiversity value of habitats lost by the development, plus the required gain of at least 10%. This 10% is a proxy figure for what is expected to be required by the Environment Act 2021. This Supplementary Planning Document does not set a figure but defers to the Environment Bill and its resulting enactment.


5.8 Exemplification 5 below, sets out the four stages of the Biodiversity Accounting Process.

Exemplification 5: The Four Stages of the Biodiversity Accounting Process

A simple way to describe the biodiversity accounting process is to consider it in stages:

Stage 1: Assess the development site by carrying out an ecological survey (habitats and species)

Stage 2: Avoid, mitigate and compensate on site.

Stage 3: Calculate the biodiversity pre-development baseline by using the metric tool.

Stage 4: Calculate a post-development biodiversity baseline. If there is at least a 10% gain on site then that is good, if there is a loss – revise the design until there is a gain. If this cannot be achieved on-site, make compensatory arrangements by having the net gain off site.

The Biodiversity Accounting Tool helps to calculate the net gain or loss.


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