A Biodiversity Metric for Scotland’s Planning System

Latest metric updates

September 2024:

  • Our consultation on the key issues to be addressed when developing a Scottish biodiversity metric closed on the 10th May 2024.  A summary of the key issues identified through the consultation is now available.
  • A roundtable discussion on the development of a Scottish biodiversity metric was held on 01 May 2024. An overview of the comments and topics discussed can be read in the meeting summary note.

Contents

  1. Introduction
    1. Background
  2. Developing a Scottish biodiversity metric 
    1. Initial consultations and identification of key issues
    2. Next steps: Establish metric foundations and address priority issues
  3. Useful links to further information
    1. Biodiversity enhancement in Scotland
    2. England’s statutory biodiversity metric and associated information

Introduction

This webpage outlines the work that NatureScot is undertaking to develop a biodiversity metric for Scotland’s planning system, to support delivery of National Planning Framework 4 (NPF4) Policy 3b. This work has been commissioned by the Scottish Government.

NPF4 Policy 3b states that national and major developments, or those subject to Environmental Impact Assessment (EIA), will only be supported where it can be shown that they will conserve, restore and enhance biodiversity, including nature networks, so they are in a demonstrably better state than without intervention. The policy requires that such proposals demonstrate significant biodiversity enhancement, in addition to any proposed mitigation.

The commission’s final outputs will include a Scottish biodiversity metric tool for use in the planning system and accompanying guidance (together with any additional supporting information). 

Discrete, focussed outputs will also be published as the project progresses, these will provide early indication of the proposed metric foundations and intended approach in advance of the metric tool being released for use. This early signalling will enable stakeholders to begin preparations for adopting the new Scottish biodiversity metric.

While a Scottish biodiversity metric is being developed, the Scottish Government’s Draft Planning Guidance on Biodiversity (November 2023) advises that “…the absence of a universally adopted Scottish methodology/tool should not be used to frustrate or delay decision making, and a flexible approach will be required”. 

For guidance on securing positive effects for biodiversity from local development to support NPF4 Policy 3c, please refer to our Developing with Nature Guidance. 

This webpage will be updated periodically as this project progresses. If you have any queries, or further comments that could assist with the development of a Scottish biodiversity metric, please email: [email protected].

Background

NPF4 Policy 3b does not specify or require a particular assessment approach or methodology to demonstrate the delivery of positive effects for biodiversity, though the policy makes it clear that best practice assessment methods should be used. In the absence of an established Scottish approach, a range of methods, including variations of England’s statutory biodiversity metric (see Annex A for further information), are being used to measure biodiversity on development sites in Scotland. It is acknowledged that this lack of a standardised approach could lead to inconsistencies, which could undermine delivery of NPF4 objectives. 

To address this, Scottish Government commissioned research into ‘Approaches to Measuring Biodiversity in Scotland,’ a report on which was published in September 2023. This report considered methodologies for measuring biodiversity at site-level and included an in-depth review of the English statutory biodiversity metric (often referred to as the ‘DEFRA metric’ or the ‘English metric’), concluding that with refinement England’s metric could be adapted for use in the Scottish planning system. Scottish Government welcomed the findings and in December 2023 commissioned NatureScot to develop an adapted metric suitable for use in supporting delivery of NPF4 Policy 3b.

It is recognised that the use and application of a Scottish biodiversity metric will be different to the use of the English metric. This reflects that Scotland’s policy-led approach to delivering biodiversity enhancement differs from England’s legislative/statutory approach. A Scottish biodiversity metric must be suitable for use within the Scottish planning and consenting context as a tool to inform professional judgement by the decision maker. 

Developing a Scottish biodiversity metric 

The commission is to develop a metric specifically to support delivery of NPF4 Policy 3b, with a focus on adapting the existing English metric to produce a tool that is suitable for use within Scotland’s policy and environmental context. 

As this project progresses, updates on the intended approach will be added below. Early signalling of the proposed metric foundations will also be communicated here, to enable preparations for adopting the new Scottish biodiversity metric to begin.

Initial consultations and identification of key issues

During this initial consultation phase of the Scottish biodiversity metric project, key stakeholder groups and contacts were identified. To inform our work and the approach taken, initial views were then sought on the key issues to be addressed when developing a Scottish metric, via a public consultation and a key stakeholder roundtable discussion. 

NatureScot consulted on its paper, ‘A Biodiversity Metric for Scotland's Planning System - Key Issues’, in spring 2024. The consultation was open for comments from 4th April to 10th May 2024, with responses from all interested parties welcomed. Key themes and headline messages that were identified through the consultation have been summarised in a short paper: Scottish biodiversity metric - Key issues consultation - Initial overview of responses.

A roundtable discussion on the development of a Scottish biodiversity metric for the planning system was held on 1st May 2024.  A summary of the comments and topics discussed during the roundtable is available in the meeting summary note.

A wide range of views on a Scottish biodiversity metric were shared through the key issues consultation and roundtable discussion. Although these broadly supported the key issues previously identified and the proposed project approach, a number of additional matters were raised by stakeholders. All feedback provided through these initial consultations will be considered and used to inform the development of the metric. 

This phase of the metric work was completed in early September 2024.

Next steps: Establish metric foundations and address priority issues

Work will now progress to addressing some of the priority issues that have been identified and shaping the basic structure of the Scottish biodiversity metric. This will require a review of the components that underpin how the metric works, including the metric rules and principles, and which habitat classification system(s) will be used (plus any required translations between classifications). 

As work progresses, we will be seeking more focussed discussions with key stakeholders, particularly with those who have experience of applying a metric approach in Scotland and those who have expressed an interest in contributing their expertise to the metric development. We will also explore opportunities for live testing with stakeholders. Further opportunities to contribute will include through established fora and open consultations published on the NatureScot website.

Biodiversity enhancement in Scotland

England’s statutory biodiversity metric and associated information

An overview of England’s statutory biodiversity metric is provided in Annex A, but see also the following useful links:

Annex A: Overview of England’s statutory biodiversity metric

This annex provides an overview of England’s statutory biodiversity metric, the adaption of which provides the starting point for developing a Scottish biodiversity metric for planning. It does not provide detailed information on its methodology and application.  This, and guidance on its use, can be found on the Department for Environment, Food & Rural Affairs pages of the UK Government website.  

Under England’s planning system, most development (unless exempted) can not be granted planning permission unless it can show that it will provide at least a 10% uplift in the biodiversity value of the site (i.e. delivering ‘biodiversity net gain’). Biodiversity value is measured in standardised ‘biodiversity units’, which are required to be calculated using the statutory biodiversity metric tool. This is an Excel spreadsheet created tool, that provides a standardised approach to quantifying the level of biodiversity on a development site pre-intervention, and what is intended to exist following development (post-intervention). The tool is founded on habitats as a proxy for measuring biodiversity (rather than an alternative such as species or ecosystem health), and the application of a set of pre-determined multipliers. These multipliers have been established based on current scientific understanding and expert opinion of habitats under ‘average’ environmental conditions in England.

Diagram illustrating the various components of England's statutory biodiversity metric, and their use in calculating biodiversity net gain.
Figure 1: Overview of the component parts of England’s statutory biodiversity metric, indicating the range of categories with their multipliers that are applied in calculating biodiversity units.

For the site in question, the metric seperately calculates the biodiversity value (in biodiversity units) of what currently exists pre-intervention, and what will remain or is planned to be established post-intervention.  It does this by multiplying the area or linear extent of each different habitat identified on the site, by pre-determined multipliers for each of the metric’s component parts – Distinctiveness, Condition, Strategic Significance and three Risk Factors. The biodiveristy units calculated for the three different forms of habitat - area of habitat (ha), length of hedgerow (km) and length of watercourses (km) - are processed separately, and can not be summed, traded or converted between them.

For calculating biodiversity units for the baseline, a site’s habitats are identified and their condition is assessed.  The habitat type identified determines the level of distinctiveness, and informs the level of strategic significance, to be applied. The extent of each habitat is then multiplied by the appropriate pre-determined multipliers (for distinctiveness, condition and strategic significance), to calculate the number of pre-intervention biodiversity units of the site. 

This is repeated for the habitats that will exist post-intervention, but with an additional set of predetermined ‘risk factors’ applied to account for the uncertainty, time-lag and any separation between existing and future biodiversity. Each habitat type has pre-determined levels of difficulty assigned in either creating or enhancing them, and the average time required to reach a defined condition. The spatial risk factor is determined by where in relation to the development site the habitat is being delivered, penalising off-site in favour of on-site provision. Each of these risk multipliers are applied to the habitats that will be enhanced or created post-intervention (existing habitats that remain unchanged are not exposed to risk).

The difference in biodiversity units between the pre-intervention score and post-intervention score indicates whether biodiversity net gain will be delivered, and the scale of uplift that will be achieved.

To apply the metric tool, a competent person is required to identify and classify the extent of different habitats within the site and assess their current condition (based on ecological survey), and establish their strategic significance (based on a review of the Local Nature Recovery Strategy or alternative strategy). This establishes the pre-intervention score. They also need to establish what habitats will remain, be enhanced or created and the condition it is intended to achieve post-intervention, and the strategic significance of these habitats. Inputting this information in to the metric tool automatically assigns the pre-determined multipliers for each habitat in calculating the appropriate number of biodiversity units.

It is recognised that the metric has limitiations. While it is underpinned by ecological evidence and expert opinion, it is still applying a relatively simply and broad-brush approach to calculating change in biodiversity. Habitat as a proxy for biodiversity does not consider landscape structure, and the intricacies, complexities and functioning of ecosystems that biodiversity depends upon. Nonetheless the metric provides a useful tool for informing decisions on delivering the policy’s requirements when appropriately applied.