Measuring biodiversity: research into approaches

Executive Summary

Aims and objectives

This project aimed to review and recommend methodologies for the measurement of biodiversity at the site level in Scotland. In doing so the research considered end-user needs across four key policy areas: agriculture, conservation and biodiversity monitoring, natural capital markets and planning and development. A combination of stakeholder analysis and review of existing tools and metrics was used to develop the recommendations presented in this report.

The main objectives include:

1. To engage stakeholders within four key policy areas to identify and prioritise relevant criteria for assessing existing metrics or tools.

2. To assess a range of biodiversity metrics and tools that could be used to measure biodiversity at the site level and determine which aspects of current approaches meet the needs of end-users in Scotland.

3. To review Natural England's Biodiversity Metric 3.1 to assess its applicability for use in Scotland and in policy areas extending beyond planning and development, and identify any adaptations needed to make Natural England's Metric 3.1 fit for use in Scotland.

4. To engage stakeholders to sense check key findings, identify concerns, and ensure that the recommendations align with stakeholder needs.

5. Drawing on the above, advise on preferred approach and scope of guidance that will be required.

Approach

To address the objectives outlined above, the research was undertaken in several steps:

• A list of assessment critera for evaluating biodiversity metrics was developed and prioritised through two stakeholder workshops. Workshops included representatives from four key policy areas: agriculture, conservation and biodiversity monitoring, natural capital markets, and planning and develoipment.
• Twenty six existing biodiversity tools and metrics were identified and compared using the list of assessment criteria described above. Consideration was given as to whether these tools and metrics could, in whole or in part, be applicable in a Scottish biodiversity metric.
• An in-depth review was completed for Natural England's Biodiversity Metric 3.1, including review of guidance and techical references, land-use change scenario testing, stakeholder discussions, and an evaluation of the data needs underpinning the metric. Through this review we assessed whether this metric could, in whole or in part, be adapted for Scotland and applied across the four policy areas.
• A final sense-checking workshop was held with stakeholders to review and provide input on the findings and to gain further insights.

Summary of main findings

The results of this report demonstrate both consensus and divergencies in priorities across the four policy areas. To meet the needs of all four sectors, a biodiversity measurement approach or metric will need both common features and some degree of flexibility in its application. A framework, or standard, is needed that can integrate multiple metrics or tools to monitor biodiversity and provide consistent results, while allowing flexibility to tailor metrics and tools depending on different user or policy needs (Figure ES1). This framework could incorporate both new elements and elements from existing tools that are adapted for use in Scotland.

As the four policy areas differ in their needs for measurements of biodiversity, this also means differing requirements for time and effort, level of detail, training and expertise, and regularity of assessment. For example, farm biodiversity audits may only need meaningful, targeted participatory monitoring which is achievable with basic training and resources. This monitoring could rely on a qualitative habitat condition assessment, with more complex (but comparable) approaches scaled for other uses. In contrast, high integrity ecosystem markets such as biodiversity credits require more robust quantification of a broader selection of indicators to fully capture biodiversity. Needs for the planning and development sector may fall somewhere between these policy areas depending on the scale or impact of development being considered. The biodiversity monitoring sector has a need to inform and record indicator data across a range of applications spanning the three other policy sectors. Thus, for any site, the degree of complexity needs to reflect the purpose, the user and the priority outcomes for the habitat, species or ecosystem.

Figure ES1 Conceptual biodiversity metric framework illustrating increasing complexity of assessment from left to right across the range of biodiversity indicators (top) and policy sectors (bottom).

Results from the metric reviews and workshops illustrate that a biodiversity approach for Scotland needs to address a number of elements outlined below:

Habitat and species metrics:

• Including habitat indicators in a biodiversity metric was identified as a high priority across all policy areas. Assessments of habitat condition should be scaled to meet the needs of different end-users and ecological objectives. Irreplaceable habitats should be identified and assessed accordingly within the metric. Habitat classification systems should be flexible to meet the needs, skills, and training of end-users, with appropriate correspondence tables developed to allow translation between classifications (e.g. UK Hab to EUNIS). Natural England's Biodiversity Metric 3.1 could be adapted to meet this need.
• Including species indicators was identified as moderate or high priority across all policy areas.This should be scalable in terms of scope and effort to meet the needs of different end users and objectives. Species based metrics should reflect the presence of one or more indicator species and the diversity of species or taxa. The choice of species should reflect the context in which a metric is being used. Further research is recommended to identify indicator species and appropriate species-based metrics for Scotland.

Connectivity metrics:

Including connectivity indicators was identified as a high priority across all policy sectors. Further research is recommended to determine appropriate connectivity measures across different habitat and land use contexts and scales. There are multiple ways connectivity can be assessed (e.g., abundance of similar habitats, permeabiity and dispersal) and existing efforts to identify opportunity areas for habitat creation in Scotland that can be built upon.

Ecosystem function, health and integrity metrics:

Including measures of ecosystem health was also identified as high priority, particularly as part of more detailed or robust assessments for monitoring, larger project planning and ecosystem markets. It could also be incorporated into wider system and soil health assessments in the agricultural sector. We recommend that suitable ecosystem health indicators be identified for different habitats and land uses reflecting condition, function, and resilience. Review of Scotland's Environment ecosystem health indicators^[1] which reflect a range of nationally available data and reporting at national scale could be a starting point to address indicators for these elements.

Monitoring:

Ongoing or long-term monitoring is important to assess changes in biodiversity, and provides a means of identifying problems and potential interventions to enhance biodiversity outcomes. Chosen metrics or indicators should be amenable to ongoing monitoring or repeated estimation and reflect current and future pressures. This means they should be sensitive to and able to reflect changing impacts. Scoring systems for future biodiversity should also be sensitive to changing pressures (e.g. climate change, disease and pest risks).

Scientific robustness and transparency:

• Results from the metric reviews and workshops highlight the need for the approach to be accessible, understandable, and flexible in how it is applied across different uses or spatial scales. The approach should avoid oversimplification, allowing for robust assessment by experienced and trained staff, but also meaningful where participatory or citizen science approaches are used. Thus, indicators and protocols should allow for repeatable and comparable results, whilst requiring varying levels of effort and expertise for data collection depending on their use. Guidance and training should be appropriate for the range of users and applications.
• The methodology and indicator data used to calculate the metric (and estimate biodiversity units) should be accessible and published to aid transparency and understanding.
• Results from the metric reviews and workshops also illustrate that Scottish biodiversity metrics need to be clear, concise and transparent and scientifically robust in terms of measurability. Chosen metrics or indicators should have a robust scientific basis and provide meaningful measures of biodiversity and/or ecosystem health. They should ensure a standardised framework that allows interrogation to reduce the risk of green-washing or gaming.

Wider ecosystem services:

Stakeholders noted the desirability to include wider ecosystem service benefits within a biodiversity metric framework. This has been captured to some extent by Natural England's Environmental Benefits of Nature (EBN) tool, which is designed to work alongside the Biodiversity Metric 3.1 and provides a qualitative assessment of the impact of net gain actions across a range of 18 ecosystem services, evaluated at 1, 10 and 30 years from implementation. Review of the EBN was outside the scope of this study, but it may be adjusted to reflect Scottish circumstances and applications.

Applicability of Natural England's Biodiversity Metric 3.1 in Scotland:

The Biodiversity Metric 3.1 was designed for calculating biodiversity net gain within the planning and development sector. As such it is not fully applicable to other sectors. However, with refinement it could be adapted for planning and development use, and as part of a wider set of metrics within a biodiversity framework.

To adapt Biodiversity Metric 3.1 for use in Scotland, experts would need to engage to ensure elements are fit for use in Scotland, including updating the User Guide/Technical Annexes, updating the list of irreplaceable and Annex 1 habitats to reflect Scottish circumstances, ensuring peatlands are correctly accounted for, reviewing trading rules, considering how UK Hab relates to other classification systems that may be used within a broader framework, and determining the appropriateness of condition criteria for habitats in Scotland. Spatial datasets would need to be assessed to determine where spatial data are lacking, and whether existing local strategies and plans are suitable to inform strategic significance. Environmental conditions vary widely across Scotland, influencing the risks associated with habitat creation. Average risk multipliers, as used in Metric 3.1, are thus not appropriate for Scotland and greater flexibility is needed in assigning risk multipliers. It is also important to ensure multipliers interact appropriately to incentivise the creation of good quality habitats. With ecological connectivity considered a priority across policy sectors, Metric 3.1 should be adapted to include connectivity measures, as well as the other priority indicators identified above (condition, species, ecosystem health, and wider ecosystem benefits).

Consideration should be given to training availability and Scotland's capacity to deliver both from a regulatory perspective and also for on the ground surveys. This would require an assessment of potential skills gaps and where there is a need for training and clear guidelines.

Consideration is also needed for how this type of metric would fit within a broader framework. For example, a standardised approach to condition assessment criteria could align policy sectors, yet still meet the needs of different sectors and uses. Additionally, incorporating management/systems aspects would meet the needs of the agricultural sector. Agriculture takes a systems-approach to land management and consequently aspects relating to management, rotation and spatial/temporal dynamics are important to include to meet the end needs of this sector.

Conclusions and recommendations

To meet the needs of all four policy sectors, a framework, or standard, is needed that integrates multiple metrics or tools to monitor biodiversity. This biodiversity framework should ensure consistency across all policy sectors while maintaining flexiblity around which protocols and indicators to select. The framework should be organised so that relevant existing metrics, protocols or tools can be integrated and used to assess biodiversity. To do this, the framework needs to set expectations around when to select different indicators and protocols, how to integrate existing methods, and how to ensure that results are reasonably consistent across approaches (e.g., different condition assessments need to align or conform to a common expectation of low, moderate and good condition). The framework will also need to outline how the outputs of different metrics or methods relate, particularly for trading or monitoring biodiversity across sectors.

The existing biodiversity metrics reviewed in this report use a variety of ways to measure biodiversity that are not always comparable or adequately capture the full range of biodiversity functions in terms of habitats, species and ecosystem health. Further, many metrics reviewed use proxy, or modeled, measures of biodiversity that are too coarse to be appled at a site scale. An approach for Scotland may benefit from incorporating certain elements from existing metrics, but additional work is needed to fully address the list of priority criteria identified by stakeholders, including habitat condition, species indicators, ecosystem health, ecological connectivity and wider ecosystem benefits. With refinement, Natural England's Biodiversity Metric 3.1 could be adapted as part of a wider set of metrics within a biodiversity framework.