Measuring biodiversity: research into approaches
This report considers methodologies for measuring biodiversity at site-level for use in Scotland.
Results: Metrics review
Biodiversity Metric 3.1 and an adjusted version of that tool used by Scottish and Southern Electricity Networks (SSEN) were the only tools in the review designed specifically for application to biodiversity offsetting /BNG in a development context. Two further tools or approaches were developed specifically to inform natural capital markets for biodiversity credits. And one tool, the Norwegian Nature Index, was designed for monitoring and reporting trends in biodiversity and ecosystem health. The full list of tools and metrics included in this review, together with links to documentation is reproduced in Annex 4.
Habitats and Species
The assessment of metrics against the criteria for Habitat and Species (i.e. what a metric measures) is summarised in Table 3. The darker shades indicate the degree to which each criteria is met, this may be fully, partially or not included. For example, with 'habitat extent', full consideration would include extent, condition and significance/distinctiveness. The full assessment with notes is included in an accompanying Excel file.
Most business focused tools use a partial species-based metric such as Mean Species Abundance (i.e. an indicator of local biodiversity intactness based on the undisturbed state - MSA) or Potentially Disappeared Fraction (i.e. the fraction of species richness that is lost due to environmental impact - PDF). These metrics do not directly measure species presence or abundance. Instead, land use type and intensity are used as a proxy measure, with relationships between land use and species drawn from existing literature or modelling. Typically, the land use is then compared to species abundance in the natural and undisturbed habitat expected in a given location. MSA or PDF relates to the change in the extent and condition of habitat/s affected by the activity being assessed. MSA can be further adjusted to account for the drivers such as climate change or nutrient inputs, the impacts of which will vary across different habitat types.
The main criticisms of approaches such as MSA is that it is not comparable across different ecosystem or habitat types (i.e. it is a measure of relative not absolute species abundance) and it is derived from very high level global assessment based on broad ecosystem types. As such it may not be sensitive to variations and local contexts in site-level habitat assessments.
Biodiversity Metric 3.1 does not directly consider species presence or abundance. It instead uses a proxy measure of biodiversity based on habitat extent, condition and distinctiveness. However, presence of positive or negative indicator species are included within condition assessments of some habitats.
| Name |
HE |
HC |
HPI |
EH & F |
EFD |
Species |
OM |
P |
|---|---|---|---|---|---|---|---|---|
| Agrobiodiversity Index |
N |
N |
N |
N |
F |
N |
N |
N |
| Biodiversity Credits (Wallacea Trust) |
F |
F |
F |
F |
F |
F |
F |
P |
| Biodiversity Footprint for Financial Institutions (BFFI) |
N |
N |
N |
P |
N |
P |
N |
F |
| Biodiversity Footprint Methodology (BFM) |
P |
N |
N |
P |
N |
P |
N |
F |
| Biodiversity Impact Metric (BIM) |
F |
N |
F |
P |
N |
P |
N |
P |
| Biodiversity Intactness Index |
N |
N |
N |
P |
P |
F |
N |
P |
| Biodiversity Indicator and Reporting System (BIRS) Holcim |
F |
N |
F |
P |
N |
P |
F |
N |
| Biodiversity Indicators for Site-based Impacts (BISI) |
P |
P |
P |
P |
N |
P |
N |
F |
| Biodiversity Metric 3.1 |
F |
P |
F |
N |
N |
P |
N |
N |
| Biodiversity Monitoring System (BMS) |
N |
F |
P |
N |
N |
P |
F |
F |
| Biodiversity Net Gain Calculator (BNGC) |
P |
N |
N |
P |
N |
P |
N |
P |
| Biodiversity Performance Tool (BPT) |
F |
F |
N |
P |
P |
P |
F |
F |
| BioScope |
N |
N |
N |
P |
N |
P |
N |
F |
| Corporate Biodiversity Footprint (CBF) |
P |
N |
N |
P |
N |
P |
N |
F |
| Exploring Natural Capital Opportunities, Risks and Exposure (ENCORE) |
N |
N |
N |
P |
N |
P |
N |
F |
| Global Biodiversity Score® (GBS®) |
P |
N |
N |
N |
N |
P |
N |
F |
| Global Impact Database (GID) |
P |
N |
N |
P |
N |
P |
N |
F |
| Integrated Biodiversity Assessment Tool (IBAT) |
N |
N |
F |
P |
N |
P |
F |
F |
| LIFE Methodology (LIFE) |
P |
N |
P |
P |
N |
P |
N |
N |
| Natural Asset Recovery Investment Analytics (NARIA) |
P |
F |
N |
F |
F |
F |
N |
N |
| Norwegian Nature Index |
N |
N |
N |
P |
P |
F |
F |
P |
| Product Biodiversity Footprint (PBF) |
N |
N |
N |
P |
N |
P |
N |
F |
| ReCiPe |
N |
N |
N |
P |
N |
P |
N |
F |
| Species Threat Abatement and Restoration metric (STAR) |
N |
N |
N |
N |
N |
P |
N |
F |
| SSE Biodiversity Project Toolkit |
F |
P |
F |
N |
N |
P |
N |
N |
| The Biodiversity Integrated Assessment and Computation Tool (BINTACT) |
P |
N |
N |
P |
N |
P |
N |
F |
F=Full
P=Partial
N=None
No information
HE = Habitat Extent
HC = Habitat Connectivity
HPI = Habitat: Priority or Irreplaceable
EH & F = Ecosystem Health and Function
EFD = Ecosystem Functional Diversity
OM = Ongoing Monitoring
P = Current and future pressures (e.g. climate change risks)
Approaches used for biodiversity credit markets, CreditNature's Natural Asset Recovery Investment Analytics (NARIA) and the Wallacea Trust's Biodiversity Credits methodology use multiple metrics to capture different aspects of biodiversity including habitats, species, connectivity and ecosystem function. The aim is to provide a more robust measure of ecosystem integrity. The Wallacea Trust recommends at least five metrics that can be tailored to suit the context of the habitat or site being assessed. Examples of potential metrics for two different ecosystems are illustrated in Table 4. In addition, the Wallacea Trust approach requires that the metrics must reflect the conservation objectives of the site, contain at least one habitat or floral composition metric for terrestrial sites, cover all ecosystem services likely to be affected, and not include carbon sequestration. The NARIA method uses different measures to produce an overall ecosystem integrity index (Figure 3).
The Norwegian Environment Agency's Norwegian Nature Index is a composite approach using monitoring data, expert evaluations and modelling of 260 species indicators over seven ecosystems. This approach is currently being adapted for use in the Cairngorms National Park and forms the basis of a biodiversity measurement tool being developed by Forest Research for Forestry and Land Scotland.
Table 4: Example metrics for different ecosystems in the Wallacea Trust approach (source: Wallacea Trust)
Lowland arable and livestock farmland converting to rewilding or regenerative farming
1. Natural England's biodiversity metric 3.0 to measure uplift in habitats
2. Biomass of arthropods to measure changes in total food availability for insectivorous birds
3. Species richness and abundance of pollinator bees and hoverflies
4. Changes in butterfly and macro-moth species richness and abundance
5. Changes in UK Red, Amber or Local Biodiversity Action Plan breeding birds
6. Changes in bat species richness and abundance
Coral Reefs
1. Reef rugosity measured by 3D mapping
2. Coral cover
3. Fish species richness and abundance measured from stereo video fish counting
4. Total macro-invertebrate species richness measured from eDNA sampling
5. Abundance of commercially exploited invertebrate species on the reef
Habitat connectivity was an important criterion raised during our stakeholder engagement. Very few of the reviewed metrics directly incorporate this. NARIA directly includes a model of landscape connectivity incorporating barriers and landscape permeability. The agriculture sector tools Biodiversity Monitoring System (BMS) and Biodiversity Performance Tool (BPT) consider connectivity on farms through the presence of linear corridors and distance between semi-natural habitats respectively. Other metrics are partial, for example considering impacts or mitigations in the contexts of their surrounding area, but not directly measuring connectivity.
Few metrics considered the presence of irreplaceable or high value habitats and, when included, this was achieved through scoring the importance or rarity of habitats either at the regional or global level. Ecosystem health and function is only partially considered by most metrics. For example, it may be implicit in the range indicators used, the impact on ecosystem services, or the pressures used to calculate metrics such as MSA. Only NARIA and the suite of indicators required by Wallacea are intended to directly capture ecosystem health. Functional diversity was rarely captured directly although it may be implied from the variety of indicators used, or captured by specific elements of the metric (NARIA) or the variety of metrics used (Wallacea).
Metrics typically did not incorporate ongoing monitoring. The Norwegian Nature Index is directly linked to species monitoring and is intended to produce regular updates. The Biodiversity Indictor and Reporting System (BIRS) requires annual habitat extent with condition assessed every 3 to 5 years. The BMS also required updates every 3 to 5 years. The Integrated Biodiversity Assessment Tool (IBAT) re-evaluates Key Biodiversity Areas every 8 to 12 years. NARIA uses ongoing monitoring to determine biodiversity uplift to confirm biodiversity credits.
As noted above, metrics such as MSA and PDF can include the impact of pressures such as climate change on biodiversity. However, this is not mandated in those metrics and different types of pressure may or may not be used depending on user needs. In addition to climate change, typical pressures that may affect ecosystem health include land use and use intensity, human population, pollution including nutrients, habitat fragmentation and encroachment, pathogens and pests, and alien or invasive species.
Effort and ease of use
Most of the metrics are open access, using publicly available data and methods (Table 5). Some have an open access methodology, but charge for access to data (IBAT and STAR). Others such as NARIA use proprietary models. However, open access metrics may still require expertise in understanding the data or undertaking the biodiversity impact calculations. For tools such as Biodiversity Metric 3.1, use of the spreadsheet user-interface may not require specific expertise, but ecological expertise is required in the collection of underlying data (e.g. habitat condition assessment).
| Name |
Open access |
Scalable: financial |
Scalable: spatial |
Expertise |
Time to use |
Cost of use |
|---|---|---|---|---|---|---|
| Agrobiodiversity Index |
F |
F |
F |
P |
||
| Biodiversity Credits (Wallacea) |
P |
F |
F |
P |
||
| Biodiversity Footprint for Financial Institutions (BFFI) |
F |
F |
F |
P |
||
| Biodiversity Footprint Methodology (BFM) |
F |
F |
F |
P |
||
| Biodiversity Impact Metric (BIM) |
F |
F |
F |
P |
||
| Biodiversity Intactness Index |
F |
F |
N |
P |
||
| Biodiversity Indicator and Reporting System (BIRS) Holcim |
F |
F |
F |
P |
F |
F |
| Biodiversity Indicators for Site-based Impacts (BISI) |
F |
F |
F |
P |
||
| Biodiversity Metric 3.1 |
F |
F |
F |
N |
||
| Biodiversity Monitoring System (BMS) |
N |
F |
||||
| Biodiversity Net Gain Calculator (BNGC) |
N |
F |
F |
P |
||
| Biodiversity Performance Tool (BPT) |
N |
N |
P |
P |
||
| BioScope |
F |
F |
F |
P |
||
| Corporate Biodiversity Footprint (CBF) |
F |
F |
F |
P |
||
| Exploring Natural Capital Opportunities, Risks and Exposure (ENCORE) |
F |
F |
F |
P |
||
| Global Biodiversity Score® (GBS®) |
F |
F |
F |
P |
||
| Global Impact Database (GID) |
F |
F |
F |
P |
||
| Integrated Biodiversity Assessment Tool (IBAT) |
P |
P |
F |
P |
N |
|
| LIFE Methodology (LIFE) |
F |
F |
F |
P |
||
| Natural Asset Recovery Investment Analytics (NARIA) |
N |
F |
F |
|||
| Norwegian Nature Index |
F |
F |
F |
P |
||
| Product Biodiversity Footprint (PBF) |
F |
F |
F |
P |
||
| ReCiPe |
F |
F |
F |
P |
||
| Species Threat Abatement and Restoration metric (STAR) |
P |
P |
F |
P |
N |
|
| SSE Biodiversity Project Toolkit |
F |
F |
F |
N |
||
| The Biodiversity Integrated Assessment and Computation Tool (BINTACT) |
F |
F |
F |
P |
F - Full
P - Partial
N - None
No information
Most of the metrics were able to be spatially scaled without entailing disproportionate costs. The IBAT and STAR tools are partially scalable in financial terms as assessments over larger or more numerous sites entail larger data purchase fees. Although costs do not rise proportionally with the extent of spatial data available, there is the potential for large cost increases at the thresholds for extent. The BMS and BPT metrics are designed to be used at farm level, consequently there was no information on scaling costs, and spatial scalability was limited as the indicators used in these tools may be location specific.
Very few of the metrics provided information on the time requirements (e.g., number of hours/days for data collection and analysis) or costs of use. BPT provides an estimate of per farm assessment costs. BIRS recognises the time and cost implication of adopting the approach, noting that a higher investment will provide more meaningful results. But overall the BIRS approach is intended to minimise costs. The IBAT and STAR website provide information on subscription costs for access to their datasets.
Useability and comparability
Most of the metrics were scored as 'partial' for being clear, concise and transparent (Table 6). The reason for this scoring, was that although the methodology may be established and well documented, it is nevertheless difficult to determine the relative impacts of different indicators on an overall composite biodiversity score. More transparent metrics such as the Norwegian Nature Index, although having complex underlying calculations, also offer users the opportunity to investigate individual indicators.
The scientific robustness of the metrics was considered high for all of the metrics, reflecting a basis in underlying literature or good descriptions of the methodology that can be scrutinised. However, there may be variations in terms of what biodiversity criteria (see Table 3) are considered and whether the approach is suited to a particular application.
Few of the metrics provided information on their alignment with current or future policy objectives. This may be implicit in the motivation for using a metric, or some of the indicators used. The test for this assessment was whether policy objectives were explicitly mentioned in the accompanying literature. Alignment with current or future monitoring relates to whether the metric uses data from monitoring. The distinction we make with 'ongoing monitoring' under biodiversity measurement, is not whether the metric requires monitoring but whether the underlying data results from monitoring. Most metrics do not, instead relying on data from one-off assessments.
Most metrics are not intended to provide outputs that are tradeable or saleable. Our definition of tradeable is that changes in one habitat can be compared to and traded for changes in another (i.e. offsetting or net gain). Whereas saleable is where measurable biodiversity units are created based on the metric. Very few of the reviewed metrics or approaches have been designed for these purposes.
All of the metrics were replicable, in that the same approach can be applied across different sites and contexts, even though the data and indicators used will vary. This contrasts with comparability across habitats and sectors. Performance against this criterion varied across the metrics. Some, such as the Agrobiodiversity Index, BIM, BMS and BPT are focused on the agriculture sector and use sector- or farm-specific indicators. Others that use MSA as an indicator are partially comparable, this is because MSA measures biodiversity relative to the undisturbed state of a habitat rather than the absolute amount of biodiversity. The Wallacea Biodiversity Units approach is also partially comparable as the suite of metrics varies across habitats, and it is not clear whether the resulting units can be compared.
Meaningfulness proved difficult to determine from the available information. Only one metric, BIRS, specifically mentioned that it aimed to be meaningful to a wide range of stakeholders. However, it might be inferred that metrics using common underlying measures such as MSA or PDF could be meaningful across stakeholders. Most of the metrics were mature with a history of application either of that tool or the underlying methodology. NARIA was not considered mature as it is currently in development.
| Name |
Clear, concise, transparent |
Scientifically robust: measurable |
Alignment: current or future policy objectives |
Alignment: current or future monitoring |
Tradeable |
|---|---|---|---|---|---|
| Agrobiodiversity Index |
P |
F |
F |
N |
N |
| Biodiversity Credits (Wallacea) |
P |
F |
P |
F |
|
| Biodiversity Footprint for Financial Institutions (BFFI) |
P |
F |
N |
N |
|
| Biodiversity Footprint Methodology (BFM) |
P |
F |
N |
N |
|
| Biodiversity Impact Metric (BIM) |
P |
F |
N |
N |
|
| Biodiversity Intactness Index |
F |
F |
F |
N |
N |
| Biodiversity Indicator and Reporting System (BIRS) Holcim |
F |
F |
N |
N |
|
| Biodiversity Indicators for Site-based Impacts (BISI) |
F |
F |
N |
N |
|
| Biodiversity Metric 3.1 |
F |
F |
N |
F |
|
| Biodiversity Monitoring System (BMS) |
F |
N |
N |
||
| Biodiversity Net Gain Calculator (BNGC) |
P |
F |
N |
N |
|
| Biodiversity Performance Tool (BPT) |
P |
F |
N |
N |
|
| BioScope |
P |
F |
N |
N |
|
| Corporate Biodiversity Footprint (CBF) |
P |
F |
N |
N |
|
| Exploring Natural Capital Opportunities, Risks and Exposure (ENCORE) |
P |
F |
N |
N |
|
| Global Biodiversity Score® (GBS®) |
P |
F |
N |
N |
|
| Global Impact Database (GID) |
P |
F |
N |
N |
|
| Integrated Biodiversity Assessment Tool (IBAT) |
P |
F |
F |
N |
|
| LIFE Methodology (LIFE) |
P |
F |
N |
N |
|
| Natural Asset Recovery Investment Analytics (NARIA) |
P |
F |
F |
N |
F |
| Norwegian Nature Index |
F |
F |
F |
N |
|
| Product Biodiversity Footprint (PBF) |
P |
F |
N |
N |
|
| ReCiPe |
P |
F |
N |
N |
|
| Species Threat Abatement and Restoration metric (STAR) |
P |
F |
F |
N |
|
| SSE Biodiversity Project Toolkit |
F |
F |
N |
F |
|
| The Biodiversity Integrated Assessment and Computation Tool (BINTACT) |
P |
F |
N |
N |
F - Full
P - Partial
N - None
No information
| Name |
Saleable |
Replicable |
Comparable across habitats and sectors |
Meaningful to all stakeholders |
Maturity |
|---|---|---|---|---|---|
| Agrobiodiversity Index |
N |
F |
N |
F |
|
| Biodiversity Credits (Wallacea) |
F |
F |
P |
P |
|
| Biodiversity Footprint for Financial Institutions (BFFI) |
N |
F |
F |
F |
|
| Biodiversity Footprint Methodology (BFM) |
N |
F |
P |
F |
|
| Biodiversity Impact Metric (BIM) |
N |
F |
N |
F |
|
| Biodiversity Intactness Index |
N |
F |
P |
F |
|
| Biodiversity Indicator and Reporting System (BIRS) Holcim |
N |
F |
F |
F |
|
| Biodiversity Indicators for Site-based Impacts (BISI) |
N |
F |
F |
||
| Biodiversity Metric 3.1 |
N |
F |
F |
P |
|
| Biodiversity Monitoring System (BMS) |
N |
F |
N |
||
| Biodiversity Net Gain Calculator (BNGC) |
N |
F |
P |
F |
|
| Biodiversity Performance Tool (BPT) |
N |
F |
N |
||
| BioScope |
N |
F |
F |
F |
|
| Corporate Biodiversity Footprint (CBF) |
N |
F |
P |
F |
|
| Exploring Natural Capital Opportunities, Risks and Exposure (ENCORE) |
N |
F |
P |
F |
|
| Global Biodiversity Score® (GBS®) |
N |
F |
P |
F |
|
| Global Impact Database (GID) |
N |
F |
P |
F |
|
| Integrated Biodiversity Assessment Tool (IBAT) |
N |
F |
F |
F |
|
| LIFE Methodology (LIFE) |
N |
F |
P |
||
| Natural Asset Recovery Investment Analytics (NARIA) |
F |
F |
F |
N |
|
| Norwegian Nature Index |
N |
F |
F |
F |
|
| Product Biodiversity Footprint (PBF) |
N |
F |
F |
F |
|
| ReCiPe |
N |
F |
F |
F |
|
| Species Threat Abatement and Restoration metric (STAR) |
N |
F |
F |
F |
|
| SSE Biodiversity Project Toolkit |
N |
F |
F |
P |
|
| The Biodiversity Integrated Assessment and Computation Tool (BINTACT) |
N |
F |
P |
F |
F - Full
P - Partial
N - None
No information
Corporate uses of biodiversity metrics
Many of the metrics reviewed in this report were developed for use by the corporate sector to inform both internal assessments of sustainability and impact on nature, and environmental reporting. The increasing interest in these assessments has also seen the development of formalised frameworks and recommended approaches. It is beyond the scope of this report to undertake a deep review of these frameworks. But we will briefly outline the measurement of biodiversity in the context of two emerging frameworks.
Taskforce on Nature-related Financial Disclosures (TNFD)[5] has developed a framework for identifying and reporting nature-related dependencies, impacts, risk and opportunities. The framework is intended to align with reporting requirements, allowing adaptability and increasing ambition in reporting as well as encouraging early uptake. TNFD sets out a LEAP (locate, evaluate, assess, prepare) process for evaluating environmental impacts and dependences. The TNFD is a framework rather than a standard and is not precriptive about how and whether biodiversity should be measured and reported. Guidance is provided on measuring both ecosystem and species condition (TNFD, 2022a) and example metrics (TNFD, 2022b). These metrics can include those based on Mean Species Abundance, Potentially Disappeared Fraction, IBAT and STAR, and BIRS as included in our preceding review. Direct measurement of species numbers and abundance are also suggested.
Corporate natural capital accounting approaches (e.g. as set out in the British Standards Institute's BSI 8632)[6] do not mandate the inclusion of biodiversity impacts or measurements in accounting frameworks. Instead, impacts and dependences are included according to the needs of the organisation and the decision contexts that will be informed by preparing accounts. For example, natural capital asset registers may list habitats, and risk registers the impacts of business operations on those habitats. The extent to which these measure biodiversity may vary depending on how close the business is to nature, i.e. land-based sectors may have readier access to biodiversity data.
Species information (numbers, abundance) may be included as non-monetised benefits from natural capital. An important issue is that biodiversity and ecosystem integrity can underpin a variety of other ecosystem services. Consequently, direct measurement and valuation of biodiversity carries a risk double counting within natural capital accounting approaches which typically quantify and value ecosystem services.
Contact
Email: katherine.pollard@gov.scot
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