Measuring biodiversity: research into approaches

Results: Sense checking workshop

Poll results are integrated into Results: Metric 3.1 Applicability Scotland above. Key findings from the Padlet exercise are summarised below.

What should we avoid in a metric?

The inclusion of species provided some nuance in the comments. It was expressed that a metric should not focus on a single species as this misses out the measurement of broader ecosystem health. Species were considered important, suggesting that multiple species measures or indicators are desirable. Different taxa, however, operate at different spatial scales, with plant communities reflecting site level impacts whereas bird communities reflect landscape level impacts, this adds further complexity with the most appropriate species depending on the scale of impact. Given the urgency of developing a metric to inform decision making, delayed implementation whilst waiting for the ideal species measure should be avoided.

This latter point on urgency related to a broader theme of not immediately seeking perfection in a metric. A metric or tool should be able to evolve over time, reflecting changing guidance and advice. It should also recognise the importance of simpler habitats that can be easily restored or created. This contrasts with 'higher value' more complex habitats that may also be riskier to achieve. The metric should avoid being too prescriptive about how biodiversity uplift can be achieved. Approaches may need to differ across sites with general uplift better than very specific, focussed, improvements. Inflexibility was also raised as an issue with respect ecosystem changing in response to future drivers (e.g. climate change).

While both urgency and a need for flexibility came across as important, it was also recognised that there is a "need for robust sensitivity testing before publishing a metric/suite of metrics. Otherwise unintended consequences are possible". At site level, this may also need to consider what data are readily available or collectable. There is therefore the requirement to balance the urgent need for a metric, particularly within the Planning and Development sector, with ensuring that it is accurate and fit for purpose. The later will be crucial to ensure widespread adoption. Drawing on the experience of practitioners who are already utilising metrics to measure biodiversity net gain in Scotland would help identify potential issues that could be encountered.

The potential of under valuing habitats was raised with respect to both the importance of retaining existing habitat where possible (in a development context) and recognising the value of some degraded habitats with potential high innate biodiversity value such as native woodlands. The biodiversity value of transitional habitats was also mentioned as important, but not considered by existing metrics. In contrast, it was noted that encouraging lower condition or less distinctive habitat creation may encourage cheaper biodiversity credits, and should be avoided. The connectivity of existing habitats within their local contexts should also be considered. It is also recognised that simplification of landscapes is a key driver of biodiversity declines and there is a potential risk that if "one or two habitats 'gain more points' than others, this could create more homogenous and inappropriate restoration projects". Connectivity should also be included, avoiding a focus on site level action. It was recognised that this may not be immediately possible, but part of future updates to a metric as nature networks are developed. Consideration should therefore be given to ensure a landscape perspective is taken which focuses on spatially targeting a diversity of measures to optimise benefits gained.

Complexity was raised by several participants. A metric should be understandable and transparent to all users, not just ecological specialists. This was raised with respect to ensuring that the metric is understandable for planners who will be tasked with decision making based on the metric outputs. In contrast, it should not be too simplified, preventing it from capturing ecological processes and changes. Clearly it is important to get the balance right between ensuring that a metric is robust and that it provides a reliable and quantifiable way to measure biodiversity, against making sure that it is user-friendly with outputs that are meaningful to non-experts.

Linked to that, it should be possible to 'unpack' and 'look under the hood' to interrogate and analyse these processes, ideally in a way that does not exclude lay-persons understanding. This ties in with the findings of our first stakeholder workshop with all sectors prioritising the need for a metric to clear, concise and transparent. Transparency will be critical to avoid abuse and our stakeholder workshop highlighted concerns with respect to 'greenwashing' and 'gaming'.

Pros and cons: Risks associated with habitat creation

Habitat creation risks can be considered in terms of both the length of time required to achieve target condition and the impacts of how those risks are treate within a metric. These are summarised in Table 14. Longevity was raised as a concern from multiple perspectives with long-term management, monitoring and protection of habitats at risk particularly given changing tenure of both the site and adjacent areas. To ensure that changes in land use have positive effects for biodiversity outcomes should be monitored in the long term and action taken where shortfalls are identified. Climate risks could also be included in longer term assessments.

Standardisation of approaches to assigning risk was seen as both a potential pro and a con. If there is flexibility over risk factors, there is the potential for abuse. For example, from a developer's perspective altering risk multipliers to reflect a lower risk of habitat creation would result in a higher allocation of biodiversity units. There is also the potential to have standard multipliers as with Metric 3.1, but allowing greater flexibility to change these multipliers with justification given. However, any change would need verification to assess appropriateness and this would require additional resourcing from decision makers. Standardisation of assigning risk multipliers would help to prevent abuse and mitigate the need for additional verification. However, inflexibility means that risks cannot reflect site specific contexts but here changes could be made where supporting evidence is available. Standardisation also risks the use of similar approaches resulting in more readily achievable habitat types and measures.

There is the potential to assign some risk factors based on existing spatial datasets (e.g. elevation, aspect, soil type, deer numbers, hydrology) or simple drop down menus that could be easily verified (e.g. presence of deer fencing). Additional environmental information was also suggested. Indicators of soil health and condition could inform wider habitat condition.

The approach taken to assign risk should also not discourage action that is likely to yield the greatest benefits for biodiversity, even if these benefits take a while to come to fruition. Creation of more distinctive and better-quality habitats may be avoided due the higher risks and longer time frames associated with habitat creation. This was noted with respect to the current Metric 3.1 risk multipliers for peatland restoration and woodland creation. Consideration is needed to determine how risk multipliers integrate, to ensure that a metric incentivises the creation of good quality, highly distinctive habitats.

Pros and cons: Having a single metric across all sectors

The key themes that emerged from this question were around simplicity and standardisation, reflecting the complexity of ecological processes, and the needs of different sectors. These are summarised in Table 14

Standardisation was considered to have the advantage of providing consistency and comparability across sectors and applications allowing for a standardised means of trading or monetising biodiversity. Potentially, this would also aid understanding across end-users, allow for cross-sector training and cost-efficiency in governance. One stakeholder comment indicated "a single metric, used by all developers, planning authorities and other stakeholders in planning decisions, is required to ensure it is widely understood and applied to provide clarity and certainty for all users". Furthermore, a standardised approach would enable use to expand beyond development to encompass wider land use change.

However, it was also recognised that needs differ across sectors – "no one-size-fits all". The relative value or importance of habitats may vary across sectors, with other key differences including the scales of application and the skill levels of those undertaking assessment. Developers are more likely to engage ecological specialists, whilst the agriculture sector may rely on self-completion by farmers. Indeed, raising awareness of biodiversity through participatory monitoring and facilitating adaptive management to improve outcomes are key to the agricultural sector.

There was concern that adopting a single metric for all sectors could result in a lowest common denominator approach that may be oversimplified or general. One participant expressed the following concern "If one metric is designed to do too many things it will often dilute the primary purpose. Does it measure biodiversity, or food production, of people connection to nature (which can be detrimental to wildlife)".

The complexity of biodiversity and ecosystem functions was also reflected on as a reason why a one-size-fits all metric or approach may not always be appropriate. This included the need to consider wider ecological connectivity.

It was recognised that while a common approach should be taken, that this approach does not necessarily require a single metric. Instead, a standardised approach could be achieved through a suite of metrics tailored to sector needs.

Table 14: Pros and cons of habitat creation risks and a single metric

Risks associated with habitat creation

Pro

• Standardisation – flexibility in assigning risk multipliers can reflect site specific contexts
• Flexibility could encourage creation or restoraiton of more distinctive habitats

Con

• Longevity – changing land tenure on site and adjacent areas
• Long term monitoring required
• Standardisation – flexibility in assigning risk multipliers could result in abuse (over claiming units)
• Inflexibility could encourage creation or restoration of lower distinctivness habitats

Single metric

Pro

• Consistency and comparability across sectors
• Aid end-user understanding
• Cost-efficiency in governance and training

Con

• Differing sector needs
• Varying importance of habitats across sectors
• Differing scales of development and skill levels across sectors
• Lowest common denominator approach
• May not capture the complexity of biodiversity

What is important with respect to ecosystem health?

The main themes identified from this question were around ecosystem health. A healthy ecosystem can be characterised as having a high level of functioning (and thus capacity to deliver ecosystem services) and with the ability to withstand and spring back from external pressures. Ecosystem functioning was associated with terms such as integrity of ecosystem processes, condition and species richness and diversity. This indicates a broad-based measure is needed. Ecosystem health is closely related to functionality, with terms used including the 'degree of naturalness' and having a presence of taxa across trophic levels. Baselining was also mentioned as being necessary to understand what is healthy for a particular system.

Resilience was mentioned with respect to future environmental changes such as climate change. The need for long-term thinking to ensure "genuine uplift and long-term sustainability" was recommended. Biodiversity provides an insurance against environmental change, helping to safeguard the delivery of ecosystem services. In particular, the importance of soil biodiversity in underpinning ecosystem functioning was highlighted. Several comments recognised that habitats provide a range of ecosystem services including carbon storage, flood management, biodiversity, connectivity and heat regulation. With land being finite, we should capitalise on multi-functionality through stacking of ecosystem service delivery. Thought however needs to be given to how emerging markets (e.g. carbon and biodiversity) can be integrated and governed to ensure additionality whilst supporting multi-functionality (e.g. through a biodiversity uplift to carbon credits).

Linked strongly to resilience is the restoration of ecological connectivity and the creation of Nature Networks across Scotland. Enhancing connectivity facilitates dispersal, increasing genetic mixing between populations and reducing risks associated with inbreeding depression. Furthermore, connectivity facilitates movement through the wider countryside helping species meet their resource requirements and adapt to environmental pressures, including climate change.