Our most recent blog post is from Tree Robinson, Biodiversity Indicators Adviser. Tree outlines the collaborative process involved in developing an indicator.
As part of the UK’s response to the Convention of Biological Diversity and our reporting under the Global Biodiversity Framework (GBF), JNCC and Defra together were required to develop and publish headline indicator A.4, snappily titled "The proportion of populations within species with an effective population size of > 500".
Conservation genetics is a vital and rapidly developing area of work, based on the understanding that the maintenance of genetic diversity is an essential aspect of conservation, and that maintaining species numbers has little value if those individuals have no diversity. Scientific theory suggests that a population of around 500 adults is required to effectively maintain on genetic diversity in the next generation; but as not all individuals breed, a general rule of thumb equates this to a census size of 5,000.
The calculation sounds straightforward enough, but the best possible version of this indicator should include several hundred species and be fully representative of the breadth of UK biodiversity. Completing this number of assessments was well outside the capabilities of the headline indicator team, as JNCC was working in parallel on several new headline indicators in 2025, alongside producing the existing UK Biodiversity Indicators. So, how could we develop a brand-new indicator, maximising the quantity and quality of data included, and ensuring the impact of the publication?
NatureScot stepped in to offer support. They informed us that, as part of a project with the Royal Botanic Garden Edinburgh, and the University of Edinburgh, funded by the Scottish Environment, Food and Agriculture Research Institutions, they were planning on not only refreshing their Genetic Scorecards for Scottish species but also had the capacity to add more species, and to expand the assessments to cover the whole of the UK. The group included conservation genetics experts, and others with the skills necessary to code and analyse the vast amount of data we were expecting.
This provided us with part of the answer for this indicator, and we were incredibly grateful. Next steps were to work out how to coordinate the group of more than 20 people who contributed assessments, how to ensure standardisation across the assessments, and, possibly most importantly, how to choose which species to include.
So, over the following weeks we researched a range of recommendations for choosing species, and finally selected a list based on taxonomic groups, ecology, and criteria specific to genetic conservation issues such as populations which are harvested or hunted. Then across two ambitious, intense and ultimately highly productive days in Edinburgh, we hashed out details of the approach for assessments and allocated them to the team.
Ultimately, the group was able to complete detailed assessments for 43 species in the indicator, spanning 11 taxonomic groups and including iconic species such as red squirrel Sciurus vulgaris, golden eagle Aquila chrysaetos and bluebell Hyacinthoides non-scripta, as well as less well-known but vitally important species like purple moor-grass Molinia caerulea, and common species like stock dove Columba oenas.
Working together also enabled consensus on some tricky issues around defining populations, which can be challenging; some species which are highly mobile and have a wide distribution across the UK might function as a single population, while others which are less mobile may be much more fragmented. The assessments were therefore flexible and allowed a range of population definitions, but adequate data were not available for some species which had been selected. Some species were replaced by similar species for which data was available, but others demonstrate knowledge gaps and may guide future work to understand that species more.
The indicator result was that, on average across these species, 64% of their populations have an effective size above 500 individuals. As we report on this indicator over time, this first value will form the first in a time series which will be informative, and conservation actions taken by the UK will be able to influence the outcome. For example, if the smaller population of smooth snake Coronella austriaca increases to more than 5,000 (which is an effective population size of 500), the individual value for this species will increase from 0.5 to 1, and will raise the average value across the indicator.
However, care must be taken when interpreting such headline values. For the next iteration of this indicator, we will aim to include more species to provide a wider picture of the genetic diversity of wild species in the UK. However, if any new species are of conservation concern with small populations, their assessments will likely reduce the overall headline value while still increasing the overall representativeness and value of the indicator. The Scottish Genetic Scorecards contain a broader picture of species conservation, and the scorecards may be expanded in the future to cover more species.
The process of collaborating on this indicator with such a broad group of experts has allowed us to publish an indicator for the UK, now named ‘Genetic Diversity of Wild Species’ which has genuine value, and will feed into the global conservation picture which the GBF aims to build. We look forwards to working together again for the next iteration of this indicator.
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