By Scott Hardy,
Our latest blog post is by Scott Hardy, in our Nature Conservation Policy and Advice Team. Following publication of a new Red List assessment, Scott tells us about the new report and discusses the importance of Red List assessments.
JNCC has recently published a new Great Britain Red List assessment for selected marine molluscs and echinoderms, commissioned from the Marine Biological Association (MBA) with funding support from NatureScot. This work forms part of a wider collaborative programme to produce national GB Red Lists across multiple taxonomic groups, working closely with the Country Nature Conservation Bodies (Natural England, NatureScot, and Natural Resources Wales). These assessments apply the globally recognised IUCN Red List Categories and Criteria to evaluate extinction risk at a regional scale.
Why Red Lists Matter
Red Lists offer a standardised approach to evaluating species’ risk of extinction, enabling comparisons across taxa and regions. For Great Britain, national Red Lists provide a shared evidence base that supports conservation agencies, researchers, and policymakers in identifying priorities and tracking progress.
The Red List assessments use data on species’ distribution and population trends against set criteria developed by the IUCN to assign one of the following categories:
- Critically Endangered (CR): Extremely high risk of extinction in the wild.
- Endangered (EN): Very high risk of extinction in the wild.
- Vulnerable (VU): High risk of extinction in the wild.
- Near Threatened (NT): Close to qualifying for a threatened category in the near future.
- Least Concern (LC): Widespread and abundant species.
- Data Deficient (DD): Insufficient information to assess extinction risk.
When combined with other evidence and expert input, GB Red Lists are a powerful tool. They help highlight species most at risk and identify knowledge gaps, which can inform strategic planning at national and local levels.
Citizen science is central to GB Red list assessments. Thousands of volunteers contribute wildlife records every year, providing essential raw data that underpins Red List assessments for many species. Their efforts are fundamental to understanding and protecting biodiversity, and we thank them for their continued efforts and skill.
The GB Red list status of our Molluscs and Echinoderms
The Molluscs and Echinoderms assessment reviewed 117 species, representing around 6% of molluscs and 4% of echinoderms known from British waters. Where assessment was possible, a significant number of the species were assessed as Least Concern reflecting wide distribution and no evidence of recent declines, however six species were assessed as Vulnerable to extinction, including:
- Ocean Quahog (Arctica islandica), a bivalve that can live for centuries but has declined in some areas due to bottom trawling.
- Purple Sea Urchin (Paracentrotus lividus), due to restricted distribution and suitable habitat, and vulnerability to disease and pollution.
- Several small snails and urchins with very restricted ranges, such as Boreotrophon clathratus and Strongylocentrotus droebachiensis.
A significant proportion of species were classed as Data Deficient, meaning there was insufficient information to assess extinction risk confidently against the IUCN criteria. The high number of Data Deficient assessments reflects the sparse records and identification challenges for marine invertebrates, many of which are small, cryptic, and difficult to survey.
Challenges in Marine Invertebrate Assessment
Assessing extinction risk for many marine species is complex. Marine habitats are expensive to monitor, requiring specialist equipment and vessels. Many species live buried in sediments or attached to deep-water substrates, making them hard to detect. Identification can be challenging, especially for small species that require microscopic examination or genetic analysis.
Even where records exist, they are often patchy and biased towards accessible areas such as rocky shores. For most species, population size and trends are unknown, and systematic monitoring is lacking. These limitations mean that applying IUCN criteria, such as thresholds for population decline or area of occupancy, often involves considerable uncertainty.
There is potential that advances in monitoring techniques, such as Environmental DNA (eDNA) sampling and automated image recognition, may offer opportunities to detect elusive species and fill some of these evidence gaps.
Why Data Deficiency Is Still Valuable
Data Deficient does not mean “not endangered” or “low priority”. It signals that we lack the evidence needed to make an assessment of extinction risk. Some Data Deficient species may be widespread but poorly recorded, others may be naturally rare yet stable, some may genuinely be at risk of extinction. Data Deficient assessments highlight where knowledge gaps exist and can help inform where future research could focus. Understanding which species lack data helps direct monitoring efforts and investment in new technologies.
Looking Ahead
This assessment is part of collaborative programme between the GB statutory nature conservation bodies (JNCC, Natural England, Natural Resources Wales, and NatureScot) producing GB national IUCN red list across multiple taxonomic groups. While this work is collaborative, Natural England has played a major role in expanding the number of GB Red List assessments. This reflects their commitment to improving biodiversity evidence to support England’s environmental targets, including those set under the Environment Act and the biodiversity indicator framework.
JNCC currently shares GB Red List data via the conservation designation spreadsheets, which also contains information on whether species are listed in international agreements, UK legislation, and UK country lists. We’re excited to be working on a new update of the designation database, bringing the data up to data, and making the data even more usable. This work includes improving how Red List information is shared and used.
Following a recent survey of Red List data users, we are working with the Country Nature Conservation Bodies to modernise the way assessment data is shared on our website, so watch this space!
Explore the Full Report
The full assessment, including detailed species accounts and methodology, is available in the form of a JNCC report (JNCC Report 805: IUCN Red List of selected molluscs and echinoderms in Great Britain). We encourage readers to explore the report and learn more about the status of these fascinating species.
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