Three Decades of Classifying Threatened Species: Lessons Learned from and about the IUCN Red List Criteria for Quantifying Extinction Risk

Authors

• H. Resit Akçakaya, Stony Brook University
• E. J. Milner-Gulland, University of Oxford
• Mike Hoffmann, IUCN Species Survival Commission
• Helen M. Regan, IUCN Species Survival Commission
• Ilona Naujokaitis-Lewis, IUCN Species Survival Commission
• Andre E. Punt, University of Washington - Seattle Campus
• Kevin J. Gaston, University of Exeter
• David A. Keith, IUCN Species Survival Commission
• Stuart H. M. Butchart, University of Cambridge
• Simon N. Stuart, IUCN Species Survival Commission
• Nigel J. Collar, IUCN Species Survival Commission
• Moreno Di Marco, IUCN Species Survival Commission
• Monika Bohm, IUCN Species Survival Commission
• Alex J. Berryman, IUCN Species Survival Commission
• David P. Mallon, Manchester Metropolitan University
• Axel Hochkirch, University of Trier
• Nicholas K. Dulvy, Simon Fraser University
• Malin Rivers, Botanic Gardens Conservation International
• Thomas M. Brooks, IUCN Species Survival Commission
• James R. S. Westrip, IUCN Species Survival Commission
• Jonathan Paul Rodriguez, IUCN Species Survival Commission
• Craig Hilton-Taylor, IUCN Species Survival Commission
• Janet Scott, IUCN, The David Attenborough Building, Cambridge
• Simon Tarr, IUCN, The David Attenborough Building, Cambridge
• Sophie H. Ledger, IUCN Species Survival Commission
• Christi Linardich, Old Dominion UniversityFollow

Document Type

Article

Publication Date

2026

DOI

10.1098/rspb.2026.0316

Publication Title

Proceedings of the Royal Society B Biological Sciences

Volume

293

Issue

2074

Pages

20260316

Abstract

The IUCN Red List of Threatened Species, the most widely used global system for assessing species' extinction risk, has become a foundational source of information for conservation management, policy and research. Since the adoption of quantitative extinction risk criteria more than three decades ago, the Red List has expanded substantially in scope and influence, informing decisions ranging from species conservation and protected area designation to international agreements, corporate risk assessments and global biodiversity indicators. Given its central role, maintaining scientific rigour, transparency and trust in the Red List system is essential. Feedback from users, emerging from evolving applications and scientific advances, has shaped the Red List throughout. At the same time, the Red List has been subject to recurring critiques, some of which stem from persistent misconceptions about its purpose, design and appropriate use. To address these, we review the history and development of the Red List system, clarify the strengths of its design, delineate the contexts for which the system was and was not intended, and elucidate the circumstances under which it may be modified. Finally, we outline pathways for researchers and users to contribute to ongoing improvements and discuss potential future directions for evolution of the Red List.

Rights

© 2026 The Authors

Published by the Royal Society under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits unrestricted use, provided the original author and source are credited.

Data Availability

Article states: "Supplementary material is available online [113]."

Original Publication Citation

Akçakaya, H. R., Milner-Gulland, E. J., Hoffmann, M., Regan, H. M., Naujokaitis-Lewis, I., Punt, A. E., Gaston, K. J., Keith, D. A., Butchart, S. H. M., Stuart, S. N., Collar, N. J., Di Marco, M., Bohm, M., Berryman, A. J., Mallon, D. P., Hochkirch, A., Dulvy, N. K., Rivers, M., Brooks, T. M.,…Linardich, C. (2026). Three decades of classifying threatened species: Lessons learned from and about the IUCN Red List criteria for quantifying extinction risk. Proceedings of the Royal Society B Biological Sciences, 293(2074), Article 20260316. https://doi.org/10.1098/rspb.2026.0316 

Repository Citation

Akçakaya, H. Resit; Milner-Gulland, E. J.; Hoffmann, Mike; Regan, Helen M.; Naujokaitis-Lewis, Ilona; Punt, Andre E.; Gaston, Kevin J.; Keith, David A.; Butchart, Stuart H. M.; Stuart, Simon N.; Collar, Nigel J.; Marco, Moreno Di; Bohm, Monika; Berryman, Alex J.; Mallon, David P.; Hochkirch, Axel; Dulvy, Nicholas K.; Rivers, Malin; Brooks, Thomas M.; Westrip, James R. S.; Rodriguez, Jonathan Paul; Hilton-Taylor, Craig; Scott, Janet; Tarr, Simon; Ledger, Sophie H.; and Linardich, Christi, "Three Decades of Classifying Threatened Species: Lessons Learned from and about the IUCN Red List Criteria for Quantifying Extinction Risk" (2026). Biological Sciences Faculty Publications. 706.
https://digitalcommons.odu.edu/biology_fac_pubs/706