Biological Conservation 149 (2012) 145–146 Contents lists available at SciVerse ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Letter to the Editor The growing availability of invertebrate extinction risk assessments – A response to Cardoso et al. (October 2011): Adapting the IUCN Red List criteria for invertebrates Drawing on a case study of 48 species of Azorean arthropods and Iberian spiders, Cardoso et al. (2011) evaluate the efficacy of the IUCN Red List for assessing the extinction risk of invertebrate species. They recommend alterations to the current Red Listing criteria, specifically to accommodate invertebrates. Cardoso et al. identify two key problems that they see preventing extinction risk evaluation in invertebrates, stating ‘‘the current [IUCN Red List] criteria are difficult to apply using the information that can be reasonably gathered for most invertebrate species’’, and noting ‘‘a bias [in current Red List coverage of invertebrates] towards large species with wide distribution ranges and high dispersal abilities’’. These are both incorrect. In recognition of the lack of invertebrate coverage on the Red List, a project was designed and implemented to provide meaningful, cross-taxon information on relative risk of extinction (the sampled approach to Red Listing: Baillie et al., 2008; Collen and Baillie, 2010). Invertebrate groups for which assessments have been recently produced include butterflies, cephalopods, crayfish, lobsters, dragonflies, dung beetles, freshwater crabs, freshwater molluscs and reef building corals, which will result in >15,000 new invertebrate species assessments (more than one third of the total species listed on the Red List at the start of the project). Taking a representative sample across these groups ensures that due coverage is given to the small bodied species with narrow ranges, within those groups. Moreover, related projects targeted at marine and freshwater taxa are similarly contributing to an ever-increasing representation of invertebrates on the Red List. While we fervently agree that there is a need to tackle the four shortfalls that Cardoso et al. (2011) identify as limiting for understanding of invertebrate biology, we strongly disagree that it is difficult to gather enough information to classify most species into any risk category. The current coverage of non-vertebrates on the Red List still falls well short of what is desired; however, the 27,337 [data downloaded from www.iucnredlist.org on 21st November 2011] non-vertebrate assessments currently available (12,562 of which are listed in threatened categories) are testament to the fact that it is possible to classify them. While it is true that there are often less data available for invertebrate species than their vertebrate counterparts, from the groups that we have so far assessed under the sampled Red List project, we have found levels of Data Deficiency to be marginally higher (32%, mainly brought about by current high rates of Data Deficiency in freshwater crabs, which are likely to be reduced in future reassessments following intensified data collection), but broadly similar to those in vertebrates (excluding birds, where 0006-3207/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2012.02.007 the level of data deficiency is exceptionally low in comparison to other groups). Overall, around 27% of invertebrates currently listed on the Red List are classed as Data Deficient, which is comparable to amphibians and marine fishes, and far lower than those observed for sharks and rays. A common difficulty that is faced by risk assessment schemes such as the Red List is how to ensure that all species, despite wide variation in life history and ecology, are assessed equitably. This is important if, for example, we are to draw conclusions about relative levels of risk across groups. IUCNs decision to focus on a single set of criteria for all species was born of the recognition that life history, rather than taxonomic affiliation, was probably the appropriate way to classify species for assessment (Mace et al., 2008). The alternative approach necessitates that criteria become long and complicated with bespoke sets of parameters and rules for different taxa. These are undesirable qualities, particularly given that extinction risk assessments that require comparable approaches across taxa, are being used on ever wider platforms to inform policy relevant biodiversity targets (e.g. Convention on Biological Diversity 2020 Aichi Targets, United Nations Millennium Development Goals). Rather than constantly tweaking at risk evaluation criteria, a more concerted effort to systematically add species from under-represented groups to the Red List would result in far greater impact on non-vertebrate species coverage, and we feel would do far more to further our collective understanding of extinction risk in invertebrates. Contrary to Cardoso et al., we believe that the approach currently taken under the IUCN framework is biologically and operationally the most rational and effective. Successful implementation of risk evaluation criteria for invertebrates, regardless of the type, depends crucially on appropriate transformation of admittedly limited data from different species. Relevant and comparable values of key parameters are used to evaluate against the criteria thresholds. These key terms used in IUCN definitions have received much less critical external review than have the numerical thresholds in the criteria. It is likely that variation in the application of these definitions across taxonomic groups are often more significant in misclassification of species. References Baillie, J.E.M., Collen, B., Amin, R., Akcakaya, H.R., Butchart, S.H.M., Brummitt, N., Meagher, T.R., Ram, M., Hilton-Taylor, C., Mace, G.M., 2008. Towards monitoring global biodiversity. Conserv. Lett. 1, 18–26. Collen, B., Baillie, J.E.M., 2010. The barometer of life: sampling. Science 329, 140. Mace, G.M., Collar, N.J., Gaston, K.J., Hilton-Taylor, C., Akcakaya, H.R., LeaderWilliams, N., Milner-Gulland, E.J., Stuart, S.N., 2008. Quantification of extinction risk: IUCN’s system for classifying threatened species. Conserv. Biol. 22, 1424– 1442. 146 Letter to the Editor / Biological Conservation 149 (2012) 145–146 Ben Collen Monika Böhm Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, United Kingdom Tel.: +44 (0)207 449 6642. E-mail address: ben.collen@ioz.ac.uk (B. Collen) Available online 27 March 2012