Applying the New IUCN Threatened Species Categories

by Alison J. Stattersfield

Introduction

BirdLife International (formerly the International Council for Bird Preservation) has had a long history of involvement in the red-listing process, taking responsibility for advising IUCN and its Species Survival Commission on matters relating to the conservation status and needs of birds. BirdLife was among the first to apply the new IUCN threatened species categories in late 1993 and early 1994 (before the criteria were published), and was the first to evaluate a complete class of species.

Bird data for the Red Lists have come from the international Red Data Books, which have been a keystone of BirdLife’s research work. This program started with Vincent (1966-1971), was updated by King (1978-1979), then followed by regional treatments of Africa (Collar and Stuart 1985) and the Americas (Collar et al. 1992) (all using the old IUCN categories), and work is currently under way to assess candidates for Asia (using the new categories). Annotated global checklists, where data sources are referenced (Birds to Watch), have also been published (Collar and Andrew 1988, Collar et al. 1994; using old and new categories respectively) to keep the summary information and category allocation up-to-date, and to compensate for the time-lag caused by the detailed work necessary to produce an exhaustively researched Red Data Book.

The old IUCN system for identifying threatened species gave broad definitions for five threatened categories, of which only two directly indicated the likelihood of extinction. The new system (used to list all species in this Red List) is characterized by quantitative or clearly defined criteria, subcriteria and qualifiers, based around an evaluation of probabilities of extinction within specified time-frames. Species may qualify for one of three threatened categories depending on whether their abundance and/or range sizes, or rates of decrease in these, meet explicit numerical thresholds (see, for example, Mace 1993, Mace and Stuart 1994).

The aims of this essay are threefold. First, to draw on the experience of BirdLife’s research to discuss some of the particular difficulties which were experienced in applying the new IUCN threatened species categories to birds and to outline some potential solutions. Second, to use the BirdLife data to interpret the changes between successive Red Lists using the old and new categories. And third, to suggest how the red-listing process, using the new categories, can help conservation.

Some Problems and Solutions

One of the specific aims of the revision of the categories is to improve objectivity by providing clear guidance on how to evaluate different factors which affect the risk of extinction. For the majority of species—birds being no exception—numerical data concerning population numbers or rates of decline are lacking, or, at best, available on a site basis only (and thereby relevant to part of any population only). The preamble to the new categories therefore emphasizes the importance of attempting to classify poorly known taxa by estimating and extrapolating the current or potential threats into the future, and by allocating them a threat status by applying the precautionary principle.

Using inference in a consistent fashion, however, proved to be one of our greatest difficulties in producing the revised list for birds, for, despite the intentions of the new system, there is little guidance to help standardize this process. Indeed we found that there was considerable scope for variation in categorization of some species (using the same data) even between three people (my coauthors and I). Given that birds are the most comprehensively studied of all the classes of animals or plants, it is likely that inconsistencies arising from the use of inference will be far greater for those assessing less well known groups with fewer numerical clues, and in circumstances where more people contribute to the evaluation process.

Another dilemma we faced was the availability and quality of other data which could have helped us make well informed inferences. Despite access to many published sources of information and expertise from BirdLife’s extensive network of contacts, we found that our information on, for example, habitat loss and degradation was poor in some parts of the world. While evaluators can reasonably be expected to assemble all the appropriate species-specific material (on distribution, population, ecology etc.), they may not have access to general data concerning a species’s environment (e.g. logging activities or other land-use changes past, present, and planned). We recognized that some of our assessments might be seriously affected by ignorance of such key pieces of information (see Figure 1).

Other areas of difficulty, more fully discussed in Collar et al. (1994), included: the indistinct division between the near threatened and least concern categories; the appropriate use of the (non-threatened) conservation dependent category where information on important extrinsic factors such as the effectiveness of certain protected areas is needed; thresholds for the Critically Endangered category which could be (perhaps too) readily met by species with naturally small ranges as a result of any evidence indicating loss of habitat, however slight; an apparent inequity between species with small stable populations (= not threatened) versus those with much larger ones in the same area but with declining ones elsewhere (= threatened); and the definition of location which is crucial to the interpretation of the range-size criteria (see also, for example, Baillie et al. 1995, Hallingbäck et al. 1995 for difficulties encountered in applying the categories to different faunal groups).

Many of the above problems could be diminished by more detailed guidance in the use of the criteria (and a “Users’ Guide” is being prepared). This should be easier to formulate now, with many real examples, owing to the extensive collective experience of applying the categories for this Red List.

Further guidance will not, however, eliminate all the uncertainties associated with the use of inference. It is therefore vital that, where data are poor, the reasoning used to trigger certain criteria should be made as explicit as possible. Although the new system requires the inclusion of coding to indicate which criteria are judged to be met (rather than the category code alone), such notation could be misleading because there is no indication of levels of uncertainty. It is possible, because a species is classified as threatened using a system which is recognized as being more objective, to assume without question that the species meets the criteria (and has, for example, a population of less than 10,000 mature individuals) when, in fact, the original evaluation involved a highly precautionary inference derived from very slight evidence. Guesswork may therefore become fact, and judgements may not be re-evaluated from first principles in subsequent exercises. The only real solution, therefore, is to publish the species-specific and background data in detail, for example in Red Data Books, Action Plans, standard forms which ensure that all relevant details are logged, or interactive user-friendly computer programs with a comprehensive help system specially designed for this purpose. At the very least the mammal, reptile, fish and other equivalents of Birds to Watch (summarizing distribution, habitat requirements, abundance, trends and threats) should be produced as the documentary basis of future Red Lists.

Publication of data will have several benefits: critical inferences will be indicated and might generate more appropriately orientated fieldwork and important new information; details of the assessment will be available for more efficient and improved re-evaluation; and the documentation will allow for wide consultation and independent peer review, to aid consistency between treatment of poorly known species in different taxonomic groups and regions of the world. In addition, the environmental knowledge which has influenced judgements will be disclosed and rendered accessible to other assessors of species with similar ranges and problems. However, it is not efficient for different evaluators repeatedly to find the same environmental information, nor are they necessarily the best people to interpret it. An invaluable supplement to the forthcoming Users’ Guide, therefore, would be a common source of appropriate background data compiled and up-dated by relevant experts (see Figure 1).

Changes and Their Interpretation

Given the apparently major change in the categories and their criteria, one might expect big changes in the overall numbers and types of species listed as threatened. For birds, there has been an increase from 1,030 (Collar and Andrew 1988) to 1,111 (Collar et al. 1994). Although the net change is a relatively small one—an additional 81 species in total (= 8% increase)—more considerable flux is masked: 295 species were upgraded to threatened status (29%) and 214 species downgraded (21%). However, these changes may be attributed to four factors—the currently volatile nature of ornithological taxonomy (+81, -12), the inevitable improvement in knowledge (+157, -139), genuine changes in status (+14, -2) and changes in the criteria (+43, -61). If we assume that the first three factors are independent of the system used (accounting for 85% and 71% of the upgrades and downgrades respectively), it appears that the new categories have not radically altered the end result. It might be possible, therefore, to conclude that the old IUCN system for the classification of threatened species was adequate after all. However, as the use of inference is a key factor in the appropriate application of the new categories, the potential for misuse under the old system (where there were broad definitions only for guidance) was many times greater.

An interpretation of the changes between successive Red Lists, combined with the probabilities of extinction implicit in the new categories, allows us to make predictions of the rates of species’ extinctions. Such projections have been common in both the scientific and popular literature, and have caused much debate over the reality of the so-called impending extinction spasm (see, e.g. Myers 1987). We calculate that it would take between 800 and 2,800 years for half the world’s birds (4,850 species) to go extinct (Crosby et al. 1994). This is based on our categorization in Collar et al. (1994) and a dynamic projection that takes into account the likely changes in knowledge over the next 100 years and a rate of change of status equivalent to the one which we had perceived during the period 1988-1994 or worse. Under “normal” conditions, using mean survival times as illustrated from the fossil record, one would expect the natural time to extinction for half the world’s birds to be around 500,000 years. While we recognize that our models (which happen to be more optimistic than others based on older data and different methodologies, e.g. Smith et al. 1993) are not necessarily realistic, they clearly draw attention to a crisis of considerable magnitude, directly attributable to the destructive activities of man.

Using Red Lists

Red Lists are not an end in themselves. They provide information about the status of species, giving no indication of the conservation action which must be taken to save them from extinction.

The new guidelines state that the category of threat is not necessarily sufficient to determine priority ranking for conservation, and that a system for such assessments would include numerous other factors such as costs, logistics, and chances of success. Although these may be addressed in Action Plans, the increasing number of threatened species joining the Red Lists means that, for most (uncharismatic) species, the only real prospect for saving them is by site protection. Thus geographical areas of overlap between the thousands of threatened species included in this Red List (by country, area, and ideally site) would represent a new and vitally important basis for assigning the biological priorities for conservation action, and help to focus resources appropriately where choices have to be made (see Collar 1994).

As a result of its Red Data Book research, BirdLife has already identified key forests for threatened Afrotropical birds (Collar and Stuart 1988) and key sites for threatened Neotropical birds (Wege and Long 1995). These studies show that many threatened species occur together in similar places and that site-based priorities can therefore be developed effectively through threatened species analysis. BirdLife’s original Biodiversity Project extended this geographical approach by delimiting so-called Endemic Bird Areas (EBAs), covering the breeding ranges of all land bird species with restricted-ranges (including three-quarters of threatened species). The approach also demonstrated the importance of most of these areas for other endemic wildlife groups (ICBP 1992, Stattersfield et al. in prep.).

Current research at BirdLife focuses on Important Bird Areas (IBAs), which are selected on the basis of globally agreed criteria dealing with threatened species populations, importance for congregatory species, or representation of EBAs or larger biomes. The IBA initiative aims to cover the most important sites which will conserve all bird species for which a site-based approach is appropriate. IBAs have been identified for Europe (Grimmett and Jones 1989) and the Middle East (Evans 1994), and there is now a commitment to identify the majority of the world’s IBAs by the year 2000. Despite the fact that evidence for congruence exists, such an approach could be adopted by colleagues working on other groups, and help to polarize attention on key sites for all plant and animal “sympatric” species.

Conclusions

1. Where numerical species data are lacking, varying experience and interpretation of the new IUCN criteria coupled with ignorance of key environmental information, will result in inconsistent categorization of species’ status by different evaluators.

2. Consistency in categorization could be enhanced by a variety of measures including more detailed guidance in the use of the criteria, publication and referencing of key data, provision of sharing common sources of environmental information, greater consultation and independent peer review.

3. Although differences between the bird Red Lists using the old and new criteria are relatively small, the new system establishes a framework which reduces subjectivity and renders red-listing more accountable.

4. Conservation efforts can be aided and influenced by a reinterpretation of the species data collated for Red Lists to identify key sites, especially those which would protect large numbers of sympatric threatened species.

5. Changes between successive Red Lists could provide a useful measure of progress in the conservation of the world’s biodiversity.

Acknowledgements

This essay draws on the ideas and publications of many of my colleagues at BirdLife. I would like to thank Nigel Collar and Mike Crosby, in particular, for their encouragement and input, and also Colin Bibby, John Croxall, John Fanshawe, Adrian Long, and David Wege for helpful comments.

Alison Stattersfield
BirdLife International
Wellbrook Court
Girton Road
Cambridge CB3 0NA

References

Baillie, J., Callahan, D., and Gärdenfors, U. 1995. A closer look at the IUCN Red List categories. Species 25: 30-36.

Collar, N.J. and Andrew, P. 1988. Birds to watch: the ICBP world check-list of threatened birds. (Techn. Publ. 8). International Council for Bird Preservation, Cambridge, UK.

Collar, N.J. and Stuart, S.N. 1985. Threatened birds of Africa and related islands: the ICBP/IUCN Red Data Book. International Council for Bird Preservation, and International Union for Conservation of Nature and Natural Resources, Cambridge, UK.

—. 1988. Key forests for threatened birds in Africa. (Monogr. 3), International Council for Bird Preservation, Cambridge, UK.

Collar, N.J., Gonzaga, L.P., Krabbe, N., Madroño Nieto, A., Naranjo, L.G., Parker, T.A., and Wege, D.C. 1992. Threatened Birds of the Americas: the ICBP/ IUCN Red Data Book. International Council for Bird Preservation, Cambridge, UK.

Collar, N.J. 1994. Red Data Books, Action Plans and the need for site-specific synthesis. Species 21-22: 132-133.

Collar, N.J., Crosby, M.J., and Stattersfield, A.J. 1994. Birds to Watch 2: The World List of Threatened Birds. (BirdLife Conservation Series no. 4), BirdLife International, Cambridge, UK.

Crosby, M.J., Stattersfield, A.J., Collar, N.J., and Bibby, C.J. 1994. Predicting avian extinction rates. Biodiversity Letters 2: 182-185.

Evans, M.I. 1994. Important Bird Areas in the Middle East. (BirdLife Conservation Series no. 2), BirdLife International, Cambridge, UK.

Grimmett, R.F.A. and Jones, T.A. 1989. Important Bird Areas in Europe. (Techn. Publ. 9), International Council for Bird Preservation, Cambridge, UK.

Hallingbäck, T., Hodgetts, N., and Urmi, E. 1995. How to apply the new IUCN Red List categories to bryophytes. Species 24: 37-41

ICBP. 1992. Putting biodiversity on the map: priority areas for global conservation. International Council for Bird Preservation, Cambridge, UK.

King, W.B. 1978-1979. Red Data Book, 2: Aves. Second edition. International Union for Conservation of Nature and Natural Resources, Morges, Switzerland.

Mace, G.M. 1993. The status of proposals to redefine the IUCN threatened species categories. Guest essay in B. Groombridge, ed. 1994 IUCN Red List of Threatened Animals. International Union for Conservation of Nature and Natural Resources, Gland, Switzerland and Cambridge, UK.

Mace, G.M. and Stuart, S. 1994. Draft IUCN Red List categories. Species 21-22: 13-24.

Myers, N. 1987. The extinction spasm impending: synergisms at work. Conservation Biology 1: 14-21.

Smith, F.D.M., May, R.M., Pellew, R., Johnson, T.J., and Walter, K.S. 1993. Estimating extinction rates. Nature 364: 494-496.

Stattersfield, A.J., Crosby, M.J., Long, A.J., and Wege, D.C. In prep. Global directory of Endemic Bird Areas. (BirdLife Conservation Series), BirdLife International Cambridge, UK.

Vincent, J. 1966-1971. Red Data Book, 2: Aves. International Union for Conservation of Nature and Natural Resources, Morges, Switzerland.

Wege, D.C. and Long, A.J. 1995. Key Areas for threatened birds in the Neotropics. (BirdLife Conservation Series no. 5), BirdLife International, Cambridge, UK

© 1996 IUCN. Reprinted from the 1996 IUCN Red List of Threatened Animals.