The IUCN Red list includes all known amphibian species. However, there are limitations to the data, due mainly to incomplete knowledge of amphibians. The following details should be noted:
The rate of amphibian discovery remains very high, and the naming of new amphibian species continues at a rate of at least 50 species per year. Some parts of the world remain very poorly known in terms of their amphibian faunas, examples including the Guianas, Peru, Bolivia, West Africa, most of Central Africa, Angola, much of South and Southeast Asia (in particular the Western Ghats, Sri Lanka, the Himalayas, Myanmar, Laos, Cambodia, Vietnam, the Philippines, Sumatra, Kalimantan, Sulawesi, and the Maluku Islands), and New Guinea. In addition, many species names, especially in the tropics, actually represent complexes of several species that have not yet been disaggregated. In the IUCN Red List, these are treated as single species, pending resolution of their taxonomic status. With every update the intention is to include all newly described, however this is not always possible due to time and funding constraints, access to literature, and not being able to keep up to date with the very latest descriptions.
Because of the conservative approach taken to mapping species, the ranges for many species are likely to be minimum estimates. A rule was followed allowing interpolation of occurrence between known locations if the ecological conditions seem appropriate, but not permitting extrapolation beyond known locations. Some species are therefore almost certain to occur much more widely than has been mapped. Because of this, some regions are recorded as having much lower amphibian diversity than will eventually prove to be the case.
The information on the relative importance of different threatening processes to amphibian species is incomplete. In the amphibian assessments, we coded all threats that seemed to be having an important impact, but not the relative importance of such threats. For example, many species are known to have declined catastrophically in suitable habitats, but these are in most cases also subject to some sort of habitat loss. However, for these species, habitat loss appears at the moment to be a secondary threat, and the factors causing very rapid disappearance of populations, even in suitable habitats, appear to constitute the driving threats. Likewise, many species that have declined seriously because of over-harvesting are also subject to habitat loss, though over-harvesting is probably the dominant current threat.
In 2008 24.5% of amphibians were considered Data Deficient (DD). Because many DD species are likely to have small distributions or populations, or both, they are intrinsically likely to be threatened. Although the percentage of globally threatened or extinct amphibian species is already very high (32.4%), it is almost certainly an under-estimate of the real number. The data in the IUCN Red List, and the analyses resulting from it, therefore tend to under-estimate threat levels, probably very significantly. The results presented here are therefore the best estimates and predictions that can be made, based on incomplete information. Future updates of the data will almost certainly reveal higher levels of threat, and more serious declines.