Nectophrynoides viviparous (a frog), Tanzania / Photo by © David Moyer – Wildlife Conservation Society

Description of Data

The Global Amphibian Assessment includes data on each of the 5,918 amphibian species currently known to science (as of the end of 2005). The types of data included on this website are described below. The process of collecting and reviewing the data and making the assessments is described in About the GAA.

Data Types
Limitations of the Data

1. Data Types

1.1 What data are available from the searchable online database

The following data are provided for each species in the online searchable database:

Species, genus, family, order, taxonomic authority, commonly-used synonyms, English and other common names (if any), and taxonomic notes (if needed, normally used to clarify difficult or confusing issues). The GAA uses Amphibian Species of the World as its default taxonomy, and only departs from this in a few justified circumstances.

1.1.2 General Information

General text information on: geographic range, population (usually a subjective assessment of abundance in the absence of quantitative information), habitat and ecology (including both breeding and non-breeding habitats, and breeding strategy [i.e., larval development, direct development, viviparous], major threats and conservation measures (in particular noting occurrence in protected areas).

1.1.3 Red List Assessment

Based on the information above, the following is determined: IUCN Red List Category, IUCN Red List Criteria, Rationale for the Red List assessment, reason for any change from previous assessments (i.e., genuine change in status of species, new or better information available, incorrect information used previously, taxonomic change affecting the species, previously incorrect application of the Red List Criteria), current population trend (i.e., increasing, decreasing, stable, unknown), date of assessment, names of assessors, and any notes relating to Red Listing (e.g., any important issues in deciding the Category). It should be noted that for certain species endemic to Brazil, it has not yet been possible to reach agreement on the Red List Categories between the GAA Coordinating Team, and the experts on the species in Brazil. The Red List Categories displayed are those that were agreed at the GAA Brazil workshop in April 2003. However, in the subsequent consistency check conducted by the GAA Coordinating Team, many of these were found to be inconsistent with the approach adopted elsewhere in the world. Under the notes on Red Listing, the likely consistent Red List Category is given for these species, and it is these consistent Red List Categories that are used in the analysis under the GAA Key Findings presented here.

1.1.4 Distribution Map

A geographic distribution map (in shapefile [.shp] format) of the Extent of Occurrence for each species. The maps are in the form of polygons that join known locations. A species' distribution map can consist of more than one polygon where there is an obvious discontinuity in suitable habitat. Metadata attached to each polygon include the current status (e.g. extant, extirpated) and origin (eg. native, introduced, re-introduced). A list of countries of occurrence is given, noting whether it is native extant, extinct, introduced and/or re-introduced.

The GAA includes distribution maps for 5,816 of the 5,918 amphibian species. Maps are missing for species that are known only from non-specific type localities.

1.1.5 Habitat Preferences

Each species is coded against a standardized list of habitats, the IUCN Habitat Authority File.

1.1.6 Major Threats

Each species is coded against a standardized list of threats, the IUCN Major Threat Authority File, and coded for whether the threat is acting in the past, present or future, or is an ongoing threat.

1.1.7 Conservation Actions

Each species is coded against a standardized list of conservation actions, the IUCN Conservation Actions Authority File, and coded for whether this measure is "In Place" or "Needed".

1.1.8 Utilisation

Each species is coded against the IUCN Utilisation Authority File (focusing on the purpose/type of use, the primary forms removed from the wild, and the source of specimens in commercial trade).

1.1.9 Bibliography

A listing of important references for each species.

1.2 Limitations of the Data

The GAA is a comprehensive dataset covering all known amphibian species (as of the end of the 2005). 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 Indochinese countries, 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 GAA, these are treated as single species, pending resolution of their taxonomic status.

Because of the conservative approach taken in the GAA 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 GAA, 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.

The percentage of Data Deficient species (23.4%) is very high compared to mammals (5.3%) and birds (0.8%). Because many Data Deficient 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 (32.6%), it is almost certainly an under-estimate of the real number. The data in the GAA, 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 GAA will almost certainly reveal higher levels of threat, and more serious declines.