Table 1: Numbers of threatened species by major groups of organisms (1996–2004)
 
Number of described species Number of species evaluated in 2006 Number of threatened species in 1996/98 Number of threatened species in 2000 Number of threatened species in 2002 Number of threatened species in 2003 Number of threatened species in 2004 Number of threatened species in 2006 Number threatened in 2006, as % of species described Number threatened in 2006, as % of species evaluated**
Vertebrates  
Mammals 5,416 4,856 1,096 1,130 1,137 1,130 1,101 1,093 20% 23%
Birds 9,934 9,934 1,107 1,183 1,192 1,194 1,213 1,206 12% 12%
Reptiles 8,240 664 253 296 293 293 304 341 4% 51%
Amphibians* 5,918 5,918 124 146 157 157 1,770 1,811 31% 31%
Fishes 29,300 2,914 734 752 742 750 800 1,173 4% 40%
Subtotal 58,808 24,284 3,314 3,507 3,521 3,524 5,188 5,624 10% 23%
Invertebrates  
Insects 950,000 1,192 537 555 557 553 559 623 0.07% 52%
Molluscs 70,000 2,163 920 938 939 967 974 975 1.39% 45%
Crustaceans 40,000 537 407 408 409 409 429 459 1.15% 85%
Others 130,200 86 27 27 27 30 30 44 0.03% 51%
Subtotal 1,190,200 3,978 1,891 1,928 1,932 1,959 1,992 2,101 0.18% 53%
Plants  
Mosses*** 15,000 93 --- 80 80 80 80 80 0.53% 86%
Ferns and allies*** 13,025 212 --- --- --- 111 140 139 1% 66%
Gymnosperms 980 908 142 141 142 304 305 306 31% 34%
Dicotyledons 199,350 9,538 4,929 5,099 5,202 5,768 7,025 7,086 4% 74%
Monocotyledons 59,300 1,150 257 291 290 511 771 779 1% 68%
Subtotal 287,655 11,901 5,328 5,611 5,714 6,774 8,321 8,390 3% 70%
Others  
Lichens 10,000 2 --- --- --- 2 2 2 0.02% 100%
Mushrooms 16,000 1 --- --- --- --- --- 1 0.01% 100%
Subtotal 26,000 3 --- --- --- 2 2 3 0.01% 100%
TOTAL 1,562,663 40,168 10,533 11,046 11,167 12,259 15,503 16,118 1% 40%
 
NOTES:
1) * It should be noted that for certain species endemic to Brazil, there was not time to reach agreement on the Red List Categories between the Global Amphibian Assessment (GAA) Coordinating Team, and the experts on the species in Brazil. The 2004 and 2006 figures for Amphibians displayed here 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 the assessments were found to be inconsistent with the approach adopted elsewhere in the world, and a "consistent Red List Category" was also assigned to these species. There was not time to agree these "consistent Red List Categories" with the Brazilian experts before the release of the IUCN Red List, therefore the original workshop assessments are retained here. However, in order to retain comparability between results for amphibians with those for other taxonomic groups, the data used in the Global Species Assessment (Baillie et al. 2004) are based on the "consistent Red List Categories". Therefore, figures in table 1 above will not completely match figures in table 2.1 in the Global Species Assessment.
2) ** Apart from the mammals, birds, amphibians and gymnosperms (i.e., those groups completely or almost completely evaluated), the figures in the last column are gross over-estimates of the percentage threatened due to biases in the assessment process towards assessing species that are thought to be threatened, species for which data are readily available, and under-reporting of Least Concern species. The true value for the percentage threatened lies somewhere in the range indicated by the two right-hand columns. In most cases this represents a very broad range. For example, the true percentage of threatened insects lies somewhere between 0.06% and 73%. Hence, although 41% of all species on the IUCN Red List are listed as threatened, this figure needs to be treated with extreme caution given the biases described above.
3) *** Mosses include the true mosses (Bryopsida), the hornworts (Anthocerotopsida), and liverworts (Marchantiopsida); while the ferns and allies include the club mosses (Lycopodiopsida), spike mosses (Sellaginellopsida), quillworts (Isoetopsida), and true ferns (Polypodiopsida).
4) Threatened species are those listed as Critically Endangered (CR), Endangered (EN) or Vulnerable (VU).
5) The numbers and percentages of species threatened in each group DO NOT mean that the remainder are all not threatened (i.e., are Least Concern). There are a number of species in many of the groups listed as Near Threatened or Data Deficient (see Tables 3a and 3b). These figures also need to be considered in relation to the number of species evaluated as shown in column two (see note 1 above).
6) The plant figures DO NOT include species from the 1997 IUCN Red List of Threatened Plants (Walter and Gillett 1998) as those were all assessed using the pre-1994 IUCN system of threat categorization. Hence the figures for numbers of threatened plants are very much lower when compared to the 1997 results. The results from this Red List and the 1997 Plants Red List should be combined together when reporting on threatened plants.

Sources for Numbers of Described Species:

Mammals – From Wilson and Reeder (in press), with deviations based on input from the IUCN/SSC Specialist Groups.
Birds – Provided by BirdLife International from their World Bird Database.
Amphibians – Provided by the Global Amphibian Assessment based on Amphibian Species of the World (Frost 2004).
Reptiles – Based on EMBL Reptile Database compiled by Peter Uetz - http://www.embl-heidelberg.de/~uetz/LivingReptiles.html. (Accessed 20 April 2006).
Fishes – Based on Froese, R. and Pauly, D. (eds) 2003. FishBase. World Wide Web electronic publication. www.fishbase.org. (Accessed 20 April 2006).
Invertebrates – From Groombridge and Jenkins (2002), but in turn largely based on Hammond (1992, 1995).
Mosses – Based on Hallingbäck and Hodgetts (2000).
Ferns and allies – Based on Groombridge and Jenkins (2002).
Gyymnosperms – Based on Donaldson (2003), Farjon (2001) and Mabberley (1997).
Dicotyledons and Monocotyledons – Based on Thorne (2002), but see Mabberley (1997); Schmid (1998); Govaerts (2001, 2003); Bramwell (2002); and Scotland and Wortley (2003) for alternative views on the numbers of seed plant species.