One quarter of mammal species and 11 percent of bird species are threatened with extinction, says the 1996 IUCN Red List of Threatened Animals. The Red List, a document periodically up-dated since its first edition in the early 1960s, draws attention to the magnitude of the threat to biodiversity. The Red List's goal is to encourage decisionmakers to consider conservation of the biological diversity. George B. Rabb, chair of IUCN's Species Survival Commission, the commission which publishes the list, describes it as "a warning flag to nations and communities to pay much closer attention to the status of species". The 1996 IUCN Red List is the first-ever complete assessment of endangered mammal and birds, and the most comprehensive inventory yet of threatened species and subspecies on a global scale. The efforts of a network of almost 7,000 IUCN volunteers and data from BirdLife International, the World Monitoring Center, and The Nature Conservancy have resulted in the recognition of 5,205 animal taxa as threatened. Among mammals, the orders with the highest proportion of threatened species are rodents and bats. However, the highest number of threatened mammals is in the primate species including monkeys and apes. Of the bird species, the most threatened are the song birds. Crocodiles rank highest in the reptiles category and over 100 marine fishes have been added to the list in 1996.
Based on several scientific innovations which have enhanced its effectiveness as a conservation tool, the list assesses degrees of extinction threat according to new scientifically based quantitative criteria, better known as IUCN's Red List categories. "The newly developed criteria are the result of a controversial process that took five years and involved hundreds of SSC members," says Georgina Mace, the scientist who headed the process. The result is "both an explicit and transparent" system, allowing "a fair comparison among taxonomic groups and different regions of the world," adds Mace.
While the list is intended, as Rabb says, to be an "as objective and scientific as possible assessment" of the current status of animals, its "logical follow-up is to investigate the causes" and develop strategies to overcome them, argues Mace.
The most significant threat to the majority of species is "habitat reduction, fragmentation and degradation, reflecting human population growth combined with economic development," she notes. A "surprisingly important threat" is also the "introduction of non-native species".
While extinction is a natural process, the current extinction rate is "1,000 to 2,000 times faster" than the extinction rate shown by the fossil record, says Mace. This is mainly due to the fact that "a single species, man, is dominating the extinction process, unlike in the past."
The IUCN hopes to have all known species of higher vertebrates and freshwater fishes completely assessed within the next five to ten years. A longer period will be needed to asses the lower vertebrates and invertebrate species, due to their sheer magnitude and the lack of appropriate financial resources.
As another premiere, says Rabb, IUCN will launch later this year or early next year the first Red List of Threatened Plants.