The IUCN Red List is produced and managed by the international IUCN Global Species Programme and the Species Survival Commission (SSC).
The IUCN Red List System was first conceived in 1964 and set a standard for species listing and conservation assessment efforts. For more than 30 years the Species Survival Commission (SSC) in conjunction with the IUCN Species Programme, has been evaluating the conservation status of species and subspecies on a global scale – highlighting those threatened with extinction and promoting their conservation.
Over time, however, IUCN recognised that a more objective and scientific system for determining threat status was needed, one that drew on advances in the science of conservation biology and other disciplines. There was also a need for a more accurate system for use at the national and regional level. The IUCN Red List Categories evolved over a four-year period through extensive consultation and testing with more than 800 SSC members, and the wider scientific community. The more precise and quantitative Red List Categories and Criteria were adopted by IUCN in 1994.
In 1988 all bird species were evaluated, and in the 1996 IUCN Red List of Threatened Animals the conservation status of every mammal species in the world was assessed for the first time. These were major milestones in conservation because not only was the overall status of mammals and birds determined, but a baseline was established from which to monitor future trends.
For the 1996 list 5,205 species were evaluated resulting in 25% of all mammals and 11% of all birds being listed as threatened.
In 2011 there were over 61,000 species on the Red List and all mammals, birds, amphibians, sharks, reef-buliding corals, cycads and conifers had been assessed.
The present IUCN Red List is found here.
The Guardian has a useful summary – this is here.