The Red List Index for the birds in different biogeographic realms for 1988–2012

Red List Index (RLI) of species survival for bird species in different biogeographic realms (n = 1,712 non-Data Deficient Palearctic species, 962 Nearctic, 2,234 Afrotropical, 4,043 Neotropical, 2,181 Indomalayan, 38 Australasian and 2,106 Oceanic species) showing the proportion of species expected to remain extant in the near future without additional conservation action. Source: Analysis of data held in BirdLife’s World Bird Database (2012).

The Red List Index (RLI) for birds (Butchart et al. 2004, 2005, 2007) can be broken down by biogeographic realm to compare trends in different parts of the world. The results show that species have deteriorated in status in all regions, but there are some clear regional variations. Birds in the Oceanic realm are substantially more threatened on average (with lower RLI values) and have declined fastest, often owing to the detrimental impacts of invasive alien species on Pacific islands. In the Indomalayan realm, there was a sharp decline in the status of birds in the 1990s. This was a result of the intensifying destruction of forests in the Sundaic lowlands of Indonesia, which escalated particularly in the late 1990s. Such large-scale habitat loss has obvious implications for the extinction risk of the many bird species that are largely restricted to these forests.

Interpreting the RLI
An RLI value of 1.0 equates to all species being categorised as Least Concern, and hence that none are expected to go extinct in the near future. An RLI value of zero indicates that all species have gone Extinct. Species are included in the calculations for all biogeographic realms in which they occur regularly, but status changes driving RLI trends are assigned only to the realm(s) in which the processes driving them occurred.