Many species will experience distribution shifts and population declines
Results from studies across the world suggest that a high proportion of species are projected to experience shifts in their distributions and range contractions, and their populations may decline even faster. Many montane species will experience decreased populations as their ranges shift upslope, whereas sea level rise will imperil species restricted to low-lying islands.
Half of North American species are threatened by climate-induced range loss
In North America, modelling by National Audubon Society (BirdLife in the USA) shows that 53% of species are projected to lose more than half of their current geographic range by the end of the 21st century. For 40% of these species, loss occurs without concomitant range expansion. For others, loss of current range is coupled with the potential to colonize new areas. Based on these results, one-fifth of species are classified as ‘climate endangered,’ and another one-third of species are classified as ‘climate threatened.’
Most species will experience range contractions and shifts
Consistent results from studies by BirdLife and others across the world show that, on average, species are projected to experience 10-30% declines in their geographic range sizes, with 30-70% of their current distributions projected to become unsuitable by the end of the 21st century.
Some East African species are projected to lose all their suitable habitat by 2085
Bird communities in the Albertine Rift Valley of East Africa are likely to be forced upslope by an average of 350 m by 2085. Some areas in the valley are projected to support none of the endemic species by 2085, with at least one species—Red-collared Mountain-babbler (Kupeornis rufocinctus)—projected to lose all climatically suitable habitat in the region.
Sea-level rise will cause trouble for birds on low-lying islands in the Pacific
Species that are restricted to low-lying islands are particularly vulnerable to sea-level rise. In Oceania, seven species are entirely restricted to islands with a maximum elevation of 10 m, including the Critically Endangered Polynesian Ground-dove (Alopecoenas erythropterus). Sea level rise will also impact seabirds. For example, in Midway Atoll, Hawaii, a sea level rise of 2 m would flood 39-91% of Black-footed Albatross (Phoebastria nigripes) nests.