Editing IPCC:AR6/WGII/Cross-Chapter-Paper-1 (section)

===== CCP1.2.1.1.2 Observed impacts on biodiversity =====

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Although conservation status has only been assessed globally for about 6% of all species ( [[#Costello--2019|Costello, 2019]] ) and most confirmed extinctions and threatened species are terrestrial, a higher proportion of freshwater species are threatened. This is reflected in the higher proportion of freshwater hotspots impacted by humans ( [[#Collen--2014|Collen et al., 2014]] ; [[#Costello--2015|Costello, 2015]] ; [[#Harrison--2018|Harrison et al., 2018]] ). The rate of species endemicity is exceptionally high in freshwater biogeographic realms (i.e., large regions of distinct species composition and endemicity), at 89–96% for fish in all but one realm, compared to 11–98% for terrestrial vertebrate groups ( [[#Leroy--2019|Leroy et al., 2019]] ) and 17–84% for marine realms ( [[#Costello--2017|Costello et al., 2017]] ). Already, one-third of wetlands have been lost and 9000 freshwater species are threatened with extinction without considering the effects of climate change ( [[#Darwall--2018|Darwall et al., 2018]] ), and only 13% of world rivers were recently classified as least impacted ( [[#Su--2021|Su et al., 2021]] ).

Globally, observed climate-driven changes in biodiversity are typically of species distributions shifting to higher latitudes ( ''virtually certain'' ) ( [[#Lenoir--2020|Lenoir et al., 2020]] , Ch.2, Ch. 3.4). Since the 1950s, marine species richness has shifted poleward in the Northern Hemisphere, increased in mid-latitudes and declined at the equator in concert with ocean warming ( ''medium confidence'' ) ( [[#Chaudhary--2021|Chaudhary et al., 2021]] ). Climate-driven altitudinal shifts are common on land ( ''high confidence'' ) ( [[#Lenoir--2015|Lenoir and Svenning, 2015]] ; [[#Steinbauer--2018|Steinbauer et al., 2018]] ), and depth shifts in the ocean may occur but are little studied ( ''low confidence'' ) ( [[#Burrows--2019|Burrows et al., 2019]] ; [[#Jorda--2020|Jorda et al., 2020]] ). While climate-induced range expansions can be viewed as opportunities for increasing regional biodiversity, range contractions adversely affect biodiversity through regional extirpations ( ''high confidence'' ) ( [[#Cahill--2013|Cahill et al., 2013]] ; [[#Chaudhary--2021|Chaudhary et al., 2021]] ).

Both of the two climate change associated global species extinctions to date support the predictions that endemic species on mountains and islands are at the greatest risk of extinction ( [[#Manes--2021|Manes et al., 2021]] ). The golden toad ( ''Bufo periglenes'' ) became extinct after some years of decline associated with changes in climate warming and precipitation in the Talamancan-Isthmian Pacific Forests biodiversity hotspot (H22) ( [[#Pounds--1999|Pounds et al., 1999]] ; [[#Cahill--2013|Cahill et al., 2013]] , WGII Ch2.4.2.2). The Bramble Cay melomys ( ''Melomys rubicola'' ) '','' a rodent endemic to an island between Australia and Papua New Guinea and closely related to a mainland Australian species, became extinct due to habitat loss arising from climate change-related sea level rise and cyclone activity ( [[#Fulton--2017|Fulton, 2017]] ; [[#Roycroft--2021|Roycroft et al., 2021]] , WGII Ch.11).

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