Assessing Climate Change Vulnerability of Breeding Birds in Arctic ...

Section 3. ResultsHere we present a general summary of thevulnerability scores for the 54 bird speciesbreeding in Arctic Alaska, and how thecomponents of vulnerability evaluated bythe CCVI (direct climate exposure, indirectexposure, and sensitivity) contributeddifferentially to the results. For a detailedlook at the factors influencing thevulnerability of particular species, see theindividual Species’ Accounts in AppendixB.Climate exposureThe CCVI uses future temperature andmoisture changes generated by GCMs. Themagnitude of projected temperature changeis great for many northern latitudes, and theregion of the Arctic LCC in Alaska is noexception. The projected warming for 2050(2040-2069 average) for all emissionscenarios and models exceeded +3.1 o Cacross the Arctic LCC region. For 23 of the54 species, temperature exposure for the2050 timeframe was +4.3 o C or greater forthe A1B SRES emissions scenario andcomposite of all five SNAP climate models.The ranges of these 23 species weregenerally restricted to the north-central andwestern parts of Alaska’s Arctic LCCregion.Projected changes in moisture (asmeasured by the Hamon AET:PET aridityindex) between the historical and future timeperiod were minimal, regardless of emissionscenario or GCM model used. Themagnitude of moisture changes for allspecies fell in the CCVI’s lowest category,having little direct negative influence on thespecies’ vulnerabilities reported below.However, the low magnitude of moisturechange does temper the impact of the highmagnitude of temperature, moderating itsinfluence on the eight sensitivity factorsweighted by the combined exposure.Indirect exposureIn a region with a relatively light humanfootprint and few anthropogenic barriers towithin range movement or shifts, only 3 ofthe 4 indirect exposure factors were relevantto northern Alaska: sea level rise, naturalbarriers to dispersal, and human responses toclimate change. Sea level rise (SLR) andother disturbances linked to storminessduring the lengthening open-water season(e.g., erosion and wash-over) have thepotential to strongly affect species that usecoastal habitats. The CCVI separates itsevaluation of these influences by using aGIS overlay for SLR, and a qualitativeevaluation of species’ sensitivity toassociated disturbances. Only seven of thebird species we examined (Brant, SnowGoose, Steller’s Eider, Buff-breastedSandpiper, White-rumped Sandpiper,Dunlin, and Common Eider) will potentiallylose 10% or more of their range in theAlaska portion of the Arctic LCC toinundation under a 2-m SLR scenario.We assumed that the Arctic Oceanrepresents a barrier to climate changemovements of birds that are restricted to thenorthernmost coastline of Alaska. Therefore,11 species with the majority of theirbreeding population within the northern1/3 rd of the Arctic Coastal Plain wereassigned a score of “slightly increasedvulnerability” with regard to naturaldistribution barriers (Ruddy Turnstone, StiltSandpiper, Common Eider, SpectacledEider, White-rumped Sandpiper, PomarineJaeger, Buff-breasted Sandpiper, Steller’sEider, King Eider, Snow Goose, and Brant).Expert participants noted 30 specieswhose vulnerability might be increasedslightly by human responses to climatechange, using the list of adaptation ormitigation activities considered feasible forArctic Alaska during the next 50 years (seeMethods).18