Water Birds on the Edge: first circumpolar assessment of climate chage impact of Arctic breeding water birds. WCMC Biodiversity Series 11

The purpose of this study is to investigate the potential impacts of climate change on a number of water bird species breeding in the Arctic.The study applies the HadCM2GSal general circulation model (GCM) of the Hadley Centre to assess the direct impacts of a changing climate on the breeding conditions of five selected Arctic water bird populations.Additionally, the current distribution of 25 species is compared with changes in vegetation predicted by two climate scenarios, a moderate one based on rise in temperature of only 1.7C (HadCM2GSal) and an extreme scenario with a rise of 5C (UKMO) at the time of C0 2 doubling (2070-2099).Analysis of spring and summer data of temperature and precipitation over the last 50 years, interpolated over the area of the species' currently known distribution, demonstrate a significant correlation between the mean June temperature and the juvenile percentage as a measure of breeding success in the Arctic in both of the tested populations of the White-fronted Goose (Anser albifrons) and in the Taimyr population of the Knot (Calidris c. canutus).The Nearctic population of the Knot (C.c. islandica), as well as the Curlew Sandpiper (Calidris ferruginea) breeding on the Taimyr Peninsula, do not show a correlation with the mean June temperature.Under the HadCM2GSal model, an increase of 1% C0 2 /yr results in a moderate increase of the mean June temperature in the Taimyr-breeding area of the White-fronted Goose.The conditions for the Taimyr population are particularly favourable for the period around 2020.According to the scenario, the temperature falls again by 2050 but never below the average of the last 30 years.However, a considerable cooling of the breeding grounds of the goose population in West Greenland could lead to a drop in size of the fragile population, which winters only in the western part of the British Isles.According to the climate model, the temperature around 2080 would not be above the mean values of today.For the three wader populations that were tested, the pattern of response towards certain climate variables is not consistent, and for these species, the projection of the mean June temperature or other climate variables into a future scenario was not performed.More species need to be tested to ensure the inclusion of the right variables into future scenarios.Despite these uncertainties, the study maintains that all Arctic water bird populations breeding in the predicted area of cooler spring and summer temperatures, between Northeastern Canada and West Greenland, remain of special concern.Most of them, including the Nearctic Knot and the Sanderling {Calidris alba) winter regularly in British coastal waters.The results of the vegetation models show a large variation in the impact of predicted changes in vegetation on the 25 species.According to the moderate HadCM2GSal model, 76% of Tundra Bean Geese (Anser fabalis rossicus/serrirostris) will be affected by the alteration of tundra habitats, whilst only 5% of the Sanderling will be affected.For two of the three water bird species which are considered globally threatened, namely the Red-breasted Goose (Branta rufwollis) and the Spoonbilled Sandpiper (Eurynorhynchus pygmaeus), 67% and 57% of their current breeding range will change from tundra to forest, respectively.The values for the extreme UKMO scenario are even higher, reaching 85% for the Red-breasted Goose.This additional loss of habitat will place these two species at a higher risk of extinction.The Emperor Goose (Anser canagicus), already in decline and with 54% of its small range affected, is highlighted as needing further conservation attention.The results from this study require careful interpretation.Although in Alaska there is already evidence of an increase in forest area, and with pollen analyses from the Holocene indicating that vast shifts in forest areas occurred during interglacial periods, scientists still argue about the likelihood of such scenarios and about the rate, speed and scale of forest growth into the tundra.However, the results of this study reflect an important component in a matrix of factors affecting the future development of Arctic-breeding water birds.They have to be interpreted in relation to other factors affecting the populations of these birds, such as natural predation, hunting (mainly outside the Arctic) and the m effects of climate change (in particular sea-level rise) outside the Arctic.Further research will be earned out to refine the existing results, based on improved and updated data on distribution and refined GCMs.Other important components such as sea level rise and change in river runoff in the Arctic and on the major staging areas during migration will be taken into account.

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