The vast boreal biome plays an important role in the global carbon cycle but is experiencing particularly rapid climate warming, threatening the integrity of valued ecosystems and their component species. We developed a framework and taxonomy to identify climate‐change refugia potential in the North American boreal region, summarizing current knowledge regarding mechanisms, geographic distribution, and landscape indicators. While “terrain‐mediated” refugia will mostly be limited to coastal and mountain regions, the ecological inertia (resistance to external fluctuations) contained in some boreal ecosystems may provide more extensive buffering against climate change, resulting in “ecosystem‐protected” refugia. A notable example is boreal peatlands, which can retain high surface soil moisture and water tables even in the face of drought. Refugia from wildfire are also especially important in the boreal region, which is characterized by active disturbance regimes. Our framework will help identify areas of high refugia potential, and inform ecosystem management and conservation planning in light of climate change.
Identifying and understanding why traits make species vulnerable to changing climatic conditions remain central problems in evolutionary and applied ecology. We used spring snow cover duration as a proxy for phenological timing of wetland ecosystems, and examined how snow cover duration during spring and during the entire snow season affected population dynamics of duck species breeding in the western boreal forest of North America, 1973America, -2007 We predicted that population level responses would differ among duck species, such that late-nesting species with reduced flexibility in their timing of breeding, i.e. scaup (Aythya spp.) and scoter (Melanitta spp.), would be more strongly affected by changing snow cover conditions relative to species better able to adjust timing of breeding to seasonal phenology, i.e. mallard (Anas platyrhynchos) and American wigeon (Anas americana). Population growth rates of scaup and scoter were positively linked to spring snow cover duration; after accounting for effects of density dependence, larger populations resulted after springs with long snow cover duration than after springs with short snow cover duration. In contrast, population growth rates of mallard and wigeon were either negatively or only weakly associated with snow cover duration. Duck population models were then incorporated with snow cover duration derived from climate model simulations under the A2 emission scenario, and these predictions suggested that latenesting duck species will experience the most severe population declines. Results are consistent with a hypothesis that the gradual climatic warming observed in the western boreal forest of North America has contributed to and may continue to exacerbate population declines of scaup and scoter.
We studied harvest of Ross's geese in North America by examining recoveries from 30,774 Ross's geese marked from 1989 to 2001 in Queen Maud Gulf Migratory Bird Sanctuary (QMGMBS), Nunavut, in Canada's central arctic. Recoveries reported by hunters in North America provided information about timing and location of harvest for 2,152 birds. Banded Ross's geese were shot and reported mostly from the U.S. (68%) and Canada (30%), but also Mexico (2%) during the study. From 1989 to 2001, there have been eastward shifts in distribution of recoveries from the Pacific Flyway to the midcontinent in the U.S., and from Alberta to Saskatchewan in Canada. Harvest in Canada was concentrated in southern Saskatchewan (85%), whereas U.S. distribution of recoveries was much broader with most recoveries from the Pacific (49%), Central (39%), and Mississippi (12%) Flyways. Continental harvest of Ross's geese began to increase in 1994 concurrent with liberalization of hunting regulations in the Canadian Prairie provinces and the Central and Mississippi Flyways, and the increased propensity of U.S. hunters, who now account for 90% of the continental harvest, to hunt outside of the U.S. Harvest from further liberalization of hunting regulations for light geese as part of the U.S. conservation order has accounted for ≤15% of continental harvest annually since 1998. Nevertheless, increased harvest of Ross's geese from the 1989 hunting season (∼8,000 birds) to the 2001 season (∼90,000 birds) best accounted for annual variation in adult survival, but was unrelated to juvenile survival. Survival of adults was >0.91 before 1994 but declined to ∼0.80 by 1998–2000 hunting seasons. Juvenile survival was relatively stable among years and ranged from 0.33 to 0.41. We found that mortality probability of adults marked with neckbands was 1.94 to 2.62 times higher than for adults without neckbands, but only 1.08 to 1.13 times higher in respective groups of juvenile Ross's geese. Thus, we advise against use of neckbands for estimation of survival in Ross's geese. The similarity and mixing of Ross's geese with snow geese in western and central North America are impediments to separate harvest management of each species. However, geographical adjustment of harvest regulations for Ross's geese in Canada is advised, with the dual objective of reducing midcontinent snow geese while conserving populations of Ross's geese on traditional winter areas in the Pacific Flyway. We recommend Ross's geese continue to be marked with legbands in QMGMBS, their principal breeding range, at least as long as liberal harvest regulations remain in place for reduction of midcontinent snow geese.
populations était aussi très sensible aux variations unitaires ou proportionnelles du succès d'éclosion moyen et des taux de survie des canetons ou des juvéniles. Étant donné les faibles effectifs d'échantillons disponibles pour certains aspects-clé du cycle de vie du Petit Fuligule, nous recommandons que des travaux additionnels soient effectués sur les taux vitaux qui ont une influence majeure sur l'accroissement des populations et leur effectif (ex. taux de survie des adultes). Nos modèles de cycle de vie devraient être testés et mis à jour régulièrement afin de guider l'étude et la gestion des populations de Petit Fuligule dans un contexte adaptatif.
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