A cosmogenic nuclide chronology of Cordilleran Ice Sheet configuration during the Last Glacial Maximum in the northern Alexander Archipelago, Alaska

The late-Pleistocene history of the coastal Cordilleran Ice Sheet (CIS) remains relatively unstudied compared to chronologies of the Laurentide Ice Sheet. Yet accurate reconstructions of CIS extent and timing of ice retreat along the Pacific Coast are essential for a variety of reasons including paleoclimate modeling, assessing meltwater contribution to the North Pacific, and determining the availability of ice-free land along the coastal CIS margin for human migration from Beringia into the Americas. To improve the chronology of CIS history in the Alexander Archipelago, Alaska, we applied 10Be and 36Cl dating to boulders and glacially sculpted bedrock outcrops in areas previously hypothesized to have remained ice-free throughout the local Last Glacial Maximum (lLGM; 20–17 ka). Results indicate that these sites, and more generally the coastal northern Alexander Archipelago, became ice-free by 15.1 ± 0.9 ka (n = 12 boulders; 1 SD). We also provide further age constraints on deglaciation along the southern Alexander Archipelago and combine our new ages with data from two previous studies. We determine that ice retreated from the outer coast of the southern Alexander Archipelago at 16.3 ± 0.8 ka (n = 14 boulders; 1 SD). These results collectively indicate that areas above modern sea level that were previously mapped as glacial refugia were covered by ice during the lLGM until between ~16.3 and 15.1 ka. As no evidence was found for ice-free land during the lLGM, our results suggest that previous ice-sheet reconstructions underestimate the regional maximum CIS extent, and that all ice likely terminated on the continental shelf. Future work should investigate whether presently submerged areas of the continental shelf were ice-free.

Future population trends and drivers of change for Alexander Archipelago wolves on and near Prince of Wales Island, Alaska

Background. The Alexander Archipelago wolf, inhabiting the coastal temperate rainforest of North America, was recently evaluated for protection under the U.S. Endangered Species Act, but ultimately was not listed. Stressors thought to be impacting the population include about habitat alteration from industrial timber harvest and subsequent declines in prey (deer), increased human-caused mortality, and climate change. Methods. To evaluate how these factors likely will affect future abundance of wolves and deer, we constructed a model linking wolf and deer population dynamics to environmental conditions and management regulations. We restricted our model to Prince of Wales and outlying islands, because this area is partially isolated, is the focus of timber harvest in the region, and has the most empirical data available for model parameterization. We examined 6 combinations of future timber harvest, winter severity, wolf harvest regulations, and roads on population dynamics of deer and wolves, developed by a panel of experts. Results. Outcomes across scenarios after 30 years varied, with changes in wolf abundance ranging from a 156% increase to a 41% decline, whereas deer abundance declined from 10−37% after 30 years. Mean percentage of the 31 pack areas that were vacant after 30 years ranged from 0 to 67%, indicating that environmental conditions strongly affected pack success. Variation in wolf abundance was driven primarily by changes in wolf harvest regulations, with smaller contributions from road density, forest succession, and severe-winter frequency. Given current low estimated wolf numbers and continued legal and illegal harvest, this raises conservation concerns for the future of wolves in our study area. In addition, we found that wolf declines could be greater if wolves rely more heavily on deer in the future, for instance if salmon availability declines under future climate change, but also that reduction of deer hunting could increase wolf abundance. Discussion. The potential importance of illegal harvest in wolf population dynamics needs further acknowledgement and treatment. However, changes to harvest regulations, which would not reduce unreported harvest, could still be a powerful tool for management of this small, declining, and insular population. Nevertheless, maximum abundance of wolves appears to be curtailed by the steady decline in carrying capacity forecast across all timber management plans currently under consideration. Although we evaluated factors affecting wolf abundance individually, we encourage a holistic approach to management of this predator-prey system in an altered ecosystem.

Future population trends and drivers of change for Alexander Archipelago wolves on and near Prince of Wales Island, Alaska

Background. The Alexander Archipelago wolf, inhabiting the coastal temperate rainforest of North America, was recently evaluated for protection under the U.S. Endangered Species Act, but ultimately was not listed. Stressors thought to be impacting the population include about habitat alteration from industrial timber harvest and subsequent declines in prey (deer), increased human-caused mortality, and climate change. Methods. To evaluate how these factors likely will affect future abundance of wolves and deer, we constructed a model linking wolf and deer population dynamics to environmental conditions and management regulations. We restricted our model to Prince of Wales and outlying islands, because this area is partially isolated, is the focus of timber harvest in the region, and has the most empirical data available for model parameterization. We examined 6 combinations of future timber harvest, winter severity, wolf harvest regulations, and roads on population dynamics of deer and wolves, developed by a panel of experts. Results. Outcomes across scenarios after 30 years varied, with changes in wolf abundance ranging from a 156% increase to a 41% decline, whereas deer abundance declined from 10−37% after 30 years. Mean percentage of the 31 pack areas that were vacant after 30 years ranged from 0 to 67%, indicating that environmental conditions strongly affected pack success. Variation in wolf abundance was driven primarily by changes in wolf harvest regulations, with smaller contributions from road density, forest succession, and severe-winter frequency. Given current low estimated wolf numbers and continued legal and illegal harvest, this raises conservation concerns for the future of wolves in our study area. In addition, we found that wolf declines could be greater if wolves rely more heavily on deer in the future, for instance if salmon availability declines under future climate change, but also that reduction of deer hunting could increase wolf abundance. Discussion. The potential importance of illegal harvest in wolf population dynamics needs further acknowledgement and treatment. However, changes to harvest regulations, which would not reduce unreported harvest, could still be a powerful tool for management of this small, declining, and insular population. Nevertheless, maximum abundance of wolves appears to be curtailed by the steady decline in carrying capacity forecast across all timber management plans currently under consideration. Although we evaluated factors affecting wolf abundance individually, we encourage a holistic approach to management of this predator-prey system in an altered ecosystem.

Possible refugia in the Alexander Archipelago of southeastern Alaska during the late Wisconsin glaciation

The interpretation of the extent of late Wisconsin glaciation in southeastern Alaska has varied between geologists and biologists. Maps and reports of the region prepared by geologists commonly indicated that late Wisconsin ice extended as a large uniform front west to the edge of the continental shelf. However, the distribution of plants and animals in the region has led many biologists to suggest that there may have been ice-free areas that served as refugia during the late Wisconsin. Based on analyses of aerial photographs, topographic maps, and bathymetric charts, in conjunction with a review of previous literature and reconnaissance fieldwork throughout the region, this study presents data supporting a limited ice extent in the Alexander Archipelago during the late Wisconsin and identifies possible ice-free areas that may have served as refugia. These areas include (1) the Fairweather Ground, (2) the Herbert Graves Island area, (3) the western coast of southern Baranof Island and adjacent continental shelf, (4) Coronation Island and the adjacent continental shelf, (5) the Warren Island area, (6) the continental shelf from west of Heceta Island to Forrester Island in the south, (7) parts of the west coast of southern Dall Island, and (8) lowland areas in southern Prince of Wales Island. The identification of these possible refugia has bearing on the recolonization of the Alexander Archipelago, as they could have served as centers of biotic dispersal upon regional deglaciation and as stepping stones for early humans with a maritime tradition entering the western hemisphere from Asia.