Linking Alaska's Predicted Climate, Gyrfalcon, and Ptarmigan Distributions in Space and Time: A Unique 200-Year Perspective.

—Gyrfalcons (Falco rusticolus), rock Ptarmigan (Lagopus muta), and Willow Ptarmigan (L. lagopus) are quintessential Arctic species that are closely linked within the Arctic ecosystem. they likely face similar challenges in the face of rapid changes to their Arctic climate. Gyrfalcons in particular may be most challenged by rapid climate change because of their relatively specialized ecological niche, small population size, and K-selected life history strategy. Given this situation, we were interested in predicting how the distribution of these species may change under current climate predictions. therefore, we modeled the fundamental niche of each species in relation to temperature and precipitation in space and time across 200 years in Alaska (1900-2100). though the realized niche will ultimately determine where species are distributed in the future, we interpreted our predictions as representing the areas in which environmental conditions will allow the species to occur. We were interested in the large-scale, climate-induced trends in expansion, contraction, and overlap of these areas over time. We used the scenarios Network for Alaska Planning (sNAPs) regionalized/downscaled decadal mean June and December temperature and precipitation predictions from the A1b scenario, and as proposed by the United Nations Intergovernmental Panel on climate change (IPcc), to forward-model distributions from 2009-2099 in 30-year intervals. We used historical temperature and precipitation measurements from 1900-2006 to backwards-model the distribution of the species’ fundamental niche to qualitatively assess forward-modeling predictive accuracy. Forward-models predicted that the fundamental niches of Gyrfalcons and ptarmigan will contract spatially, and backwards-models suggested that they have contracted in the past as Alaska’s climate has warmed. Over the 200-year period, the total geographic area over which the species’ fundamental niches were predicted to occur decreased overall by 20% (Willow Ptarmigan), 40% (rock Ptarmigan) and 60% (Gyrfalcon). the distribution of the predicted fundamental niche of each species also became more fragmented, and the percent of spatial overlap between predicted presence of Gyrfalcons and ptarmigan declined over time. these alterations may affect the species’ long-term viability and co-evolution and will likely influence important biological processes such as dispersal, genetic diversity, predator-prey dynamics, and basic behavior. Predicted shifts in the geographic distribution of their fundamental niches may have cascading effects on other species, communities, and systems. For science-based, pro-active, adaptive management, ALAsKA’s NAtUrAL HIstOry was widely driven by the glacial retreat about 11,000 years ago. From then on, beringia spread and retreated to include what is today’s Alaska. Indigenous people affected the landscape (Glavin 2000), but a larger influence was post-contact with outside groups such as the russian colonization, the purchase of the Alaska territory by the United states in 1867, Alaska entering statehood in 1959, and industrial changes during the last 50 years. cumulative landscape modifications that have occurred since statehood are difficult to quantify or measure, but have had a significant effect in some respects, e.g. fragmentation, invasive species, and habitat loss (murphy et al. 2010). Despite Alaska’s reputation for being wild, the last frontier, and carrying endless and well-managed landscapes, it is clear that: a) truly pristine and untouched environments do not exist in times of man-made climate change (turner et al. 2002; chapin et al. 2009), b) Alaska is already dealing with major conservation challenges, including land cover and land use changes, development of natural resources, invasive species, and man-made climate change (symon et al. 2005, Hinzmann et al. 2005), c) climate change will affect Alaska to a greater extent than places of lower latitudes (martin et al. 2009), d) the Intergovernmental Panel on climate change (IPcc) scenarios of future climates have been demonstrated to underestimate rates of change in some systems (stroeve 2007), and e) the global population and Alaska’s urbanization is continuing to rise. the effects of these issues are found across the state and are affecting Gyrfalcons (Falco rusticolus), their prey, and their habitats. Biology of Gyrfalcons. —Gyrfalcons are apex predators that sit at the top of a food chain. therefore, changes in the food chain and habitats upon which this species depends are likely to be evident in these birds. this is especially so because the species breeds only in Arctic and sub-Arctic landscapes and relies heavily on a few prey species. Across Alaska and its circumpolar distribution, the Gyrfalcon is a ptarmigan specialist. Although it can take a diversity of prey species in several combinations and fractions, in nearly all instances ptarmigan makeup the majority of the diet, especially during pair bonding and egg production (booms et al. 2008). Hence, understanding and predicting how ptarmigan have and will adjust to landscape changes is integral to understanding, managing and predicting the response of Gyrfalcons. However, the Gyrfalcon’s reliance on ptarmigan does not necessitate that their spatial distributions and abundances are linear or automatic. buffer mechanisms and delays might exist that may blur the link and render it indirect, as documented in other systems (Watson 2010, Krebs et al. 2001). Biology of Ptarmigan. —Little is known about ptarmigan in Alaska’s landscape because the species has received little research or surveying effort in the state. the distribution and ecological niche of ptarmigan in Alaska and