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ABSTRACT
Climate change can have a marked effect on the distribution and abundance of some species, as well as their interspecific interactions. In 1992, before ecological effects of anthropogenic climate change had developed into a topical research field, Hersteinsson and Macdonald published a seminal paper hypothesizing that the northern distribution limit of the red fox (Vulpes vulpes) is determined by food availability and ultimately climate, while the southern distribution limit of the Arctic fox (Vulpes lagopus) is determined by interspecific competition with the larger red fox. This hypothesis has inspired extensive research in several parts of the circumpolar distribution range of the Arctic fox. Over the past 25 years, it was shown that red foxes can exclude Arctic foxes from dens, space and food resources, and that red foxes kill and sometimes consume Arctic foxes. When the red fox increases to ecologically effective densities, it can cause Arctic fox decline, extirpation and range contraction, while conservation actions involving red fox culling can lead to Arctic fox recovery. Red fox advance in productive tundra, concurrent with Arctic fox retreat from this habitat, support the original hypothesis that climate warming will alter the geographical ranges of the species. However, recent studies show that anthropogenic subsidies also drive red fox advance, allowing red fox establishment north of its climate-imposed distribution limit. We conclude that synergies between anthropogenic subsidies and climate warming will speed up Arctic ecosystem change, allowing mobile species to establish and thrive in human-provided refugia, with potential spill-over effects in surrounding ecosystems.
KEYWORDS
Climate change; range shift; resource subsidy; mesopredator release; Vulpes lagopus; Vulpes vulpes
ABBREVIATIONS
BP: British Petroleum; IUCN: International Union for Conservation of Nature and Natural Resources
Introduction
The Earth's climate system is warming and there is high confidence that this has caused many species to shift their geographic ranges and local abundances (Parmesan & Yohe 2003; IPCC 2014). In the Arctic, the rate of warming has been higher than the global average, with increasing temperatures in particular from 1900 to the mid1940s and after the mid-1960s (McBean et al. 2005). Climate warming in the Arctic has, for example, prolonged the growing season for plants, changed the phenology, demography and dynamics of several species, and led to a northern advance of shrubs, trees...