A boreal invasion in response to climate change? Range shifts and community effects in the borderland between forest and tundra

Abstract

It has been hypothesized that climate warming will allow southern species to advance north and invade northern ecosystems. We review the changes in the Swedish mammal and bird community in boreal forest and alpine tundra since the nineteenth century, as well as suggested drivers of change. Observed changes include (1) range expansion and increased abundance in southern birds, ungulates, and carnivores; (2) range contraction and decline in northern birds and carnivores; and (3) abundance decline or periodically disrupted dynamics in cyclic populations of small and medium-sized mammals and birds. The first warm spell, 1930–1960, stands out as a period of substantial faunal change. However, in addition to climate warming, suggested drivers of change include land use and other anthropogenic factors. We hypothesize all these drivers interacted, primarily favoring southern generalists. Future research should aim to distinguish between effects of climate and land-use change in boreal and tundra ecosystems.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-014-0606-8) contains supplementary material, which is available to authorized users.

Red foxes colonizing the tundra: genetic analysis as a tool for population management

“…The ongoing climate change is forecasted to reduce and fragment mountain tundra habitats and induce alterations in the ecological function and dynamics (Guisan et al 2014;Elmhagen et al 2015). One consequence of the milder climate is that boreal species expand from southern sources and establish in northern habitats, a process that by many means is comparable to that of invasive species taking over novel habitats.…”

“…One consequence of the milder climate is that boreal species expand from southern sources and establish in northern habitats, a process that by many means is comparable to that of invasive species taking over novel habitats. There are two, not mutually exclusive processes, underlying this process (Elmhagen et al 2015). In southern areas, warmer temperatures and increased land use induce demographic growth that in combination with range expansion will increase the distribution and abundance of boreal species.…”

“…In southern areas, warmer temperatures and increased land use induce demographic growth that in combination with range expansion will increase the distribution and abundance of boreal species. Meanwhile, the opposite occurs in northern habitats, where reductions in habitat availability cause population declines and/or range contractions of populations living under sub-Arctic conditions (Elmhagen et al 2015). These declines can be further accelerated by boreal species advancing into tundra regions and change ecosystem dynamics by competition or predation (Ims and Fuglei 2005), or by introducing novel diseases and parasites (e.g.…”

“…Kutz et al 2005). There is thus a prevalent need to devote research focus towards the boreal expansion process to implement efficient and ethical management strategies as well as for conservation of threatened native species (Elmhagen et al 2015).…”

“…Furthermore, the decision to disperse and establish in a novel habitat may be further influenced by sex-specific dispersal patterns and/or social factors (Lawson-Handley and Perrin 2007). A preference for establishing in territories adjacent to close relatives, or synchronize dispersal with close relatives have been documented in a closely related species (Ehrich et al 2012;Elmhagen et al 2015). It is however not known how these factors influence to the ongoing red fox invasion of the Fennoscandian tundra, but it is possible that there may be a higher occurrence of close relatives in the expansion front.…”