Long‐term responses in arctic ungulate dynamics to changes in climatic and trophic processes

Abstract

Following predictions from climatic general circulation models, the effects of perturbations in global climate are expected to be most pronounced in the Northern Hemisphere. Elaborating on a recently developed plantherbivore-climate model, we explore statistically how different winter climate regimes and density-dependent processes during the past century have affected population dynamics of two arctic ungulate species. Our analyses were performed on the dynamics of six muskox and six caribou populations. In muskoxen, variation in winter climate, mediated through the North Atlantic Oscillation (NAO), explained up to 24% of the variation in interannual abundance, whereas in caribou up to 16% was explained by the NAO. Muskoxen responded negatively following warm and snowy winters, whereas caribou responded negatively to dry winters. Direct and delayed density dependence was recorded in most populations and explained up to 32% and 90% of variations in abundance of muskoxen and caribou, respectively.

Opposing plant community responses to warming with and without herbivores

“…The second, related concern is how population dynamics in both invertebrate and vertebrate populations will interact with future ecosystem and biome-scale changes associated with warming. Although insect damage and defoliation may become more frequent at northern latitudes with future warming (43,46,47), as evidence from the Paleocene-Eocene Thermal Maximum suggests (48), whether abundance of caribou and muskoxen will increase or decline as a result of climate change is far more difficult to predict (49,50). If the last two remaining large herbivores in this formerly megaherbivore-rich biome (51) were to expand or go extinct, however, it appears likely that plant community composition would undergo rapid and dramatic changes (52).…”

Capital and income breeding traits differentiate trophic match–mismatch dynamics in large herbivores

“…Previous studies have documented the critical relevance of density dependence in both Rangifer [36,[49][50][51] and muskoxen [50,52,53] population dynamics, so current and 1-year lagged calving season abundances were included as covariates during model construction. Seasonal herbivore abundance was calculated as the maximum number of individuals of each species seen on a single day at the study site throughout May-June.…”

Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch

“…Furthermore, dynamics of caribou and reindeer populations throughout the Northern Hemisphere respond to fluctuations in the North Atlantic Oscillation/Arctic Oscillation (Forchhammer et al 2002;Post 2005), and in some cases are entrained to the point of highly synchronous dynamics across distances of thousands of kilometres (Post & Forchhammer 2006). Such climateinduced synchrony represents a potentially adverse consequence of climate change because synchronously fluctuating populations face a greater risk of global extinction than do independently fluctuating populations (Palmquist & Lundberg 1998).…”