Reindeer turning maritime: Ice‐locked tundra triggers changes in dietary niche utilization

Abstract

The rapid warming of the Arctic may not only alter species’ abundances and distributions, but likely also the trophic interactions within and between ecosystems. On the high‐arctic tundra, extreme warm spells and associated rain‐on‐snow events in winter can encapsulate the vegetation entirely in ground‐ice (i.e., basal ice) and directly or indirectly affect plants, herbivores, and carnivores. However, the implications of such extreme events for trophic interactions and food‐web ecology are generally far from understood. Here, we show that wild Svalbard reindeer populations increasingly isolated by lack of sea‐ice respond to rain‐on‐snow and ice‐locked pastures by increased kelp consumption. Based on annual population surveys in late winters 2006–2015, the proportion of individual reindeer feeding along the shoreline increased the icier the winter. Stable isotope values (δ34S, δ13C, δ15N) of plants, washed‐ashore kelp, and fresh reindeer feces collected along coast‐inland gradients, confirmed ingestion of marine biomass by the reindeer in the shoreline habitat. Thus, even on remote islands and peninsulas increasingly isolated by sea‐ice loss, effects of climate change may be buffered in part by behavioral plasticity and increased use of resource subsidies. This marine dimension of a terrestrial herbivore's realized foraging niche adds to evidence that global warming significantly alters trophic interactions as well as meta‐ecosystem processes.

Location of studies and evidence of effects of herbivory on Arctic vegetation: a systematic map

“…The effects of herbivores on plants are thus expected to differ along climatic gradients within the Arctic [18]. Distance to the coast can matter due to marine subsidies to the food web [19] or salinity [20,21] and distance to the treeline due to spillover of boreal herbivores [22][23][24]. The magnitude of recent warming and the composition of herbivore communities are also important [25,26].…”

Subarctic catchment water storage and carbon cycling – Leading the way for future studies using integrated datasets at Pallas, Finland

“…Changes in the Arctic water cycle reflect complex interactions in Arctic landscapes, processes, and ecosystems. Examples include retreating seasonal snow cover, increasing temperatures and precipitation, and shifts in precipitation from snow to rainfall (Bring et al, 2016; Hansen et al, 2019; Krasting et al, 2013; Pulliainen et al, 2020). Seasonal soil frost and permafrost conditions are predicted to change substantially (Aalto et al, 2018; Ala‐Aho et al, 2021a, 2021b; Biskaborn et al, 2019; Wang et al, 2019), modifying hydrological pathways and biogeochemical processes (Czimczik & Welker, 2010; Lupascu et al, 2018; Nowinski et al, 2010; Serikova et al, 2018) and causing infrastructure failure (Hjort et al, 2018).…”

Identifying seaweed consumption by sheep using isotope analysis of their bones and teeth: Modern reference δ13C and δ15N values and their archaeological implications

“…Therefore, while consumption of seaweed may cause elevated δ 15 Ncollagen values if alternative food sources have substantially lower δ 15 N values (e.g. in Hansen et al, 2019), this is not always the case, and it should not be assumed that seaweed consumption automatically causes elevated δ 15 Ncollagen. Likewise, elevated δ 15 Ncollagen values are not diagnostic of the consumption of seaweed.…”