Herbivores in Arctic ecosystems: Effects of climate change and implications for carbon and nutrient cycling

Abstract

Arctic terrestrial herbivores influence tundra carbon and nutrient dynamics through their consumption of resources, waste production, and habitat‐modifying behaviors. The strength of these effects is likely to change spatially and temporally as climate change drives shifts in herbivore abundance, distribution, and activity timing. Here, we review how herbivores influence tundra carbon and nutrient dynamics through their consumptive and nonconsumptive effects. We also present evidence for herbivore responses to climate change and discuss how these responses may alter the spatial and temporal distribution of herbivore impacts. Several current knowledge gaps limit our understanding of the changing functional roles of herbivores; these include limited characterization of the spatial and temporal variability in herbivore impacts and of how herbivore activities influence the cycling of elements beyond carbon. We conclude by highlighting approaches that will promote better understanding of herbivore effects on tundra ecosystems, including their integration into existing biogeochemical models, new applications of remote sensing techniques, and the continued use of distributed experiments.

Metabarcoding of fecal pellets in wild muskox populations reveals negative relationships between microbiome and diet alpha diversity

“…Arctic warming not only affects Arctic plant species diversity but the phenology of local vegetation. Availability and reliability of vegetation play a role in muskox demographics with earlier green‐up times associated with increased population sizes and plant consumption (Eikelenboom et al, 2021 ; Koltz et al, 2022 ; Post et al, 2019 ). Muskoxen are capital breeders and are expected to be relatively insensitive to changing plant phenology as their breeding is reliant on their body reserves from the past year, rather than resources obtained during the breeding period (Gustine et al, 2010 ; Kerby & Post, 2013 ).…”

“…Arctic warming not only affects Arctic plant species diversity but the phenology of local vegetation. Availability and reliability of vegetation play a role in muskox demographics with earlier green-up times associated with increased population sizes and plant consumption (Eikelenboom et al, 2021;Koltz et al, 2022;Post et al, 2019).…”

Long‐term herbivore removal experiments reveal how geese and reindeer shape vegetation and ecosystem CO2‐fluxes in high‐Arctic tundra

“…This likely reflects inherent differences in both habitat sensitivity and habitat use, as well as herbivores' characteristics and grazing pressure. As recently argued by Koltz et al (2022), addressing the role of herbivores in the habitat in which they operate can help us understand how herbivory influences ecosystem structure and function across the heterogeneous tundra landscape. This, in turn, will provide important information to project the effects of shifting herbivore population densities on ecosystem functioning, and refine predictions on whether and where these shifts are likely to mitigate or further amplify the impact of climate change on Arctic ecosystems.…”

“…In the latter, partly due to a mixture of anthropogenic factors, densities of herbivore populations are undergoing drastic changes (Fox & Madsen, 2017; Uboni et al, 2016). With the Arctic experiencing the fastest rate of climate warming on Earth (IPCC, 2021), together with the potential for herbivory to modulate warming effects on vegetation and ecosystem processes (Leffler et al, 2019; Post & Pedersen, 2008; Sjögersten et al, 2008), interest in how herbivores affect tundra ecosystems is high (Barrio et al, 2016; Koltz et al, 2022). A growing body of studies has shown that herbivore impacts are far from homogeneous and often depend on both the species and the ecological context (Bernes et al, 2015; Lara et al, 2017; Petit Bon, Inga, et al, 2020; Sjögersten et al, 2008; Speed et al, 2010; Sundqvist et al, 2019).…”

“…However, due to the paucity of long-term removal experiments in the Arctic, and even more so in the high Arctic (Forbes et al, 2019), studies on how herbivores influence ecosystem structure and function across the tundra landscape are scarce. With the Arctic rapidly changing, there is an urgent need for experiments testing the role of different herbivores in shaping tundra ecosystems (Koltz et al, 2022).…”