Amanda M. Koltz

Rapid climate change in the Arctic is altering biological communities and their subsequent effects on ecosystem functioning. For example, warming‐induced shrub expansion accelerates biogeochemical cycles in part by increasing high‐quality litter inputs. Likewise, warming may enable higher densities of wolf spiders, which are dominant invertebrate predators whose activities indirectly alter plant litter decomposition rates. Although shrubs and wolf spiders are responding to climate change simultaneously, it is unclear how more shrub litter and more spiders together will influence elemental cycling in Arctic ecosystems. To test how warming could influence these processes, we used a fully factorial mesocosm experiment to quantify effects of wolf spiders on litter decomposition of an expanding species of dwarf deciduous shrub Betula nana under ambient and warmed conditions. We found higher densities of wolf spiders were consistently associated with more litter mass loss, and more C and N release regardless of warming treatment, indicating biotic interactions may be a stronger driver of short‐term B. nana litter decomposition than warming when wolf spiders are present. Our findings suggest the combined effects of warming‐induced shifts in plant and arthropod communities may further accelerate C and N cycling, which could cause positive feedbacks on Arctic shrub expansion.

Global change is causing major declines in biodiversity, especially of insects. Scientific interest in global change impacts on insects has increased in recent years, resulting in many different meta‐analyses examining questions within this topic. We performed a comprehensive review of meta‐analyses examining the effects of global change stressors on insects to identify well‐studied questions and gaps in our knowledge and synthesise the responses of insects to those stressors. We identified 75 meta‐analyses that fit our scope, accounting for 905 meta‐results and spanning 18 global change stressors. Our synthesis identified several global change stressors that are relatively well‐studied across insect groups, such as agriculture, habitat degradation, and pesticide use. Moreover, other global change stressors were found to be relatively less studied, highlighting areas that need more attention; for example, very few meta‐analyses considered the impacts of global warming, ozone, light pollution, and interactive effects of multiple stressors on insects. Most stressors are more associated with negative than positive effects on insects, except for nutrient addition, ozone, and air pollution. Negative effects accounted for the large majority of consequences on reproductive responses, which may help explain recent insect declines. Additionally, we found evidence for higher trophic levels being more negatively affected by global change and insects in aquatic habitats experiencing fewer negative responses to stressors. Given these largely negative impacts of global change on insects, we argue for the need for national and local policy actions to monitor and actively conserve insect communities.

Herbivores are an integral part of Arctic terrestrial ecosystems, driving ecosystem functioning and sustaining local livelihoods. In the context of accelerated climate warming and land use changes, understanding how herbivores contribute to the resilience of Arctic socio-ecological systems is essential to guide sound decision-making and mitigation strategies. While research on Arctic herbivory has a long tradition, recent literature syntheses highlight important geographical, taxonomic, and environmental knowledge gaps on the impacts of herbivores across the region. At the same time, climate change and limited resources impose an urgent need to prioritize research and management efforts. We conducted a horizon scan within the Arctic herbivory research community to identify emerging scientific and management priorities for the next decade. From 288 responses received from 85 participants in two online surveys and an in-person workshop, we identified 8 scientific and 8 management priorities centred on (a) understanding and integrating fundamental ecological processes across multiple scales from individual herbivore–plant interactions up to regional and decadal scale vegetation and animal population effects; (b) evaluating climate change feedbacks; and (c) developing new research methods. Our analysis provides a strategic framework for broad, inclusive, interdisciplinary collaborations to optimise terrestrial herbivory research and sustainable management practices in a rapidly changing Arctic.

Animal ecology and evolution are shaped by environmental perturbations, which are undergoing unprecedented alterations due to climate change. Fire is one such perturbation that causes significant disruption by causing mortality and altering habitats and resources for animals. Fire regimes are changing on a global scale, but the effects of these changes on animal communities are poorly understood. Arthropods are one of the most ubiquitous and diverse animal taxa on the planet and their populations are sensitive to environmental change. Given their wide‐ranging impacts on ecosystem functioning, a better understanding of arthropod responses to changing fire regimes is critical and may also provide more general insights into how other groups might respond to fire. Here, we provide a comprehensive meta‐analytical assessment of how fire influences the arthropod community across habitats and functional groups. Using data from 130 peer‐reviewed papers across the globe, we tested how a variety of fire characteristics, including management regime, severity and time‐since‐fire affect arthropod populations and communities across habitats. Our results show that arthropod communities display substantial variation in response to fire and that community‐level responses are most likely to be detected within the first year. Responses also vary depending on fire characteristics and habitat. Specifically, while community metrics such as diversity were increased by low severity fires, they were reduced by high severity fires. Likewise, evenness increased after prescribed burns but was reduced after wildfire. Measures of arthropod community structure decreased following fires in deserts and forests. Across the entire arthropod community, fire also had variable effects on community diversity. Fire tended to have a negative effect size on arthropods across life stages, but responses did vary among groups. Nearly all functional groups exhibited a negative response to fire with the exception of herbivores, for which abundance, diversity and richness increased after fire. Our results suggest that the increasing prevalence of high‐severity wildfires are changing the structure of arthropod communities. Given their ubiquitous presence and diverse roles in terrestrial ecosystems, these community changes are likely to affect ecosystem functioning in various ways, including through increased herbivory. Read the free Plain Language Summary for this article on the Journal blog.

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.