Location of studies and evidence of effects of herbivory on Arctic vegetation: a systematic map
Herbivores modify the structure and function of tundra ecosystems. Understanding their impacts is necessary to assess the responses of these ecosystems to ongoing environmental changes. However, the effects of herbivores on plants and ecosystem structure and function vary across the Arctic. Strong spatial variation in herbivore effects implies that the results of individual studies on herbivory depend on local conditions, i.e., their ecological context. An important first step in assessing whether generalizable conclusions can be produced is to identify the existing studies and assess how well they cover the underlying environmental conditions across the Arctic. This systematic map aims to identify the ecological contexts in which herbivore impacts on vegetation have been studied in the Arctic. Specifically, the primary question of the systematic map was: “What evidence exists on the effects of herbivores on Arctic vegetation?”.
We used a published systematic map protocol to identify studies addressing the effects of herbivores on Arctic vegetation. We conducted searches for relevant literature in online databases, search engines and specialist websites. Literature was screened to identify eligible studies, defined as reporting primary data on herbivore impacts on Arctic plants and plant communities. We extracted information on variables that describe the ecological context of the studies, from the studies themselves and from geospatial data. We synthesized the findings narratively and created a Shiny App where the coded data are searchable and variables can be visually explored.
We identified 309 relevant articles with 662 studies (representing different ecological contexts or datasets within the same article). These studies addressed vertebrate herbivory seven times more often than invertebrate herbivory. Geographically, the largest cluster of studies was in Northern Fennoscandia. Warmer and wetter parts of the Arctic had the largest representation, as did coastal areas and areas where the increase in temperature has been moderate. In contrast, studies spanned the full range of ecological context variables describing Arctic vertebrate herbivore diversity and human population density and impact.
The current evidence base might not be sufficient to understand the effects of herbivores on Arctic vegetation throughout the region, as we identified clear biases in the distribution of herbivore studies in the Arctic and a limited evidence base on invertebrate herbivory. In particular, the overrepresentation of studies in areas with moderate increases in temperature prevents robust generalizations about the effects of herbivores under different climatic scenarios.
Browsing, Grazing, Grubbing, Defoliation, Tundra, Invertebrate, Vertebrate, Forest-tundra, Plant–herbivore interaction
Along with climate change, herbivory is considered a main driver of ecosystem change in terrestrial Arctic environments. Understanding how herbivory influences the resilience of Arctic ecosystems to ongoing environmental changes is essential to inform policy and guide sustainable management practices. However, many studies indicate that the effects of herbivores on plants and ecosystem functioning depend on the abiotic and biotic conditions where the interaction takes place, i.e. the ecological context. Yet, the range of ecological contexts in which herbivory has been studied in the Arctic has not been systematically assessed. A lack of such evaluation prevents understanding the robustness and generalizability of our knowledge of Arctic herbivore effects on vegetation and ecosystems. The main objective of our systematic map is to identify the ecological contexts where herbivory is studied in the Arctic. Hence, this systematic map will enable us to assess our ability to make generalizable and robust conclusions regarding the impacts of Arctic herbivory.
We will search academic and grey literature using databases, search engines and specialist websites, and select studies addressing the response of the plant(s) to herbivory, deemed relevant in terms of (i) population (terrestrial Arctic plants and plant communities), (ii) exposure (herbivory, including disturbance and fertilization effects of herbivores), and (iii) modifier (ecological context being in the terrestrial Arctic including forest-tundra). We will synthesize the results using systematic mapping approaches.