Trophic dynamic of terrestrial Arctic ecosystems under anthropogenic pressure

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The identification of mechanisms that determine the dynamics of food webs is a key research area in ecology; it also represents a major step towards an improved understanding of the functioning and the vulnerability of ecosystems. However, those mechanisms cannot be understood without considering two major contemporary human-induced perturbations, namely climate change and human activities. Nowhere else on earth are the effects of global warming more threatening than in the Arctic, yet development and human presence is booming in this largely untouched biome. To fully understand how dynamics of food webs are affected by human-induced perturbations, it is also essential to consider that most ecosystems possess the capacity for energy exchanges with other ecosystems, e.g. food inputs resulting from human activities. A clear understanding of the roles of energy exchanges in food web dynamics is a prerequisite when assessing the extent of effects of global changes on tundra ecosystems experiencing a simultaneous decline of their key herbivores (e.g. lemmings) along with an increasing presence of alien predators (e.g. red foxes) that have the potential to support their energy needs from anthropogenic food sources. Such an ongoing transformation of tundra ecosystems raises major questions with respect to the fate of arctic predators and arctic-nesting birds, and to the overall functioning of arctic food webs subject to global disturbances. One of the greatest uncertainties in forecasting the direct and indirect effects of global environmental change on ecosystems is related to understanding how it will affect species interactions (here predator-prey interactions). The long-term objective of my research program is to investigate the role of predator-prey interactions in the dynamics of terrestrial Arctic food webs to better understand their functioning and sensitivity to anthropogenic perturbations, such as climate change and human-induced food subsidies. The proposed program will be conducted in two study systems (snow goose-arctic fox interaction and arctic predators-subsidies interactions) and addresses two short-term objectives: 1) to investigate the role of predator-prey interactions in mediating climatic impacts on arctic-nesting birds and arctic predators; and 2) to study the influence of climate and human presence on the rate and direction of changes in population dynamics and resource use of arctic top-predators. To achieve these objectives, I intend to use existing large-scale datasets on Arctic terrestrial vertebrates (geese and arctic top-predators, in particular) and to develop new field-based data acquisition strategies in the Canadian Arctic aiming at generating long-term research to monitor the survival and breeding success in key arctic species and to experimentally manipulate a key driving force in the terrestrial tundra, i.e. predation risk. My approaches will encompass capture-mark-recapture, stable isotopes, time series and path analyses, together with the regular consultation of local experts in Inuit communities. The program is both integrative and innovative. First, the work integrates trophic interactions under direct and indirect human perturbation in a single framework, strengthening our understanding of the population dynamics of migratory birds and their predators. Second, the approach uses state-of-the-art analytical and monitoring tools on wildlife species at the heart of Arctic communities' traditional life. While training several HQP and northerners in Arctic science, the scientific knowledge gained from this research program will provide a solid base for sound policy and wildlife management programs in the Arctic.