Cascading effects of climate change in a rapidly warming high Arctic ecosystem

One priority in climate research is to predict climate change effects beyond the species level. However, accounting for trophic interactions between species (indirect climate effects), density-dependence and demography (age-structure fluctuations) often proves difficult even in population-dynamical analyses of single species. At the community level, these challenges are particularly hard to address because they require mechanistic insights into both species-specific and shared climatic signals acting across species. These insights must be integrated in sound demographic models based on long-term, high-quality data. In CASCADE I address this with a case study from high Arctic Svalbard, characterized by a simple trophic structure, strong warming, and unique availability of high-quality data. The study will demonstrate how a shift from the single-species perspective to a multi-species modelling framework for community-level dynamics may significantly alter our predictive understanding of climate effects. First, I will perform state-of-the art demographic modelling of barnacle geese, a key herbivore which is protected nationally and internationally. Almost three decades of mark-recapture data are available from my host institution (Univ. Groningen, NL). A long-term research stay there will enable me to prepare data, estimate annual age-specific vital rates and population sizes, and disentangle the effects of environmental stochasticity (climate) from density-dependence and age structure fluctuations through careful demographic modelling. Finally, I will test the hypothesis that due to trophic interactions, effects of winter climate change and extreme events on the overwintering vertebrates cascade to the migratory geese and beyond. Because of the spatial scales and species involved, the results will have large management implications reaching from Svalbard to the continental wintering grounds of migratory birds.