Global change impacts a threatened species through alteration of predator-prey dynamics

Although global change can reshape ecosystems by triggering cascading effects on food webs, indirect interactions remain largely overlooked. Climate- and land use-induced changes on landscape cause shifts in vegetation composition, which affect entire food webs. We used simulations of forest dynamics and movements of interacting species, parameterized by empirical observations, to predict the outcomes of global change on a large-mammal food-web in boreal forest. We demonstrate that climate- and land use-induced changes of forest landscapes exacerbate asymmetrical apparent competition between moose and threatened caribou populations, through wolf predation. While increased prey mortalities came from both behavioural and numerical responses, indirect effects from numerical responses had an overwhelming effect. The increase in caribou mortalities was exacerbated by the cumulating effects of land-use over the short term and climate change impacts over the long-term, with higher impact of land-use. Indirect trophic interactions will be key to understanding community dynamics under global change.