Abstract

Extreme climate events often cause population crashes but are difficult to account for in population-dynamic studies. Especially in long-lived animals, density dependence and demography may induce lagged impacts of perturbations on population growth. In Arctic ungulates, extreme rain-on-snow and ice-locked pastures have led to severe population crashes, indicating that increasingly frequent rain-on-snow events could destabilize populations. Here, using empirically parameterized, stochastic population models for High-Arctic wild reindeer, we show that more frequent rain-on-snow events actually reduce extinction risk and stabilize population dynamics due to interactions with age structure and density dependence. Extreme rain-on-snow events mainly suppress vital rates of vulnerable ages at high population densities, resulting in a crash and a new population state with resilient ages and reduced population sensitivity to subsequent icy winters. Thus, observed responses to single extreme events are poor predictors of population dynamics and persistence because internal density-dependent feedbacks act as a buffer against more frequent events.

Highlights

  • Extreme climate events often cause population crashes but are difficult to account for in population-dynamic studies

  • It has been suggested that high frequencies of bad years may lead to less variable population growth and, stabilized rather than destabilized population dynamics[11]

  • Because effects of environmental stochasticity are modified by internal density-dependent feedback, frequent extreme events dampen the population dynamics and even reduce the extinction risk

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Summary

Introduction

Extreme climate events often cause population crashes but are difficult to account for in population-dynamic studies. We show that the impact of an extreme ROS and icing event on reindeer survival, fecundity, and population growth rate is strongly ageand density-dependent.

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Conclusion
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