Mismatch in reindeer resilience to past and future warming signals ongoing declines.

Abstract

<i>Rangifer tarandus</i> (caribou or reindeer) survived periods of abrupt climatic warming during the last deglaciation but are currently in global decline. Using process-explicit models of likely climate-human-<i>Rangifer</i> interactions and inferences of demographic change from radiocarbon-dated fossils and ancient DNA, we reconstruct and decipher 21,000 years of <i>Rangifer</i> population dynamics. These high-resolution population reconstructions pinpoint ecological characteristics and life-history traits that most likely enabled <i>Rangifer</i> to survive rapid warming events following the Last Glacial Maximum. Projecting these process-driven models into the future reveals that these attributes are unlikely to buffer <i>Rangifer</i> against wide-scale population declines from expected 21st Century climatic warming. Our findings highlight a need to boost investments in the management and conservation of <i>Rangifer</i>, particularly in North America, where projected losses are expected to exceed 80%. This will not only support the survival of the species and the vital services it renders in Arctic ecosystems, but also help sustain the socioeconomic, cultural, and emotional well-being of many <i>Rangifer</i>-dependent communities.