Abstract
Temperature is increasing in Arctic and sub-Arctic regions at a higher rate than anywhere else in the world. The frequency and nature of precipitation events are also predicted to change in the future. These changes in climate are expected, together with increasing human pressures, to have significant impacts on Arctic and sub-Arctic species and ecosystems. Due to the key role that reindeer play in those ecosystems, it is essential to understand how climate will affect the region’s most important species. Our study assesses the role of climate on the dynamics of fourteen Eurasian reindeer (Rangifer tarandus) populations, using for the first time data on reindeer abundance collected over a 70-year period, including both wild and semi-domesticated reindeer, and covering more than half of the species’ total range. We analyzed trends in population dynamics, investigated synchrony among population growth rates, and assessed the effects of climate on population growth rates. Trends in the population dynamics were remarkably heterogeneous. Synchrony was apparent only among some populations and was not correlated with distance among population ranges. Proxies of climate variability mostly failed to explain population growth rates and synchrony. For both wild and semi-domesticated populations, local weather, biotic pressures, loss of habitat and human disturbances appear to have been more important drivers of reindeer population dynamics than climate. In semi-domesticated populations, management strategies may have masked the effects of climate. Conservation efforts should aim to mitigate human disturbances, which could exacerbate the potentially negative effects of climate change on reindeer populations in the future. Special protection and support should be granted to those semi-domesticated populations that suffered the most because of the collapse of the Soviet Union, in order to protect the livelihood of indigenous peoples that depend on the species, and the multi-faceted role that reindeer exert in Arctic ecosystems.
Highlights
Terrestrial ecosystems in the Arctic and sub-Arctic are adapted to low-temperature regimes and considered to be extremely susceptible to rapid climate change, especially because temperature increase in these regions has been two to three times higher than in other parts of the world in recent decades [1]
The trends in the dynamics of the 19 reindeer populations we studied were very heterogeneous (Fig 1)
Trends in population dynamics were very variable across populations, as were the levels of synchrony among population growth rates, and the effects of climate
Summary
Terrestrial ecosystems in the Arctic and sub-Arctic are adapted to low-temperature regimes and considered to be extremely susceptible to rapid climate change, especially because temperature increase in these regions has been two to three times higher than in other parts of the world in recent decades [1]. Drivers of low Arctic tundra greening, where it is occurring, can be diverse even over distances of only a few dozen kilometers [3]. Herbivores are one such driver since they can counterbalance the effects of climate change on Arctic greening by limiting the growth of plants that would otherwise flourish at higher temperatures, such as shrubs and forbs [4,5]. Rangifer tarandus (including both reindeer and caribou, but hereafter referred to as reindeer) is the herbivore species with the highest potential to prevent greening in the Arctic. Most of the semi-domesticated reindeer populations feed on natural resources year-round and are integral to the functioning of Arctic social-ecological systems [6]
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