Arctic greening from warming promotes declines in caribou populations

• Published in: Science Advances
• Main Authors: Fauchald, Per, Park, Taejin, Tømmervik, Hans, Myneni, Ranga, Hausner, Vera Helene
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Science & technology; Multidisciplinary sciences; Tundra vegetation change; Sea-ice decline; Time series; Plant phenology; Herbivores; Climate; Arctic sea ice; Climate change; Normalized Difference Vegetation Index; Rangifer tarandus; Population dynamics; Caribou; Arctic; Arctic Ocean; Arctic Greening; Sea ice; Tundra
• Online Access: https://hdl.handle.net/2144/26696; https://www.ncbi.nlm.nih.gov/pubmed/28508037; https://doi.org/10.1126/sciadv.1601365

The migratory tundra caribou herds in North America follow decadal population cycles, and browsing from abundant caribou could be expected to counteract the current climate-driven expansion of shrubs in the circumpolar tundra biome. We demonstrate that the sea ice cover in the Arctic Ocean has provided a strong signal for climate-induced changes on the adjacent caribou summer ranges, outperforming other climate indices in explaining the caribou-plant dynamics. We found no evidence of a negative effect of caribou abundance on vegetation biomass. On the contrary, we found a strong bottom-up effect in which a warmer climate related to diminishing sea ice has increased the plant biomass on the summer pastures, along with a paradoxical decline in caribou populations. This result suggests that this climate-induced greening has been accompanied by a deterioration of pasture quality. The shrub expansion in Arctic North America involves plant species with strong antibrowsing defenses. Our results might therefore be an early signal of a climate-driven shift in the caribou-plant interaction from a system with low plant biomass modulated by cyclic caribou populations to a system dominated by nonedible shrubs and diminishing herds of migratory caribou.