Large herbivores are highly dependent on their food sources such as mosses, lichens and grasses which are sensitive to climate change . Combined impacts of climate change and other inter-related factors suggest significant declines in caribou and reindeer populations, although to varying extents from one population to another . Warming has led to increased plant productivity and associated increases in body mass of some reindeer populations . Increasing primary production, warming will also change the plant composition, leading to increases in woody/shrubby vegetation which will have negative nutritional consequences for caribou and reindeer . The loss of lichens, a key winter food source, due to increased wildfire or replacement by grasses and herbs that die back in the winter, may also be detrimental to caribou and reindeer, although there is currently no consensus on this among experts . Rain on snow and icing events during winter, which are predicted to become more frequent, have been documented to lead to large increases in arctic herbivore mortality because they create an ice barrier making access to food more difficult . Rain-on-snow events may also impact reproductive success, although recent research suggests this relationship in not straightforward . Increased summer insect harassment is also predicted to increase and further stress large herbivores both by the additional parasitic load and by decreasing the amount of time spent grazing as animals seek to outrun pests . Finally, many caribou and reindeer populations rely on sea and freshwater ice to facilitate their movement and migration; loss of ice may make some populations no longer viable .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report