Salt of the earth: a critical impediment to herbivore range-shifts in response to climate change

Dr Kara Youngentob1, Dr Karen Marsh1, Professor  William Foley1

1Australian National University, Canberra, Australia

Sodium is essential to the survival of all mammals. It is the predominant cation circulating in the blood and it is necessary for many essential bodily functions, from osmotic homeostasis and nerve transmission, to reproduction and lactation. However, herbivores can struggle to obtain enough salt because it is typically less available in vegetation than other food resources. As a result, herbivores often go to great efforts to meet their sodium requirements and will consume dirt, bark, and other substances that are not typical of their foliage-based diet. The hunger for salt is even more pronounced in herbivore populations at higher elevations, since environmentally available sodium tends to decrease with increasing altitude. Sodium loss from upland areas is exacerbated by freeze-thaw cycles that break-up soil and combine with melting snow to leach-out soluble sodium. The transport and deposition of salt via aerosols also declines with distance from the ocean. Despite its importance to the survival of all animals, sodium and its availability can be overlooked in wildlife management and conservation, particularly in specialist folivores that are thought to meet the bulk of their nutritional requirements from leaves. This is particularly concerning given that many animals are predicted to move to higher elevations in response to climate change. A lack of environmentally available sodium could limit the upward range-shifts of many herbivorous animals unless alternative sources of this critical nutrient are available and can be exploited.


Dr Kara Youngentob is a Discovery Early Career Research Fellow at the Research School of Biology, Australian National University (ANU). She completed a PhD in Environment from  ANU in 2010 and a MSc in Wildlife Ecology and Conservation from the University of Florida in 2004. Her main interests are in applied ecological research to inform and improve wildlife management and conservation decisions.  She is also a big fan of science communication. Her current research looks at plant-animal interactions across landscapes to determine whether forage quality influences landscape use by herbivores. She also uses remote sensing methods to map the quality of forage for browsing herbivores with imaging spectroscopy and LiDAR.

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