While shrubby species such as birch and willow are expected to proliferate in the Arctic under rising temperatures, grazing animals could restrain their growth, to the benefit of other species in the vegetative community. Greater diversity among plant species increases ecosystem stability.
In a study published in the journal Proceedings of the Royal Society of London (subscription required), Pennsylvania State University professor of biology Eric Post reported findings from a 10-year experiment conducted in Greenland that simulated global warming conditions in selected areas. Plant diversity was better maintained in those areas left open to caribou, musk ox and other herbivores than in those that excluded the animals. Post concludes that herbivorous grazing supports plant diversity by reducing the deleterious effects of shrubs’ shading and accumulation of leaf litter on competing species.
Earlier research has focused on the response of plant communties to changes in temperature, precipitation and nutrient availability. Post suggests that the interaction of species will influence the effects of a warming climate. He says, “Species interactions, such as exploitation, may thus buffer communities against destabilizing influences of climate change, and intact populations of large herbivores, in particular, may prove important in maintaining and promoting plant community diversity and stability in a changing climate.”
A similar study in Canada confirmed the importance of even small herds of caribou in controlling tundra plant growth. In a paper published in the Journal of Ecology (subscription required), the authors describe changes in shrub dominance resulting from caribou exclusion and call for consideration of browsing impacts in projecting changes in Arctic vegetation.