In greening Arctic, caribou and muskoxen play key role: Study links grazing with plant phenology and abundance
The story of Arctic greening has overlooked some main characters. At center stage are climate change and warming temperatures. Meanwhile, large grazing wildlife, such as caribou and muskoxen, also play a key role in the timing ...
The study, published today in the journal PNAS Nexus, highlights the importance of large herbivores to the Arctic ecosystem, linking grazing with plant phenology and abundance in the Arctic tundra.
Phenology is the study of the timing and cyclical patterns in nature, such as when birds migrate, or when a plant first sprouts or blooms. Understanding such patterns is critically important in the Arctic, which is warming faster than anywhere on Earth.
"Caribou and muskoxen play a key role in how soon plants emerge and this translates to how abundant they become," said lead author Eric Post, a professor and arctic ecologist in the UC Davis Department of Wildlife, Fish and Conservation Biology. "This is an important, and overlooked, factor we need to consider as we seek to more fully understand climate change impacts on tundra vegetation in the Arctic."
Exclusion experiment
The research was conducted at a long-term study site near Kangerlussuaq, Greenland, where Post has been studying plant and animal interactions for 22 years. To understand how herbivores affect the timing of plant growth and abundance, the scientists excluded caribou and muskoxen from some study areas. From 2009 to 2017, they compared the timing of spring green-up of nine plant species with and without the grazing animals.
In general, plants where caribou or muskoxen were present experienced earlier green-up and greater abundance later in the growing season. About two-thirds of plants greened up earlier, and three-quarters were more abundant later in the season compared to plots without grazing. These include arctic draba and gray willow.
A group of muskoxen gather on the Arctic tundra near Kangerlussuaq, Greenland. Credit: Jeff Kerby
A field blooms with Arctic harebell near Kangerlussuaq, Greenland. In general, plants here greened up earlier and more abundantly in places where caribou or muskoxen graze. Harebell was one of the few species that emerged later when grazers were present. Credit: Eric Post, UC Davis
Many caribou populations in the Arctic are in decline, including migratory tundra caribou like this one. Meanwhile, new studies show that large herbivores in the Arctic are important for climate resilience. Credit: Eric Post, UC Davis