Research has shown that grazing by musk oxen and other large herbivores could have a significant impact on Arctic greenhouse gas exchange
Arctic ecosystems, which contain huge amounts of carbon in their soils, are of great significance to global greenhouse gas exchange. While the Arctic region has generally acted as a carbon sink for the past 10,000 years, the impact of climate change has recently seen some areas transition towards carbon source status. Herbivores are an important part of many Arctic ecosystems and have been found to have an important impact on the carbon cycle in the region, mainly through their grazing. One of these herbivores is the musk ox, a large bovine noted for its thick coat, curved horns and the strong odour emitted by males during the seasonal rut (hence its name). Well-adapted to life in the frozen north, musk oxen roam the tundra in search of roots, mosses, and lichens. In winter, they use their hooves to dig through snow to graze, while in summer they supplement their diet with Arctic flowers and grasses, often feeding near water.
There are around 170,000 musk ox currently living across the circumpolar tundra, concentrated in Greenland and Canada. With the Earth’s climate rapidly warming, their future is uncertain.
In a study carried out by Swedish and Danish researchers in Greenland between 2011 and 2013, musk oxen were deliberately excluded from test areas by fencing. After several years the research team saw that a species of moss had grown strongly in these non-grazed test areas, which had hindered the growth of plants important for the absorption of CO2 and the production of CH4 (methane). This resulted in a 47 percent decrease in CO2 uptake and a 44 percent decrease in CH4 emissions.
The research team calculated that the net effect of excluding musk oxen from the test areas was to halve the positive impact of those areas on global warming. Despite the fact that the areas still grazed by musk oxen released more CH4 – a far more potent greenhouse gas than CO2 – this was compensated for by higher CO2 absorption. While both grazed and ungrazed areas acted as carbon sinks, the removal of the musk oxen meant plants only absorbed half as much carbon during the growing season.
Future research will help to improve our understanding of how herbivory and associated processes influence the carbon cycle within the Arctic. Nevertheless, it is already clear that the removal of grazing and trampling by musk ox and other large herbivores from Arctic ecosystems could rapidly alter the composition and structure of vegetation, with associated impacts on greenhouse gas exchange. It is important that herbivore populations, and their conservation, are taken into account in Arctic climate models.
The removal of the musk oxen meant plants only absorbed half as much carbon during the growing season
Muskox, Norway, Marc Eggert, Unsplash
Protecting muskox circumpolar in high Arctic mire ecosystems can sequester 30MtCO2 per year. That’s 75% of the fossil fuel emissions by Norway in 2022 (40.9 MtCO2/y) ¹
How do musk oxen help store carbon?
- Control Vegetation Growth: Musk oxen graze on Arctic plants like mosses, preventing their overgrowth, which allows more CO2-absorbing plants to flourish.
- Maintain Carbon Uptake: Grazing areas with musk oxen absorb more CO2 compared to areas where they are excluded. Musk oxen’s presence in an ecosystem increases plant productivity, boosting carbon capture.
- Modulate Methane and CO2 Exchange: Although musk oxen-grazed areas release more methane (CH4), the increase in CO2 absorption outweighs these emissions, making the net effect positive for reducing global heating.
- Prevent Carbon Sink Degradation: By maintaining vegetation balance, musk oxen help sustain the Arctic as a carbon sink, ensuring continued sequestration of carbon.
Current situation – what we need to do
Protecting musk ox populations is essential for maintaining carbon balance in Arctic ecosystems. Their grazing activity supports greater CO2 absorption, helping to mitigate climate change. Conservation efforts should prioritise the protection of musk ox habitats to sustain these critical carbon sinks.
(1) Note: These species data are from Table 1 and the Supplementary Appendix 1 of Schmitz, O.J., Sylvén, M., Atwood, T.B. et al. Trophic rewilding can expand natural climate solutions.
Nat. Clim. Chang. 13, 324–333 (2023). https://doi.org/10.1038/s41558-023-01631-6
Next steps
- Return to the main Climate Heroes page.
- Read all the original Climate Hero case studies in ‘Animating the Carbon Cycle: Supercharging Ecosystem Carbon Sinks to Meet the 1.5°C Climate Target’. Download the pdf here.
- Curious to learn more? Watch the video from the UN Climate Change Side Events at COP28: Bringing elephants into the room – why UNFCCC needs to put animals on the table.