Wild animals play a critical role in shaping ecosystems, with apex predators often having the greatest impact, despite their relatively modest population size. This happens because predators, herbivores, plants, and decomposers interact in complex food webs. While it has long been known that such webs support ecosystem resilience, it is now becoming clear that some trophic cascades could also have a significant impact on the carbon cycle and climate emergency.
As apex predators with an extensive geographical range, wolves could have a major influence on carbon sequestration. The carbon footprint of wolves depends on what they kill. This, in turn, depends on where they are living. A study carried out in 2016 examined the potential for wolves to have cascading effects on carbon cycling within two very different North American ecosystems: boreal forest inhabited by moose, and grassland inhabited by elk (wapiti).
The boreal forest of North America – a vast expanse of spruce, hemlock, pine and fir – is one of the most significant carbon-storing landscapes on the planet. Wolves have an outsized influence on the boreal ecosystem through their predation. Moose – as the dominant herbivore – also shape the composition of the forest, and microbes in the soil, because they feed heavily on shoots and leaves.
The 2016 study found that when healthy wolf populations are present in the boreal forest, they directly influence both the foraging behaviour and abundance of moose. This changes the way moose interact with boreal plant communities, which alters the forest composition and increases tree biomass. The end result is that wolves enhance carbon storage in both plants and soils.
By extrapolating their results, the study team estimated that wolves could (with a number of caveats) increase carbon storage in North American boreal forest by up to 99 million tonnes a year, compared to an ecosystem without wolves. The protection of wolf populations across the entire North American boreal region could therefore safeguard the sequestration of carbon equivalent to 10 percent of CO2 emissions in the US.
Wolves could increase carbon storage in North American boreal forest by up to 99 million tonnes a year, compared to an ecosystem without wolves
Protecting grey wolf in Boreal Canada can sequester 260 MtCO2 per year. That’s 47% of the total fossil fuel emissions by Canada in 2022 (548 MtCO2/y) ¹
The situation in North American grasslands is very different, where the presence of wolves may actually decrease the amount of carbon stored in the landscape. Here, elk stimulate the growth of grass by excreting what they eat and fertilising the soil. In this scenario, an increase in the number of wolves may decrease the abundance of elk and thereby significantly suppress carbon storage. If wolves and elk co-existed across the entire expanse of North American high-altitude grassland, the 2016 study team estimated a loss of carbon storage of up to 30 million tonnes a year.
The study team subtracted the loss of carbon storage attributable to wolves throughout North American grasslands from the increase in carbon storage attributable to wolves in North American boreal forest. They found the potential net effect was of the same order of magnitude as the removal of between 6 and 20 million passenger vehicles per year. These figures are only estimates and far more research is required, but they indicate the scale of the potential impact of top predators on terrestrial ecosystem carbon cycling.
Wolves infographic based on oroginal design by GRID-Arendal
How do wolves help store carbon?
- Control Herbivore Populations: Wolves regulate herbivore species like moose, whose unchecked feeding on plants can suppress tree growth and reduce carbon storage.
- Alter Herbivore Behavior: The presence of wolves causes moose to change their foraging habits, which allows plant communities to regenerate and thrive, increasing tree biomass.
- Enhance Carbon Sequestration: By reducing moose over-browsing, wolves promote healthier forests, which store more carbon in both plant biomass and soils.
- Impact on Boreal Forests: In North American boreal forests, wolves could increase carbon storage by up to 99 million tonnes annually, by maintaining balanced ecosystems that support tree growth and soil health.
Current situation – what we need to do
The recovery and protection of grey wolf populations in North America’s boreal forests are vital to improving carbon sequestration. Wolves help regulate moose populations, which in turn supports healthier, carbon-rich forests. Conservation efforts should focus on ensuring the survival of wolf populations, especially in boreal regions where their presence has the most significant positive impact on carbon storage. Further research is needed to understand the full scope of their influence on different ecosystems, but restoring wolves in key areas is a promising strategy for natural climate solutions.
(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.