24 January 2023

Herbivores are a surprising ally of climate and soil

Far from being destructive, herbivores contribute to climate change mitigation, according to a new research. Their ability to prevent wildfires and return carbon and seeds to the soil is crucial

by Matteo Cavallito

 

Contrary to what you might think, the Earth’s large herbivores can play an important role in countering climate change. This is suggested by a research published in the journal Current Biology. Indeed, the study, taken up by the U.S.-based NGO Mongabay, highlights how these animals end up implementing a number of mechanisms that prove, in their own way, to be effective mitigation strategies.

Animals, in particular, “help prevent fires, decrease the amount of solar heat absorbed by the Earth’s surface, and contribute a lot to the long-term storage of carbon in soil,” said Yadvinder Malhi, an ecosystem expert at the University of Oxford and lead author of the research. Mammals such as elephants, wildebeests and the like, the organization then notes, “may be helping, not hindering, our carbon storage efforts.”

A successful firefighting effort

Interactions between large animals and climate, the researchers remind, can sometimes be problematic, just like the complex relationship between fauna and soil, we may say. Emblematic in this regard is the case of the surprising balance established millions of years ago between the soil and colossal herbivores of the time, the dinosaurs. A mysterious ecosystem mechanism that continues to challenge scientists’ understanding. Returning to the present day, the research photographs a situation that is surprising in some ways.

While seemingly destructive to vegetation, in fact, large herbivores appear to have “the greatest potential to facilitate climate change mitigation at a global scale via three mechanisms.”

Namely, the scientists explain, “changes in the fire regime, expecially in mesic grasslands or warm temperate woodlands.” But also “changes in terrestrial albedo and increases in soil carbon stocks,” particularly in temperate, tropical and subtropical lowland ecosystems.

The virtuous carbon circle

According to the study authors, by eating plant material, herbivores remove potential fuel from fires. At the same time, much of the carbon stored in consumed vegetation is quickly returned to the soil in the form of manure. The decomposition of dung allows the carbon to remain unaltered in the soil even if the flames spread.

In addition, explains Jens-Christian Svenning, a professor at Aarhus University in Denmark, “this carbon may increase the productivity of the soil, allowing many new plants to grow and absorb more CO2.”

Recent research, he says, “also suggests that grazing by wild herbivores may stimulate the release of substances from roots that stabilize soil carbon.” Finally, the same food cycle allows animals that consume plant fruits to return the seeds contained in them to the soil.

Animals are crucial not just in the tropics

The positive effect of the action of herbivores is not only found in areas characterized by a warm climate. In the Arctic, for example, these specimens help control the growth of woody plants, preventing them from spreading northward as temperatures rise.

In their territories, large native or reintroduced grazing animals, such as musk oxen, keep shrubs low, reducing solar energy absorption.

Herbivores, in particular, protect permafrost by compacting snow with their hooves, reducing its insulating effect and increasing the likelihood that soil temperatures will remain below freezing. In this way, the carbon-rich soil material does not decompose releasing the element into the atmosphere.

Conservation of herbivores is the key

In this scenario, conservation plays a crucial role. In the past, scientists note, for example, it is estimated that the extinction of large plant-eating mammals, such as mammoths for example, may have increased the average temperatures recorded in Siberia by 1°C. More recently, Africa has experienced a sharp decline in the presence of large wild animals, whose numbers were reportedly reduced by 59 percent in protected areas between 1970 and 2005.

Malhi and Svenning, Mongabay reminds us, argue that protecting herbivores and other wildlife will be critical to keeping ecosystems healthy. Doing so will simultaneously counter the twin crises of biodiversity and climate. “With just a few percent of the budget currently available for climate mitigation and adaptation, we could expand existing conservation efforts,” Malhi explains. “And also restore large animals where they have disappeared.”