Grazing animals play a key role in stabilizing soil carbon

A new study led by the Indian Institute of Science (IISc) has revealed that large herbivores like yak play a very important role in the stability of soil carbon in grazing ecosystems. By studying soil composition in the Spiti region of the Himalayas, the researchers found that soil carbon levels are less stable in the absence of grazing animals. 

According to the experts, this phenomenon could have unintended negative consequences for the global carbon cycle, especially considering that soil contains more carbon than all plants and the atmosphere combined. Maintaining the stability of soil carbon is critical in helping to mitigate the negative effects of climate change, including global warming. 

Study senior author Sumanta Bagchi is a professor at the Centre for Ecological Sciences (CES) who began studying the impact of grazing animals on Himalayan ecosystems back in 2005. Bagchi led a long-term research project that was made possible with support from the Himachal Pradesh state government, local authorities, and the people of the Kibber village in Spiti.

The researchers created fenced plots without animals, as well as plots with grazing animals like yak and ibex. Over the following decade, Bagchi and his students collected soil samples from the plots. Each year, the team analyzed the chemical composition of the soil, tracking and comparing the levels of carbon and nitrogen in each plot.

The study revealed that soil carbon fluctuated 30 to 40 percent more in the fenced plots without grazing animals. In the grazed plots, soil carbon remained more stable. 

Study first author Dilip GT Naidu explained that many previous studies have focused on measuring carbon and nitrogen levels at long time intervals, assuming that the accumulation or loss of carbon is a slow process. However, he said the interannual fluctuations the team noticed in their data paint a very different picture.

According to the researchers, since grazing ecosystems make up about 40 percent of Earth’s land surface, protecting the herbivores that keep the soil carbon stable should remain a key priority for mitigating climate change.

“Both domestic and wild herbivores influence climate via their effects on soil carbon,” explained study co-author Shamik Roy. The CES team is also investigating how the ecosystem impacts of domestic herbivores, such as goats and sheep, differ from the effects of wild grazing animals. 

“Domestic and wild herbivores are very similar in many respects, but they differ in how they influence plants and soil,” said Roy. “Understanding why they are not alike can lead us toward more effective stewardship of soil carbon.”

The study is published in the journal Proceedings of the National Academy of Sciences.

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By Chrissy Sexton, Earth.com Editor

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