CES researchers discovered that this difference appears to be due to the use of veterinary antibiotics such as tetracycline on livestock in a study conducted in the Spiti region of the Himalayas and published in Global Change Biology.
According to the researchers, when antibiotics are released into the soil via dung and urine, they alter the microbial communities in the soil in ways that are detrimental to carbon sequestration.
"Livestock is now the most abundant large mammal on the planet. If the carbon stored in soil under livestock can be increased even slightly, it can have a significant impact on climate mitigation," as per Sumanta Bagchi, Associate Professor at CES and the study's corresponding author.
In a previous study, the researchers demonstrated how herbivore grazing plays an important role in stabilizing the pool of soil carbon in the same region. They set out to answer the question: Are livestock like sheep and cattle similar or different in how they affect soil carbon stocks than their wild relatives like yak and ibex?
To answer this, the researchers studied soils in areas grazed by wild herbivores and livestock for 16 years, analysing them for various parameters such as microbial composition, soil enzymes, carbon stocks, and the amount of veterinary antibiotics.
According to the study, while soils from the wild and livestock areas shared many similarities, they differed in one key parameter called carbon use efficiency (CUE), which determines microbes' ability to store carbon in the soil. The CUE of the soil in livestock areas was 19% lower.
Bagchi added that antibiotic use is relatively low in pastoral ecosystems such as Spiti and that the situation could be worse in areas where livestock are raised on large scales and are frequently given antibiotics even when they are not sick. Antibiotics, such as tetracycline, have a long half-life and can remain in the soil for decades, according to the study.
