Antibiotics and livestock farming reduce carbon sequestration in grasslands

Livestock herbivores impact soil microbial fauna by reducing carbon uptake capacity, an Indian research says. Antibiotics’ effect on soil is crucial

by Matteo Cavallito

 

Not all herbivores are created equal, especially when it comes to their impact on soil and climate. That’s the message of a research conducted by the Indian Institute of Science (IISc) in Bangalore and published in the journal Global Change Biology. According to the survey, quoted by the U.S.-based NGO Mongabay, wild animals would have less noticeable effects on soil than livestock counterparts.

The finding takes on considerable importance, says Mongabay. Indeed, these animals “strongly influence the climate via their impacts on a large soil carbon stocks, with the world’s grasslands, steppes, and savannas storing an estimated 500 Petagrams (Pg) of carbon”.

The study

By comparing the effects of livestock and native herbivores, the authors found that the two groups differed in terms of their impact on vegetation composition. By analyzing soil carbon stocks from 2005-2016 and evaluating 17 different variables that influence the element’s presence in the soil, the researchers observed a different relationship with soil microbial processes. Which, in turn, have an effect on the amount of sequestered and retained carbon.

“Microbial carbon use efficiency (CUE) was 19% lower in soils under livestock. Compared to native herbivores, areas used by livestock contained 1.5 kg C m−2 less soil-C,” the research states.

In addition, “structural equation models showed that alongside the effects arising from plants, livestock alter soil microbial communities which is detrimental for CUE, and ultimately also for soil-C.” A species mix, according to the study, may reduce the impact. But livestock can never match wild herbivores in their ability to promote soil storage of the element.

Livestock farming antibiotics under fire

The research thus focuses on one of the main factors behind the different impact of animals: the use of antibiotics on livestock farms. Residues of these substances, which end up in the soil through animal manure, change the composition of the microbial community and reduce the ability of the microorganisms to process carbon by contributing to its storage.

“Supporting evidence pointed toward a link between veterinary antibiotics used on livestock, microbial communities, and soil-C,” the research further explains. “Overcoming the challenges of sequestering antibiotics to minimize their potential impacts on climate, alongside microbial rewilding under livestock, may reconcile the conflicting demands from food-security and ecosystem services.”

According to a research published in the Indian Journal of Medical Research in 2019, the livestock sector in the country is expected to grow 312 percent by the end of the decade. Currently, Mongabay notes, India is the world’s fourth largest consumer of antibiotics for animal use, after China, the United States and Brazil.

The role of grasslands

The study results consequently highlight the need to monitor and preserve the sequestration capacity of India’s huge grasslands and beyond. According to the FAO globally, the top 30 centimeters of grassland soils absorb 63.5 million tons of carbon annually. The highest stocks are found in temperate regions. The lowest in arid or semi-arid grasslands, which are characterized by low biomass production and decomposition of organic matter.

In East Asia, Central and South America, and southern Africa, however, researchers found a negative carbon balance. In those territories, in other words, current stocks of the organic element in soil are likely to decline due to anthropogenic stresses combined with climatic conditions. Adoption of best management practices, such as incorporation of animal manure, agroforestry and rotational grazing, the FAO still argues, would, by contrast, ensure excellent results in increasing soil-stored carbon.