Climate impact of livestock and wild herbivores

An Indian Institute of Science (IISc) study finds that livestock and wild herbivores differ in impacts on soil carbon and ultimately the climate, as reported by Mongabay-India.

As the Mongabay-India report states, the findings from the IISc Bengaluru study, published in Global Change Biology, build on previous research from the IISc in Spiti in the Indian state of Himachal Pradesh, which highlighted the role of ‘herbivores’ or grass-eating mammals in stabilising soil carbon. How herbivores impact soil carbon is of interest to scientists as these animals strongly influence the climate via their impacts on large soil carbon stocks, with the world’s grasslands, steppes, and savannas storing an estimated 500 Petagrams (Pg) of carbon. A Petagram is equal to 1015 grams. Large herbivores such as yak and ibex play a crucial role in this process.

The study highlights that given the increasing use of veterinary antibiotics on domestic animals, which eventually enter soil and affect the soil microbes, antibiotics pollution in soil also could have a very large impact on climate.

The abstract of the study says that grazing by large mammalian herbivores impacts climate as it can favour the size and stability of a large carbon pool in the soils of grazing ecosystems. As native herbivores in the world’s grasslands, steppes, and savannas are progressively being displaced by livestock, it is important to ask whether livestock can emulate the functional roles of their native counterparts. While livestock and native herbivores can have remarkable similarity in their traits, they can differ greatly in their impacts on vegetation composition which can affect soil-C. It is uncertain how these similarities and differences impact soil carbon via their influence on microbial decomposers.

In the study, the IISc scientists went on to examine whether livestock and native herbivores impact vegetation and soil carbon pools similarly. They found that the two groups differ in their impacts on vegetation composition, with herb-and-grass vegetation dominating in areas with native herbivores, and sedges in areas under livestock. Scientists attribute the differences to their diet selectivity. On the whole, a mix of diverse livestock comprising many different species can be somewhat similar in their impact on soil carbon as native herbivores, “but livestock do not emerge as perfect substitutes since they store less soil carbon.” In effect, the study points out that livestock cannot entirely replace native grass-munching herbivores in their ability to store soil carbon.

An added dimension to the native herbivores versus domesticated livestock issue that the Mongabay-India report finds in the study is the increasing use of antibiotics on livestock, which has been found to affect soil microbes and ultimately soil carbon storage. Extensive use of antibiotics on livestock may restrict soil carbon by altering soil microbial ‘carbon use efficiency’ or the efficiency with which microorganisms convert absorbed carbon into their own biomass. The findings highlight the importance of continued conservation of native herbivores and new ideas to improve livestock management. They suggest that sequestering antibiotics, along with the restoration and rewilding of soil microbial communities may offer nature-based climate solutions by improving soil carbon storage in areas under livestock. The study’s abstract also adds that overcoming the challenges of sequestering antibiotics to minimize potential impacts on climate, alongside microbial rewilding under livestock, may reconcile the conflicting demands from food-security and ecosystem services. Conservation of native herbivores and alternative management of livestock is crucial for soil carbon stewardship to envision and achieve natural climate solutions.

The Mongabay-India report also draws attention to a 2019 analysis in the Indian Journal of Medical Research. This analysis states that India is an important producer of food animals for the global market in the form of meat, meat products and farmed seafood and a rise by 312% is expected by 2030. Antimicrobial agents are widely used to prevent diseases in these farmed animals and to increase productivity. India is the world’s fourth largest consumer of antimicrobials for animal use, after China, USA and Brazil. Projections show that at this pace, India will contribute to the largest relative increase in antimicrobial consumption for use in livestock between 2010 and 2030.

The Mongabay-India report also highlights another August 2022 report of Future Markets Insights that says the global veterinary antibiotics market was worth $10904.3 million in 2022 and is projected to rise to $20,277 million in 2032 at a compound annual growth rate of 5.8%. The expanding animal healthcare industry, combined with the industry’s ongoing innovation, is driving the veterinary antibiotics market.