Wildlife and ecosystems with open canopies such as grasslands are rarely part of the discussions surrounding climate change mitigation. Now, a new review reports on the interactions between wild herbivores and vegetation to show how restoration efforts can be improved by aligning climate goals with biodiversity conservation.
Christensen, the paper’s lead author and a school colleague, said the idea that herbivores are necessarily harmful to carbon storage because they consume and disturb plants, “is too simple and risks poor land management decisions with bad consequences for biodiversity.” Geography and Environment, University of Oxford.
Describing grasslands as “neglected global repositories of carbon,” the research demonstrates how herbivores redistribute carbon from above-ground vegetation (where it is vulnerable to disturbances such as wildfire and disease) into more stable soil pools underground. Soil ponds consist primarily of undissolved plant and animal residues (particulate organic matter) and more resistant carbon stabilized by interaction with mineral soil particles (mineral-bound organic matter).
Christensen explained that by grazing, herbivores recycle plant matter back into the soil via dung and urine. The decomposers in the earth (mostly microbes, as well as large animals such as earthworms) feed on this nutrient-rich resource and bury parts of it in the soil. By increasing the amount of carbon circulated through the soil, Christensen and colleagues argue that ecosystems with larger herbivores may store a greater portion of total ecosystem carbon in ponds that are less susceptible to disturbance than the biomass of living plants.
The paper provides a comprehensive framework for the links between plants and large herbivores such as elephants and wild boars, and smaller organisms such as earthworms, dung beetles, and microbes. The research argues that the aboveground and underground carbon sequestration services provided by these living elements to the ecosystem should be viewed as a whole rather than as a series of individual foci.
Soil carbon is an important aspect, said Judith Setters, a researcher in forest and landscape ecology at Wageningen University and research that did not contribute to the new paper. Soil carbon is an important aspect, and the animals Herbivores improve soil carbon and nitrogen sequestration.Shepherds, though, was the lead author of a previous research paper that showed how megafauna (animals weighing more than 1,000 kilograms) increased both pools of carbon and nitrogen in the soil.Sitters added that the animals Huge ones like elephants and rhinos have a much greater impact on major ecosystem processes than smaller ones like zebras because of the amount of food they eat and the amount of dung they deposit.
A comprehensive view of the ecosystem
For millions of years, herbivores have been an integral part of how ecosystems function. The presence of herbivores alters “the quality and quantity of the food supply of soil microbes,” said Sumanta Bagshi, associate professor at the Center for Environmental Sciences and the Devicha Center for Climate Change at the Indian Institute of Science. In the absence of herbivores, Baggie said, “the time carbon remains in the soil less.”
Bagci was not involved in the new review, but he is one of the authors of a previous research paper that suggests why moderate levels of grazing can enhance net soil carbon storage in ecosystems. Maintaining the impact of large herbivores on grazing ecosystems through conservation and rebuilding efforts could be “of great importance” to soil carbon sequestration, Bagge said.
Christensen agreed, and suggested “a combination of climate-friendly forests, high-yield agriculture, more extensive semi-pastoral systems, and dedicated nature parks where biodiversity is prioritized” as the best way to improve multiple goals such as climate change mitigation and biodiversity conservation. .
Scientists like Bagchi, Sitters and Kristensen are not alone in highlighting the links between biodiversity and climate change. In 2020, two United Nations bodies (the Intergovernmental Panel on Climate Change and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) released a landmark report to highlight how the domains of climate change and biodiversity are “functionally separated”. Defining, understanding and dealing with the connections between the two is complete.”
—Rishika Bardekar (Tweet embed), a science writer