Grassland Carbon Management


Grasslands cover approximately 25% of the Earth’s land surface (approximately 3.4 billion ha) and contain roughly 12% of the terrestrial carbon stocks (1,2). Grasslands are dominated by herbaceous (nonwoody) vegetation and so—unlike forests—carbon within living aboveground vegetation is a small proportion of the total ecosystem carbon pool. Additionally, this aboveground biomass carbon is relatively short-lived due to harvest, grazing, fire, and senescence. In contrast, the perennial grasses that dominate grasslands are characterized by extensive fibrous root systems that often make up 60-80% of the biomass carbon in these ecosystems. 



Grasslands are used intensively for food and forage production globally because of their high natural soil fertility. Carbon stores within grasslands are sensitive to management and are thus vulnerable to losses in soil carbon. Land degradation—which is a long-term decline in plant productivity and the associated soil and water functions that support it—is widespread in grasslands in part due to soil carbon losses. More than 20% of the world’s croplands are degraded, as are 20-25% of the grasslands (4). These losses in soil carbon are attributed to several factors, particularly decreased carbon inputs to the soil. Activities such as harvesting plant biomass significantly decreases the amount of carbon contributing to soil organic matter from removal of aboveground biomass. Likewise, changes of plant species to favor species with greater aboveground production—such as the conversion from natural grassland to cropland or improved pasture—significantly reduces the belowground biomass in roots.

Text source: Ontl, T.; Janowiak, M. 2017. Grassland and Carbon Management. (June, 2017). U.S. Department of Agriculture, Forest Service, Climate Change Resource Center.