A Place for Animals in the Global Carbon Budget

Contributor(s): 
November 18, 2013

Understanding the global carbon budget is vital for managing climate change. Understanding the processes that regulate the carbon budget is critical to devising long-term conservation, mitigation, and restoration strategies. It is well known that through biogeochemical cycling processes, ecosystems around the globe remove and store vast quantities of carbon dioxide from the atmosphere, but typically only the contributions of plants and microbes are considered in these calculations because they make up most of the biomass of living organisms. However, a recent paper by Yale’s Oswald Schmitz (and others) suggests that we should also be studying the roles of animals in the carbon budget.

Animals obviously contribute greenhouse gases to the atmosphere through respiration and other metabolic pathways, but the authors argue that the larger contribution of animals to the carbon budget is through their indirect effects on the carbon storage and uptake activities of plants and microbes. For example, wildebeest herds in grassland/savanna ecosystems in East Africa dramatically decreased in size starting in the 1960s, leading to decreased grazing of grasslands and greater accumulation of plant material across the landscape. This plant material became fuel for large wildfires which led to increased release of carbon to the atmosphere. As the herds later became protected and increased in size, the amount of plant material decreased and fire sizes decreased, reducing the amount of carbon released.

Along with many other examples the paper makes it clear that through indirect mechanisms animals are capable of mediating the flux of carbon between ecosystems and the atmosphere. Therefore, ecosystem managers and policymakers that regularly grapple with local and regional carbon budgets may benefit by incorporating animal conservation into their management strategies.

Citations:

Schmitz O, PA Raymond, JA Estes, WA Kurz, GW Holtgrieve, ME Ritchie, DE Schindler, AC Spivak, RW Wilson, MA Bradford, V Christensen, L Deegan, V Smetacek, MJ Vanni, CC Wilmers (2013) Animating the carbon cycle. Ecosystems:DOI: 10.1007/s10021-10013-19715-10027