The role of South American grazing lands in mitigating greenhouse gas emissions. A reply to: “Reassessing the role of grazing lands in carbon-balance estimations: Meta-analysis and review”, by Viglizzo et al., (2019)

DELLA CHIESA, T.; BAZZONI, B.; ALVAREZ, R.; CARVALHO, P; OESTERHELD, M.; PRAVIA, V; VILLARINO, S.H.; JOBBÁGY, E.G; CONTI, G; BODDEY, R.; FERNANDEZ, R; OYHANTCABAL, W.; PIÑEIRO, G.; PINTO P.; STUDDERT, G.A.; RUFINO, M.; BAYER, C; LATTANZI, F; PARUELO J.M

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020 vol. 740 p. 108 - 140

0048-9697

The paper by Viglizzo et al. (2019) ?Reassessing the role of grazinglands in carbon-balance estimations: Meta-analysis and review? proposeda new methodology to assess changes in soil organic carbon (SOC) stockassociated with land use, and applied it to four countries of SouthAmerica: Argentina, Brazil, Paraguay, and Uruguay, all members of theMERCOSUR trade bloc. One finding of their assessment was that grazinglands are currently accumulating SOC at rates high enough to?... generateC surpluses that could not only offset rural emissions, but could also partiallyor totally offset the emissions of non-rural sectors?. Understandably, theseresults raised interest among local farmers and stakeholders, becausethey could have enormous implications for the design and implementation of national policies, in particular the Nationally Determined Contributions (NDCs) to the Paris Agreement of the United Nations FrameworkConvention on Climate Change (UNFCCC), as well as actions related tobuilding competitive advantages in international markets.Viglizzo et al. (2019) builds on the premise that the grazing lands ofthe MERCOSUR region are not in a steady state, and therefore their SOCstocks are not in equilibrium. Without further testing this hypothesis,they propose a new method to estimate changes in SOC stocks (?revisedmethod?), as an alternative to the simplified, but widely accepted IPCCTier 1 method (IPCC, 2006, 2019). This new ?revised method?, presentedagain in Ricard and Viglizzo (2020), is based on two complementary approaches: (i) a new equation that estimates SOC formation from belowground carbon inputs (named the ?Theoretical assessment?), and (ii) aworldwide literature review of SOC shifts following different land usechanges (named the ?Empirical assessment?). Although we agree thatgrazing lands may not be at equilibrium, we found two major flaws intheir manuscript that overestimate the potential SOC sequestration ingrazing lands and, thus, in our view invalidate their main conclusions.