title: The importance of considering animal body mass in IPCC greenhouse inventories and the underappreciated role of wild herbivores.
abstract: Methane is an important greenhouse gas, but characterizing production by source sector has proven difficult. Current estimates suggest herbivores produce ~20% (~76-189 Tg yr(-1) ) of methane globally, with wildlife contributions uncertain. We develop a simple and accurate method to estimate methane emissions and reevaluate production by wildlife. We find a strikingly robust relationship between body mass and methane output exceeding the scaling expected by differences in metabolic rate. Our allometric model gives a significantly better fit to empirical data than IPCC Tier 1 and 2 calculations. Our analysis suggests that (i) the allometric model provides an easier and more robust estimate of methane production than IPCC models currently in use; (ii) output from wildlife is much higher than previously considered; and (iii) because of the allometric scaling of methane output with body mass, national emissions could be reduced if countries favored more, smaller livestock, over fewer, larger ones.
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
authors.forename: Felisa A
authors.initials: FA
authors.lastname: Smith
authors.affiliation: Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20013, USA.
authors.forename: S Kathleen
authors.initials: SK
authors.lastname: Lyons
authors.affiliation: Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20013, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Wagner
authors.affiliation: Climate, Ocean, Sea Ice Modeling (COSIM), Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Elliott
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000818:Animals; D001835:Body Weight; D004784:Environmental Monitoring; D017752:Greenhouse Effect; D060434:Herbivory; D008322:Mammals / Q000502:physiology*; D008697:Methane / Q000032:analysis*; D008962:Models, Theoretical
chemical_list: D000393:Air Pollutants; D008697:Methane
keywords: IPCC Tier 1; IPCC Tier 2; allometry; enteric emissions; megaherbivores; methane; wild mammals