title: Methane emission from global livestock sector during 1890-2014: Magnitude, trends and spatiotemporal patterns.
abstract: Human demand for livestock products has increased rapidly during the past few decades largely due to dietary transition and population growth, with significant impact on climate and the environment. The contribution of ruminant livestock to greenhouse gas (GHG) emissions has been investigated extensively at various scales from regional to global, but the long-term trend, regional variation and drivers of methane (CH4) emission remain unclear. In this study, we use Intergovernmental Panel on Climate Change (IPCC) Tier II guidelines to quantify the evolution of CH4emissions from ruminant livestock during 1890-2014. We estimate that total CH4emissions in 2014 was 97.1 million tonnes (MT) CH4or 2.72 Gigatonnes (Gt) CO2-eq (1 MT = 1012g, 1 Gt = 1015g) from ruminant livestock, which accounted for 47%-54% of all non-CO2GHG emissions from the agricultural sector. Our estimate shows that CH4emissions from the ruminant livestock had increased by 332% (73.6 MT CH4or 2.06 Gt CO2-eq) since the 1890s. Our results further indicate that livestock sector in drylands had 36% higher emission intensity (CH4emissions/km2) compared to that in nondrylands in 2014, due to the combined effect of higher rate of increase in livestock population and low feed quality. We also find that the contribution of developing regions (Africa, Asia and Latin America) to the total CH4emissions had increased from 51.7% in the 1890s to 72.5% in the 2010s. These changes were driven by increases in livestock numbers (LU units) by up to 121% in developing regions, but decreases in livestock numbers and emission intensity (emission/km2) by up to 47% and 32%, respectively, in developed regions. Our results indicate that future increases in livestock production would likely contribute to higher CH4emissions, unless effective strategies to mitigate GHG emissions in livestock system are implemented.
authors.affiliation: International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, USA.
authors.forename: Shree R S
authors.identifier: 0000-0001-9529-8206
authors.initials: SRS
authors.lastname: Dangal
authors.affiliation: International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, USA.|State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
authors.forename: Hanqin
authors.initials: H
authors.lastname: Tian
authors.affiliation: International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, USA.
authors.forename: Bowen
authors.initials: B
authors.lastname: Zhang
authors.affiliation: International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, USA.|State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
authors.forename: Shufen
authors.initials: S
authors.lastname: Pan
authors.affiliation: Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USA.
authors.forename: Chaoqun
authors.initials: C
authors.lastname: Lu
authors.affiliation: International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL, USA.
authors.forename: Jia
authors.initials: J
authors.lastname: Yang
mesh_terms: D000349:Africa; D000818:Animals; D001208:Asia; D057231:Climate Change; D058751:Livestock; D008697:Methane; D009609:Nitrous Oxide
chemical_list: D009609:Nitrous Oxide; D008697:Methane
keywords: IPCC Tier II; drylands; enteric fermentation; livestock; manure management; methane emission