Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 16
Biogeosciences, 13, 4789-4809, 2016
https://doi.org/10.5194/bg-13-4789-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 4789-4809, 2016
https://doi.org/10.5194/bg-13-4789-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Reviews and syntheses 29 Aug 2016

Reviews and syntheses | 29 Aug 2016

Greenhouse gas emissions from natural ecosystems and agricultural lands in sub-Saharan Africa: synthesis of available data and suggestions for further research

Dong-Gill Kim1, Andrew D. Thomas2, David Pelster3, Todd S. Rosenstock4, and Alberto Sanz-Cobena5 Dong-Gill Kim et al.
  • 1Wondo Genet College of Forestry and Natural Resources, Hawassa University, P.O. Box 128, Shashemene, Ethiopia
  • 2Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth SY23 3DB, UK
  • 3International Livestock Research Institute, P.O. Box 30709, Nairobi, Kenya
  • 4World Agroforestry Centre (ICRAF), P.O. Box 30677-00100, United Nations Avenue, Nairobi, Kenya
  • 5Technical University of Madrid, School of Agriculture, Avd. Complutense s/n, 28040 Madrid, Spain

Abstract. This paper summarizes currently available data on greenhouse gas (GHG) emissions from African natural ecosystems and agricultural lands. The available data are used to synthesize current understanding of the drivers of change in GHG emissions, outline the knowledge gaps, and suggest future directions and strategies for GHG emission research. GHG emission data were collected from 75 studies conducted in 22 countries (n = 244) in sub-Saharan Africa (SSA). Carbon dioxide (CO2) emissions were by far the largest contributor to GHG emissions and global warming potential (GWP) in SSA natural terrestrial systems. CO2 emissions ranged from 3.3 to 57.0MgCO2ha−1yr−1, methane (CH4) emissions ranged from −4.8 to 3.5kgha−1yr−1 (−0.16 to 0.12MgCO2 equivalent (eq.)ha−1yr−1), and nitrous oxide (N2O) emissions ranged from −0.1 to 13.7kgha−1yr−1 (−0.03 to 4.1MgCO2 eq.ha−1yr−1). Soil physical and chemical properties, rewetting, vegetation type, forest management, and land-use changes were all found to be important factors affecting soil GHG emissions from natural terrestrial systems. In aquatic systems, CO2 was the largest contributor to total GHG emissions, ranging from 5.7 to 232.0MgCO2ha−1yr−1, followed by −26.3 to 2741.9kgCH4ha−1yr−1 (−0.89 to 93.2MgCO2 eq.ha−1yr−1) and 0.2 to 3.5kgN2Oha−1yr−1 (0.06 to 1.0MgCO2 eq.ha−1yr−1). Rates of all GHG emissions from aquatic systems were affected by type, location, hydrological characteristics, and water quality. In croplands, soil GHG emissions were also dominated by CO2, ranging from 1.7 to 141.2MgCO2ha−1yr−1, with −1.3 to 66.7kgCH4ha−1yr−1 (−0.04 to 2.3MgCO2 eq.ha−1yr−1) and 0.05 to 112.0kgN2Oha−1yr−1 (0.015 to 33.4MgCO2 eq.ha−1yr−1). N2O emission factors (EFs) ranged from 0.01 to 4.1%. Incorporation of crop residues or manure with inorganic fertilizers invariably resulted in significant changes in GHG emissions, but results were inconsistent as the magnitude and direction of changes were differed by gas. Soil GHG emissions from vegetable gardens ranged from 73.3 to 132.0MgCO2ha−1yr−1 and 53.4 to 177.6kgN2Oha−1yr−1 (15.9 to 52.9MgCO2 eq.ha−1yr−1) and N2O EFs ranged from 3 to 4%. Soil CO2 and N2O emissions from agroforestry were 38.6MgCO2ha−1yr−1 and 0.2 to 26.7kgN2Oha−1yr−1 (0.06 to 8.0MgCO2 eq.ha−1yr−1), respectively. Improving fallow with nitrogen (N)-fixing trees led to increased CO2 and N2O emissions compared to conventional croplands. The type and quality of plant residue in the fallow is an important control on how CO2 and N2O emissions are affected. Throughout agricultural lands, N2O emissions slowly increased with N inputs below 150kgNha−1yr−1 and increased exponentially with N application rates up to 300kgNha−1yr−1. The lowest yield-scaled N2O emissions were reported with N application rates ranging between 100 and 150kgNha−1. Overall, total CO2 eq. emissions from SSA natural ecosystems and agricultural lands were 56.9±12.7 × 109MgCO2 eq.yr−1 with natural ecosystems and agricultural lands contributing 76.3 and 23.7%, respectively. Additional GHG emission measurements are urgently required to reduce uncertainty on annual GHG emissions from the different land uses and identify major control factors and mitigation options for low-emission development. A common strategy for addressing this data gap may include identifying priorities for data acquisition, utilizing appropriate technologies, and involving international networks and collaboration.

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African natural ecosystems and agricultural lands are a significant source of GHG. However, there are huge research gaps and understanding of Africa's contribution to global GHG emissions remains highly uncertain. The strategy for addressing this data gap involves identifying priorities for data acquisition, utilizing appropriate technologies, and establishing networks and collaboration.
African natural ecosystems and agricultural lands are a significant source of GHG. However,...
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