Articles | Volume 11, issue 2
Biogeosciences, 11, 381–407, 2014

Special issue: REgional Carbon Cycle Assessment and Processes (RECCAP)

Biogeosciences, 11, 381–407, 2014

Research article 28 Jan 2014

Research article | 28 Jan 2014

A full greenhouse gases budget of Africa: synthesis, uncertainties, and vulnerabilities

R. Valentini1,2, A. Arneth3, A. Bombelli2, S. Castaldi2,4, R. Cazzolla Gatti1, F. Chevallier5, P. Ciais5, E. Grieco2, J. Hartmann6, M. Henry7, R. A. Houghton8, M. Jung9, W. L. Kutsch10, Y. Malhi11, E. Mayorga12, L. Merbold13, G. Murray-Tortarolo15, D. Papale1, P. Peylin5, B. Poulter5, P. A. Raymond14, M. Santini2, S. Sitch15, G. Vaglio Laurin2,16, G. R. van der Werf17, C. A. Williams18, and R. J. Scholes19 R. Valentini et al.
  • 1Department for Innovation in Biological, Agro-food and Forest systems (DIBAF), University of Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy
  • 2Euro-Mediterranean Center on Climate Change (CMCC), Via Augusto Imperatore 16, 73100 Lecce, Italy
  • 3Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research, Kreuzeckbahn Str. 19, 82467 Garmisch-Partenkirchen, Germany
  • 4Dipartimento di Scienze Ambientali, Biologiche e Farmaceutiche (DISTABIF), Seconda Università di Napoli, via Vivaldi 43, 81100 Caserta, Italy
  • 5LSCE, CEA-CNRS-UVSQ, L'Orme des Merisiers, Bat 701, 91191 Gif-sur-Yvette, France
  • 6Institute for Biogeochemistry and Marine Chemistry, 20146, Hamburg, Germany
  • 7FAO, Forestry Department, UN-REDD Programme, Viale delle terme di Caracalla 1, 00153 Rome, Italy
  • 8Woods Hole Research Center, 149 Woods Hole Road, Falmouth, MA 02540, USA
  • 9Biogeochemical Model Data Integration Group, Max Planck Institute for Biogeochemistry, Hans-Knöll Str. 10, 07745 Jena, Germany
  • 10Thuenen Institute for Climate-smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany
  • 11Environmental Change Institute, School of Geography and the Environment, University of Oxford, South Parks Road, Oxford, OX1 3QY, UK
  • 12Applied Physics Laboratory, University of Washington, Seattle, WA 98105-6698, USA
  • 13Department of Environmental Systems Science, Institute of Agricultural Sciences IAS, ETH Zurich, 8092 Zurich, Switzerland
  • 14Yale School of Forestry and Environmental Studies, 195 Prospect St, New Haven, CT 06511, USA
  • 15University of Exeter, Rennes Drive, Exeter EX4 4RJ, UK
  • 16Department of Civil Engineering and Computer Science Engineering, University of Tor Vergata, Rome, Italy
  • 17Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
  • 18Graduate School of Geography, Clark University, Worcester, MA 01610, USA
  • 19Council for Scientific and Industrial Research, P.O.~Box 395, Pretoria 0001 South Africa

Abstract. This paper, developed under the framework of the RECCAP initiative, aims at providing improved estimates of the carbon and GHG (CO2, CH4 and N2O) balance of continental Africa. The various components and processes of the African carbon and GHG budget are considered, existing data reviewed, and new data from different methodologies (inventories, ecosystem flux measurements, models, and atmospheric inversions) presented. Uncertainties are quantified and current gaps and weaknesses in knowledge and monitoring systems described in order to guide future requirements. The majority of results agree that Africa is a small sink of carbon on an annual scale, with an average value of −0.61 ± 0.58 Pg C yr−1. Nevertheless, the emissions of CH4 and N2O may turn Africa into a net source of radiative forcing in CO2 equivalent terms. At sub-regional level, there is significant spatial variability in both sources and sinks, due to the diversity of biomes represented and differences in the degree of anthropic impacts. Southern Africa is the main source region; while central Africa, with its evergreen tropical forests, is the main sink. Emissions from land-use change in Africa are significant (around 0.32 ± 0.05 Pg C yr−1), even higher than the fossil fuel emissions: this is a unique feature among all the continents. There could be significant carbon losses from forest land even without deforestation, resulting from the impact of selective logging. Fires play a significant role in the African carbon cycle, with 1.03 ± 0.22 Pg C yr−1 of carbon emissions, and 90% originating in savannas and dry woodlands. A large portion of the wild fire emissions are compensated by CO2 uptake during the growing season, but an uncertain fraction of the emission from wood harvested for domestic use is not. Most of these fluxes have large interannual variability, on the order of ±0.5 Pg C yr−1 in standard deviation, accounting for around 25% of the year-to-year variation in the global carbon budget.

Despite the high uncertainty, the estimates provided in this paper show the important role that Africa plays in the global carbon cycle, both in terms of absolute contribution, and as a key source of interannual variability.

Final-revised paper