Biogeosciences Discuss., 6, 2085-2123, 2009
© Author(s) 2009. This work is distributed
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
The Sub-Saharan Africa carbon balance, an overview
A. Bombelli1, M. Henry1,2,3, S. Castaldi4, S. Adu-Bredu5, A. Arneth6, A. de Grandcourt7,8, E. Grieco1, W. L. Kutsch9, V. Lehsten6, A. Rasile4, M. Reichstein9, K. Tansey10, U. Weber9, and R. Valentini1
1Department of Forest Environment and Resources (DISAFRI), University of Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy
2Institut de Recherche pour le Développement, IRD, UR SeqBio, SupAgro, Bat. 12, 2 place Viala, 34060 Montpellier Cedex 1, France
3AgroParisTech-ENGREF, GEEFT, 648 rue Jean-François Breton, BP 7355, 34086 Montpellier Cedex 4, France
4Dipartimento di Scienze Ambientali, Seconda Università di Napoli, via Vivaldi 43, 81100 Caserta, Italy
5Forestry Research Institute of Ghana (FORIG), P.O. Box 63 KNUST, Kumasi, Ghana
6Department of Physical Geography and Ecosystems Analysis (INES), Centre for GeoBiosphere Science, Lund University, Sölvegatan 12, 223 62, Lund, Sweden
7Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Persyst, UPR80, TA B-80/D, 34398 Montpellier Cedex 5, France
8Unité de recherche sur la productivité des plantations industrielles (UR2PI), BP 1291, Pointe Noire, République du Congo
9Max-Planck Institute for Biogeochemistry, Hans-Knöll Strasse 10, 07745 Jena, Germany
10Department of Geography, University of Leicester, Leicester, LE1 7RH, UK

Abstract. This study presents a summary overview of the carbon balance of Sub-Saharan Africa (SSA) by synthesizing the available data from national communications to UNFCCC and first results from the project CarboAfrica (net ecosystem productivity and emissions from fires, deforestation and forest degradation, by field and model estimates). According to these preliminary estimates the overall carbon balance of SSA varies from 0.43 Pg C y−1 (using in situ measurements for savanna NEP) to a much higher sink of 2.53 Pg C y−1 (using model estimates for savanna NEP). UNFCCC estimates lead to a moderate carbon sink of 0.58 Pg C y−1. Excluding anthropogenic disturbance and intrinsic episodic events, the carbon uptake by forests (0.98 Pg C y−1) and savannas (from 1.38 to 3.48 Pg C y−1, depending on the used methodology) are the main components of the SSA sink effect. Fires (0.72 Pg C y−1), deforestation (0.25 Pg C y−1) and forest degradation (0.77 Pg C y−1) are the main contributors to the SSA carbon emissions, while the agricultural sector contributes only with 0.12 Pg C y−1. Notably, the impact of forest degradation is higher than that caused by deforestation, and the SSA forest net carbon balance is close to equilibrium. Savannas play a major role in shaping the SSA carbon balance, due to their large areal extent, their fire regime, and their strong interannual NEP variability, but they are also a major uncertainty in the overall budget. This paper shows that Africa plays a key role in the global carbon cycle system and probably could have a potential for carbon sequestration higher than expected, even if still highly uncertain. Further investigations are needed, particularly to better address the role of savannas and tropical forests. The current CarboAfrica network of carbon measurements could provide future unique data sets for better estimating the African carbon balance.

Citation: Bombelli, A., Henry, M., Castaldi, S., Adu-Bredu, S., Arneth, A., de Grandcourt, A., Grieco, E., Kutsch, W. L., Lehsten, V., Rasile, A., Reichstein, M., Tansey, K., Weber, U., and Valentini, R.: The Sub-Saharan Africa carbon balance, an overview, Biogeosciences Discuss., 6, 2085-2123, doi:10.5194/bgd-6-2085-2009, 2009.
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