Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 4 2 2007 10.5194/bg-4-215-2007 http://www.biogeosciences.net/4/215/2007/ http://www.biogeosciences.net/4/215/2007/bg-4-215-2007.html http://www.biogeosciences.net/4/215/2007/bg-4-215-2007.pdf 215 217 2007-04-10 Direct and indirect metabolic CO₂ release by humanity Y. T. Prairie C. M. Duarte carlosduarte@imedea.uib.es Département des sciences biologiques, Université du Québec à Montréal, Case postale 8888, succ. Centre-Ville, Montréal, H3C 3P8, Canada IMEDEA (CSIC-UiB), Instituto Mediterráneo de Estudios Avanzados, C/ Miquel Marqués 21, 07190 Esporles (Mallorca), Spain The direct CO₂ released by respiration of humans and domesticated animals, as well as CO₂ derived from the decomposition of their resulting wastes was calculated in order to ascertain the direct and indirect metabolic contribution of humanity to CO₂ release. Human respiration was estimated to release 0.6 Gt C year^−1 and that of their associated domestic animals was estimated to release 1.5 Gt C year^−1, to which an indirect release of 1.0 Gt C year^−1, derived from decomposition of the organic waste and garbage produced by humans and their domestic animals, must be added. These combined direct and indirect metabolic sources, estimated at 3.1 Gt C year^−1, have increased 7 fold since pre-industrial times and are predicted to continue to rise over the 21st century. Banegas, J. R., López-García, E., Gutiérrez-Fisac, J. L., Guallar-Castillón, P., and Rodríguez-Artalejo, F.: A simple estimate of mortality attributable to excess weight in the European Union, Eur. J. Clin. Nutr., 57, 201–208, 2003. Cohen, J. E.: How Many People Can the Earth Support?, New York, USA, W. W. Norton, 532, 1995. IPCC: Climate change 2001: The Scientific basis, New York, USA, Cambridge Univ. Press, 892, 2001. Marrieb, E. N.: Human Anatomy and Physiology, 5th edition, New York, USA, Benjamin/Cummings, 1237, 2000. OECD: Workshop on Waste Prevention: Toward Performance Indicators, Paris, France, OECD, 2002. FAO: World agriculture: towards 2015/2030, Summary report, Food and Agriculture Organization of the United Nations, Rome, Italy, 2002. Gitz, V. and Ciais, P.: Future expansion of agriculture and pasture acts to amplify atmospheric CO₂ levels in response to fossil-fuel and land-use change cmissions, Clim. Change, 67, 161–184, 2004. Pauly, D. and Christensen, V.: Primary production required to sustain global fisheries, Nature, $374$, 255–257, 1995. Peters, R. H.: The ecological implications of body size, New York, USA, Cambridge University Press, 1983. Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat: World Population Prospects: The 2002 Revision, http://esa.un.org/unpp, 2002. Robinson, W. R., Peters, R. H., and Zimmerman, J.: The effet of body size on the metabolic rates of organisms, Can. J. Zool., 61, 281–288, 1983. Tilman, D., Cassman, K. G., Matson, O. A., Naylor, R., and Polasky, S.: Agricultural sustainability and intensive production practices, Nature, 418, 671–673, 2002. Vitousek, P., Ehrlich, P. R., Ehrlich, A. H., and Matson, P.: Human appropriation of the products of photosynthesis, Bioscience, 36, 368–373, 1986.