1Woods Hole Research Center, Falmouth, MA, USA
2Department of Geography, Cabot Institute, University of Bristol, Bristol, UK
3Department of Global Ecology, Carnegie Institution for Science, Stanford, USA
4Faculty of Earth and Life Sciences, VU University, Amsterdam, The Netherlands
5Ecology, Evolution, and Environmental Biology, Columbia University, New York, USA
6Department of Geographical Sciences, University of Maryland, College Park, USA
7Tyndall Centre for Climate Change Research, University of East Anglia, Norwich, UK
8Department of Geography, McGill University, Montreal, Canada
*now at: Max Planck Institute for Meteorology, Hamburg, Germany
Received: 12 Dec 2011 – Discussion started: 19 Jan 2012
Abstract. The net flux of carbon from land use and land-cover change (LULCC) accounted for 12.5% of anthropogenic carbon emissions from 1990 to 2010. This net flux is the most uncertain term in the global carbon budget, not only because of uncertainties in rates of deforestation and forestation, but also because of uncertainties in the carbon density of the lands actually undergoing change. Furthermore, there are differences in approaches used to determine the flux that introduce variability into estimates in ways that are difficult to evaluate, and not all analyses consider the same types of management activities. Thirteen recent estimates of net carbon emissions from LULCC are summarized here. In addition to deforestation, all analyses considered changes in the area of agricultural lands (croplands and pastures). Some considered, also, forest management (wood harvest, shifting cultivation). None included emissions from the degradation of tropical peatlands. Means and standard deviations across the thirteen model estimates of annual emissions for the 1980s and 1990s, respectively, are 1.14 ± 0.23 and 1.12 ± 0.25 Pg C yr−1 (1 Pg = 1015 g carbon). Four studies also considered the period 2000–2009, and the mean and standard deviations across these four for the three decades are 1.14 ± 0.39, 1.17 ± 0.32, and 1.10 ± 0.11 Pg C yr−1. For the period 1990–2009 the mean global emissions from LULCC are 1.14 ± 0.18 Pg C yr−1. The standard deviations across model means shown here are smaller than previous estimates of uncertainty as they do not account for the errors that result from data uncertainty and from an incomplete understanding of all the processes affecting the net flux of carbon from LULCC. Although these errors have not been systematically evaluated, based on partial analyses available in the literature and expert opinion, they are estimated to be on the order of ± 0.5 Pg C yr−1.
Revised: 10 May 2012 – Accepted: 18 Nov 2012 – Published: 13 Dec 2012
Houghton, R. A., House, J. I., Pongratz, J., van der Werf, G. R., DeFries, R. S., Hansen, M. C., Le Quéré, C., and Ramankutty, N.: Carbon emissions from land use and land-cover change, Biogeosciences, 9, 5125-5142, doi:10.5194/bg-9-5125-2012, 2012.