Aim: The accurate mapping of forest carbon stocks is essential for understanding the global carbon cycle, for assessing emissions from deforestation, and for rational land-use planning. Remote sensing (RS) is currently the key tool for this purpose, but RS does not estimate vegetation biomass directly, and thus may miss significant spatial variations in forest structure. We test the stated accuracy of pantropical carbon maps using a large independent field dataset. Location: Tropical forests of the Amazon basin. The permanent archive of the field plot data can be accessed at: http://dx.doi.org/10.5521/FORESTPLOTS.NET/2014_1 Methods: Two recent pantropical RS maps of vegetation carbon are compared to a unique ground-plot dataset, involving tree measurements in 413 large inventory plots located in nine countries. The RS maps were compared directly to field plots, and kriging of the field data was used to allow area-based comparisons. Results: The two RS carbon maps fail to capture the main gradient in Amazon forest carbon detected using 413 ground plots, from the densely wooded tall forests of the north-east, to the light-wooded, shorter forests of the south-west. The differences between plots and RS maps far exceed the uncertainties given in these studies, with whole regions over- or under-estimated by >25%, whereas regional uncertainties for the maps were reported to be <5%. Main conclusions: Pantropical biomass maps are widely used by governments and by projects aiming to reduce deforestation using carbon offsets, but may have significant regional biases. Carbon-mapping techniques must be revised to account for the known ecological variation in tree wood density and allometry to create maps suitable for carbon accounting. The use of single relationships between tree canopy height and above-ground biomass inevitably yields large, spatially correlated errors. This presents a significant challenge to both the forest conservation and remote sensing communities, because neither wood density nor species assemblages can be reliably mapped from space. © 2014 The Authors. Global Ecology and Biogeography published by John Wiley & Sons Ltd..238935946Aragão, L.E.O., Malhi, Y., Metcalfe, D.B., Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils (2009) Biogeosciences, 6, pp. 2759-2778Asner, G.P., Clark, J.K., Mascaro, J., Galindo García, G.A., Chadwick, K.D., Navarrete Encinales, D.A., Paez-Acosta, G., Ordóñez, M.F., High-resolution mapping of forest carbon stocks in the Colombian Amazon (2012) Biogeosciences, 9, pp. 2683-2696Baccini, A., Goetz, S.J., Walker, W.S., Laporte, N.T., Sun, M., Sulla-Menashe, D., Hackler, J., Houghton, R., Estimated carbon dioxide emissions from tropical deforestation improved by carbon-density maps (2012) Nature Climate Change, 2, pp. 182-185Baker, T.R., Phillips, O.L., Malhi, Y., Almeida, S., Arroyo, L., Di Fiore, A., Erwin, T., Vásquez Martínez, R., Variation in wood density determines spatial patterns in Amazonian forest biomass (2004) Global Change Biology, 10, pp. 545-562Banin, L., Feldpausch, T.R., Phillips, O.L., What controls tropical forest architecture? Testing environmental, structural and floristic drivers (2012) Global Ecology and Biogeography, 21, pp. 1179-1190Caravani, A., Nakhooda, S., Watson, C., (2012) The evolving global climate finance architecture, , Overseas Development Institute, Heinrich Böll Stiftung, Washington, DCChave, J., Andalo, C., Brown, S., Cairns, M.A., Chambers, J.Q., Eamus, D., Fölster, H., Yamakura, T., Tree allometry and improved estimation of carbon stocks and balance in tropical forests (2005) Oecologia, 145, pp. 87-99Chave, J., Coomes, D., Jansen, S., Lewis, S.L., Swenson, N.G., Zanne, A.E., Towards a worldwide wood economics spectrum (2009) Ecology Letters, 12, pp. 351-366Diaz, D., Hamilton, K., Johnson, E., (2011) State of the forest carbon markets 2011, , Forest Trends Association, Washington, DC(2010) Global forests resources assessment 2010, , FAO Forestry Paper 163. Food and Agriculture Organization, Rome, ItalyFearnside, P.M., Greenhouse gases from deforestation in Brazilian Amazonia: net committed emissions (1997) Climatic Change, 35, pp. 321-360Feldpausch, T.R., Banin, L., Phillips, O.L., Height-diameter allometry of tropical forest trees (2011) Biogeosciences, 8, pp. 1081-1106Feldpausch, T.R., Lloyd, J., Lewis, S.L., Tree height integrated into pantropical forest biomass estimates (2012) Biogeosciences, 9, pp. 3381-3403Fritz, S., Bartholomé, E., Belward, A., (2003) Harmonisation, mosaicing and production of the Global Land Cover 2000 database, , European Commission Joint Research Centre, Brussels(2009) A sourcebook of methods and procedures for monitoring and reporting anthropogenic greenhouse gas emissions and removals caused by deforestation, gains and losses of carbon stocks in forests, remaining forests, and forestation, , GOFC-GOLD GOFC-GOLD Land Cover Project Office, Wageningen University, Wageningen, The NetherlandsGutierrez-Velez, V.H., Pontius Jr, R.G., Influence of carbon mapping and land change modelling on the prediction of carbon emissions from deforestation (2012) Environmental Conservation, 39, pp. 325-336Houghton, R.A., Lawrence, K.T., Hackler, J.L., Brown, S., The spatial distribution of forest biomass in the Brazilian Amazon: a comparison of estimates (2001) Global Change Biology, 7, pp. 731-746(2012) Projecto PRODES: monitoramento da floresta amazônica Brasileira por satélite, , http://www.obt.inpe.br/prodes/index.php, INPE Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil. Available at: (accessed 2 November 2012)Lefsky, M.A., Harding, D.J., Keller, M., Cohen, W.B., Carabajal, C.C., Del Bom Espirito-Santo, F., Hunter, M.O., de Oliveira, R., Estimates of forest canopy height and aboveground biomass using ICESat (2005) Geophysical Research Letters, 32. , L22S02Lopez-Gonzalez, G., Lewis, S.L., Burkitt, M., Baker, T.R., Phillips, O.L., (2009) Forestplots.net database, , http://www.forestplots.net/, University of Leeds, Leeds, UK. Available at: (accessed 13 June 2013)Lopez-Gonzalez, G., Lewis, S.L., Burkitt, M., Phillips, O.L., ForestPlots.net: a web application and research tool to manage and analyse tropical forest plot data (2011) Journal of Vegetation Science, 22, pp. 610-613Lopez-Gonzalez, G., Mitchard, E.T.A., Feldpausch, T.R., (2014), http://dx.doi.org/10.5521/FORESTPLOTS.NET/2014_1, Amazon forest biomass measured in inventory plots. Plot Data from 'Markedly divergent estimates of Amazon forest carbon density from ground plots and satellites'Malhi, Y., Phillips, O.L., Lloyd, J., Baker, T., Wright, J., An international network to monitor the structure, composition and dynamics of Amazonian forests (RAINFOR) (2002) Journal of Vegetation Science, 13, pp. 439-450Malhi, Y., Wood, D., Baker, T.R., The regional variation of aboveground live biomass in old-growth Amazonian forests (2006) Global Change Biology, 12, pp. 1107-1138Olson, J.S., Watts, J.A., Allison, L.J., (1983) Carbon in live vegetation of major world ecosystems. TR004, , Oak Ridge National Laboratory, Oak Ridge, TNPenman, J., Gytarsky, M., Hiraishi, T., Krug, T., Kruge, D., Pipatti, R., Buendia, L., Wagner, F., (2003) Good practice guidance for land use, land-use change and forestry, , Intergovernmental Panel on Climate Change, GenevaPhillips, O.L., Lewis, S.L., Baker, T.R., Chao, K.-J., Higuchi, N., The changing Amazon forest (2008) Philosophical Transactions of the Royal Society B: Biological Sciences, 363, pp. 1819-1827Phillips, O.L., Baker, T.R., Feldpausch, T.R., Brienen, R., (2009), http://www.geog.leeds.ac.uk/projects/rainfor/, Field manual for plot establishment and remeasurement. Available at: (accessed 2 January 2013)Phillips, O.L., Aragão, L.E.O.C., Lewis, S.L., Drought sensitivity of the Amazon Rainforest (2009) Science, 323, pp. 1344-1347Potapov, P., Yaroshenko, A., Turubanova, S., Dubinin, M., Laestadius, L., Thies, C., Aksenov, D., Zhuravleva, I., Mapping the world's intact forest landscapes by remote sensing (2008) Ecology and Society, 13, p. 51Quesada, C.A., Phillips, O.L., Schwarz, M., Basin-wide variations in Amazon forest structure and function are mediated by both soils and climate (2012) Biogeosciences, 9, pp. 2203-2246Saatchi, S.S., Houghton, R.A., Alvalá, R., Soares, J.V., Yu, Y., Distribution of aboveground live biomass in the Amazon basin (2007) Global Change Biology, 13, pp. 816-837Saatchi, S.S., Harris, N.L., Brown, S., Lefsky, M., Mitchard, E.T.A., Salas, W., Zutta, B.R., Morel, A., Benchmark map of forest carbon stocks in tropical regions across three continents (2011) Proceedings of the National Academy of Sciences USA, 108, pp. 9899-9904Ter Steege, H., Pitman, N., Sabatier, D., A spatial model of tree α-diversity and tree density for the Amazon (2003) Biodiversity and Conservation, 12, pp. 2255-2277Ter Steege, H., Pitman, N.C.A., Phillips, O.L., Chave, J., Sabatier, D., Duque, A., Molino, J.-F., Vásquez, R., Continental-scale patterns of canopy tree composition and function across Amazonia (2006) Nature, 443, pp. 444-447(2012), http://www.state.gov/documents/organization/156214.pdf, U.S. Agency for International Development () Executive budget summary: function 150 & other international programs, Fiscal Year 2012. Available at: (accessed 5 February 2014)Woodhouse, I.H., Mitchard, E.T.A., Brolly, M., Maniatis, D., Ryan, C.M., Radar backscatter is not a 'direct measure' of forest biomass (2012) Nature Climate Change, 2, pp. 556-557Zanne, A.E., Lopez-Gonzalez, G., Coomes, D.A., Ilic, J., Jansen, S., Lewis, S.L., Miller, R.B., Chave, J., (2009), http://dx.doi.org/10.5061/dryad, Global wood density database. Available at: .234 (accessed 13 June 2013)