Letter | Published:

Direct human influence on atmospheric CO2 seasonality from increased cropland productivity

Nature volume 515, pages 398401 (20 November 2014) | Download Citation


Ground- and aircraft-based measurements show that the seasonal amplitude of Northern Hemisphere atmospheric carbon dioxide (CO2) concentrations has increased by as much as 50 per cent over the past 50 years1,2,3. This increase has been linked to changes in temperate, boreal and arctic ecosystem properties and processes such as enhanced photosynthesis, increased heterotrophic respiration, and expansion of woody vegetation4,5,6. However, the precise causal mechanisms behind the observed changes in atmospheric CO2 seasonality remain unclear2,3,4. Here we use production statistics and a carbon accounting model to show that increases in agricultural productivity, which have been largely overlooked in previous investigations, explain as much as a quarter of the observed changes in atmospheric CO2 seasonality. Specifically, Northern Hemisphere extratropical maize, wheat, rice, and soybean production grew by 240 per cent between 1961 and 2008, thereby increasing the amount of net carbon uptake by croplands during the Northern Hemisphere growing season by 0.33 petagrams. Maize alone accounts for two-thirds of this change, owing mostly to agricultural intensification within concentrated production zones in the midwestern United States and northern China. Maize, wheat, rice, and soybeans account for about 68 per cent of extratropical dry biomass production, so it is likely that the total impact of increased agricultural production exceeds the amount quantified here.

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  1. 1.

    , & Increased activity of northern vegetation inferred from atmospheric CO2 measurements. Nature 382, 146–149 (1996)

  2. 2.

    , , , & The contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric carbon dioxide. Glob. Biogeochem. Cycles 11, 535–560 (1997)

  3. 3.

    et al. Enhanced seasonal exchange of CO2 by northern ecosystems since 1960. Science 341, 1085–1089 (2013)

  4. 4.

    et al. Net carbon dioxide losses of northern ecosystems in response to autumn warming. Nature 451, 49–52 (2008)

  5. 5.

    et al. Plot-scale evidence of tundra vegetation change and links to recent summer warming. Nature Clim. Change 2, 453–457 (2012)

  6. 6.

    et al. Large-scale variations in the vegetation growing season and annual cycle of atmospheric CO2 at high northern latitudes from 1950 to 2011. Glob. Change Biol. 19, 3167–3183 (2013)

  7. 7.

    , & Seasonal amplitude increase in atmospheric CO2 concentration at Mauna Loa, Hawaii, 1959–1982. J. Geophys. Res. D 90, 10529–10540 (1985)

  8. 8.

    & The annual variation of atmospheric CO2 concentration observed in the Northern Hemisphere. J. Geophys. Res. Oceans 86, 9839–9843 (1981)

  9. 9.

    et al. Temperature and vegetation seasonality diminishment over northern lands. Nature Clim. Change 3, 581–586 (2013)

  10. 10.

    et al. Seasonality of ecosystem respiration and gross primary production as derived from FluxNET measurements. Agric. For. Meteorol. 113, 53–74 (2002)

  11. 11.

    FAO. FAOSTAT Database (Food and Agriculture Organization of the United Nations, 2013)

  12. 12.

    , , & Global food demand and the sustainable intensification of agriculture. Proc. Natl Acad. Sci. USA 108, 20260–20264 (2011)

  13. 13.

    , , , & Recent patterns of crop yield growth and stagnation. Nature Commun. 3, 1293 (2012)

  14. 14.

    Contribution of planting date trends to increased maize yields in the central United States. Agron. J. 100, 328–336 (2008)

  15. 15.

    et al. Closing yield gaps through nutrient and water management. Nature 490, 254–257 (2012)

  16. 16.

    , & Climate change and food systems. Annu. Rev. Environ. Resour. 37, 195–222 (2012)

  17. 17.

    & Net carbon flux from agriculture: carbon emissions, carbon sequestration, crop yield, and land-use change. Biogeochemistry 63, 73–83 (2003)

  18. 18.

    & A synthesis of carbon sequestration, carbon emissions, and net carbon flux in agriculture: comparing tillage practices in the United States. Agric. Ecosyst. Environ. 91, 217–232 (2002)

  19. 19.

    et al. Atmospheric carbon dioxide variability in the community earth system model: evaluation and transient dynamics during the twentieth and twenty-first centuries. J. Clim. 26, 4447–4475 (2013)

  20. 20.

    et al. Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence. Proc. Natl Acad. Sci. 111, E1327–E1333 (2014)

  21. 21.

    et al. Climate-driven increases in global terrestrial net primary production from 1982 to 1999. Science 300, 1560–1563 (2003)

  22. 22.

    et al. Role of land-surface changes in Arctic summer warming. Science 310, 657–660 (2005)

  23. 23.

    , , & Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance. Proc. Natl Acad. Sci. USA 102, 13521–13525 (2005)

  24. 24.

    et al. Carbon balance of the terrestrial biosphere in the twentieth century: analyses of CO2, climate and land use effects with four process-based ecosystem models. Glob. Biogeochem. Cycles 15, 183–206 (2001)

  25. 25.

    et al. The changing carbon cycle at Mauna Loa observatory. Proc. Natl Acad. Sci. USA 104, 4249–4254 (2007)

  26. 26.

    et al. Drier summers cancel out the CO2 uptake enhancement induced by warmer springs. Proc. Natl Acad. Sci. USA 102, 10823–10827 (2005)

  27. 27.

    et al. Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2. Science 316, 1732–1735 (2007)

  28. 28.

    et al. A large and persistent carbon sink in the world’s forests. Science 333, 988–993 (2011)

  29. 29.

    et al. The global carbon budget 1959–2011. Earth Syst. Sci. Data Discuss. 5, 1107–1157 (2012)

  30. 30.

    et al. Solutions for a cultivated planet. Nature 478, 337–342 (2011)

  31. 31.

    , , , & Regional uptake and release of crop carbon in the United States. Biogeosciences 8, 2037–2046 (2011)

  32. 32.

    , , , & Net primary production of US midwest croplands from agricultural harvest yield data. Ecol. Appl. 11, 1194–1205 (2001)

  33. 33.

    et al. Satellite estimates of productivity and light use efficiency in united states agriculture, 1982-98. Glob. Change Biol. 8, 722–735 (2002)

  34. 34.

    Harvest index—a review of its use in plant-breeding and crop physiology. Ann. Appl. Biol. 126, 197–216 (1995)

  35. 35.

    Historical changes in harvest index and crop nitrogen accumulation. Crop Sci. 38, 638–643 (1998)

  36. 36.

    , & Genetic improvement in short season soybeans: I. dry matter accumulation, partitioning, and leaf area duration. Crop Sci. 41, 391–398 (2001)

  37. 37.

    Efficiencies and biomass appropriation of food commodities on global and regional levels. Agric. Syst. 77, 219–255 (2003)

  38. 38.

    , , & Physiological processes associated with wheat yield progress in the UK. Crop Sci. 45, 175–185 (2005)

  39. 39.

    , & Estimating source carbon from crop residues, roots and rhizodeposits using the national grain-yield database. Agron. J. 98, 622–636 (2006)

  40. 40.

    et al. Quantifying and mapping the human appropriation of net primary production in earth’s terrestrial ecosystems. Proc. Natl Acad. Sci. USA 104, 12942–12947 (2007)

  41. 41.

    , , & Breeding maize for a bioeconomy: a literature survey examining harvest index and stover yield and their relationship to grain yield. Crop Sci. 50, 1–12 (2010)

  42. 42.

    , , & Effect of lowering the root/shoot ratio by pruning roots on water use efficiency and grain yield of winter wheat. Field Crops Res. 115, 158–164 (2010)

  43. 43.

    & Crop management techniques to enhance harvest index in rice. J. Exp. Bot. 61, 3177–3189 (2010)

  44. 44.

    , & Direct and indirect estimation of leaf area index, fAPAR, and net primary production of terrestrial ecosystems. Remote Sens. Environ. 70, 29–51 (1999)

  45. 45.

    , , & Nitrogen supply affects root: shoot ratio in corn and velvetleaf (Abutilon theophrasti). Weed Sci. 53, 670–675 (2005)

  46. 46.

    , , & Morphological and physiological responses of rice (Oryza sativa) to limited phosphorus supply in aerated and stagnant solution culture. Ann. Bot. 98, 995–1004 (2006)

  47. 47.

    , , & Effects of increased ammonia on root/shoot ratio, grain yield and nitrogen use efficiency of two wheat varieties with various N supply. Plant Soil Environ. 55, 273–280 (2009)

  48. 48.

    , , & Effects of soil temperature on growth and root function in rice. Plant Prod. Sci. 13, 235–242 (2010)

  49. 49.

    et al. Ecological intensification of rice production in the lowlands of Amazonia—options for smallholder rice producers. Eur. J. Agron. 46, 25–33 (2013)

  50. 50.

    et al. Root:shoot ratios and belowground biomass distribution for pacific northwest dryland crops. J. Soil Water Conserv. 68, 349–360 (2013)

  51. 51.

    FluxNET. (2014)

  52. 52.

    et al. Carbon sequestration by a crop over a 4-year sugar beet/winter wheat/seed potato/winter wheat rotation cycle. Agric. For. Meteorol. 149, 407–418 (2009)

  53. 53.

    , & Trends in rice-wheat area in China. Field Crops Res. 87, 89–95 (2004)

  54. 54.

    , , & Crop planting dates: an analysis of global patterns. Glob. Ecol. Biogeogr. 19, 607–620 (2010)

  55. 55.

    The role of carbohydrate storage and redistribution in the source-sink relations of wheat and barley during grain filling—a review. New Phytol. 123, 233–245 (1993)

  56. 56.

    et al. Combining remote sensing and ground census data to develop new maps of the distribution of rice agriculture in China. Glob. Biogeochem. Cycles 16, 1091 (2002)

  57. 57.

    et al. Mapping single-, double-, and triple-crop agriculture in China at 0.5x0.5 by combining county-scale census data with remote sensing-derived land cover map. Geocarto Int. 18, 3–13 (2003)

  58. 58.

    , , & Tillage and soil carbon sequestration—what do we really know? Agric. Ecosyst. Environ. 118, 1–5 (2007)

  59. 59.

    , , , & Combining satellite data and biogeochemical models to estimate global effects of human-induced land cover change on carbon emissions and primary productivity. Glob. Biogeochem. Cycles 13, 803–815 (1999)

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This work used eddy covariance data acquired by the FLUXNET community and in particular by the following networks: AmeriFlux (US Department of Energy, Biological and Environmental Research, Terrestrial Carbon Program (DE-FG02-04ER63917 and DE-FG02-04ER63911)), AfriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, CarboItaly, CarboMont, ChinaFlux, Fluxnet-Canada (supported by CFCAS, NSERC, BIOCAP, Environment Canada, and NRCan), GreenGrass, KoFlux, LBA, NECC, OzFlux, TCOS-Siberia, USCCC. We acknowledge the financial support to the eddy covariance data harmonization provided by CarboEuropeIP, FAO-GTOS-TCO, iLEAPS, Max Planck Institute for Biogeochemistry, National Science Foundation, University of Tuscia, Université Laval and Environment Canada and US Department of Energy and the database development and technical support from Berkeley Water Center, Lawrence Berkeley National Laboratory, Microsoft Research eScience, Oak Ridge National Laboratory, University of California - Berkeley, University of Virginia. This work was supported by NASA grant number NNX11AE75G and NSF grant numbers EF-1064614 and NSF EAR-1038818. Research support to D.K.R. was primarily provided by the Gordon and Betty Moore Foundation and the Institute on Environment at the University of Minnesota. We also acknowledge input and data provided by H. Graven and P. Patra.

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Author notes

    • Navin Ramankutty

    Present address: Liu Institute for Global Issues and Institute for Resources, Environment, and Sustainability, University of British Columbia, Vancouver, British Columbia V6T 1Z2, Canada.


  1. Department of Earth and Environment, Boston University, Boston, Massachussetts 02215, USA

    • Josh M. Gray
    •  & Mark A. Friedl
  2. Earth Systems Research Center, University of New Hampshire, Durham, New Hampshire 03824, USA

    • Steve Frolking
  3. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA

    • Eric A. Kort
  4. Institute on the Environment, University of Minnesota, Saint Paul, Minnesota 55108, USA

    • Deepak K. Ray
  5. Department of Agronomy and Nelson Institute Center for Sustainability and the Global Environment, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

    • Christopher J. Kucharik
  6. Department of Geography, McGill University, Montreal, Quebec H3A 0B9, Canada

    • Navin Ramankutty


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J.M.G. led the design, analysis, and writing of the paper. J.M.G., S.F., N.R. and M.A.F. designed the analysis. E.A.K. provided the initial inspiration for the paper and guidance on interpreting atmospheric CO2 dynamics. C.J.K. contributed guidance on agronomic elements of the paper. D.K.R. provided the gridded MWRS data set. All authors edited and contributed to writing the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Josh M. Gray.

MWRS yield and harvested area data will be archived at http://www.earthstat.org and are available on request.

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