Direct human influence on atmospheric CO 2 seasonality from increased cropland productivity

Josh M. Gray, Steve Frolking, Eric A. Kort, Deepak K. Ray, Christopher J. Kucharik, Navin Ramankutty, Mark A. Friedl

Research output: Contribution to journalArticle

63 Scopus citations

Abstract

Ground- and aircraft-based measurements show that the seasonal amplitude of Northern Hemisphere atmospheric carbon dioxide (CO 2) concentrations has increased by as much as 50 per cent over the past 50 years. 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 vegetation. However, the precise causal mechanisms behind the observed changes in atmospheric CO 2 seasonality remain unclear. 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 CO 2 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.

Original languageEnglish (US)
Pages (from-to)398-401
Number of pages4
JournalNature
Volume515
Issue number7527
DOIs
StatePublished - Nov 20 2014

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    Gray, J. M., Frolking, S., Kort, E. A., Ray, D. K., Kucharik, C. J., Ramankutty, N., & Friedl, M. A. (2014). Direct human influence on atmospheric CO 2 seasonality from increased cropland productivity. Nature, 515(7527), 398-401. https://doi.org/10.1038/nature13957