MINNEAPOLIS / ST. PAUL (11/19/14) The application of a recently developed crop statistics database at the University of Minnesota’s Institute on the Environment in conjunction with a carbon accounting model developed at Boston University has shown that intensified agricultural production in the northern hemisphere is generating up to a quarter of increased atmospheric carbon dioxide seasonality, reports a paper published in the November 5 issue of the journal Nature.
Deepak Ray, research associate at IonE’s Global Landscapes Initiative, who led the development of the dataset and contributed to this study, said, “This is the perfect example of assembling a multidisciplinary, multi-institutional team of experts tackling an intractable problem of why the atmospheric carbon dioxide seasonality is intensifying.”
Each year in the northern hemisphere, levels of atmospheric carbon dioxide drop in the summer as plants inhale (absorb it for photosynthesis), and then climb again after their growing season. Over the past 50 years, the size of this seasonal swing has increased by as much as half, for reasons that aren’t fully understood. “Most of the explanations put forward to date involve climate warming, particularly at high latitudes, a longer growing season and enhanced photosynthetic activity, and greater plant productivity due to increasing atmospheric CO2,” says study co-author Steve Frolking of the University of New Hampshire.
The multidisciplinary team of researchers led by Boston University scientists has shown that agricultural production may generate up to a quarter of the increase in this seasonal carbon cycle, with corn playing a leading role. GLI’s crop database allowed the scientists to find that production of four leading crops — corn, wheat, rice and soybeans — that represent about 64 percent of all calories consumed worldwide in the northern hemisphere above the tropics has more than doubled since 1961, and after accounting for the carbon translates to about a billion metric tons of carbon captured and released each year.
These croplands are “ecosystems on steroids,” says Josh Gray, BU research assistant professor and lead author on the paper, noting that they occupy about 6 percent of the vegetative land area in the northern hemisphere but are responsible for up to a quarter of the total increase in seasonal carbon exchange of atmospheric CO2. “The fact that such a small land area can actually affect the composition of the atmosphere is an amazing fingerprint of human activity on the planet,” notes Mark Friedl, a professor in Boston University’s department of Earth and environment and senior author of the paper.
While increased crop production does not have much impact on the long-term increase of CO2 in the atmosphere, understanding the effects of agricultural production, the researchers say, will help to improve models of global climate, which currently do not represent agricultural management very well.
The paper, titled “Direct human influence on atmospheric CO2 seasonality from increased cropland productivity” can be viewed online at the journal Nature.
The research team includes lead authors Mark Friedl and Josh Gray of Boston University; Eric Kort, University of Michigan in Ann Arbor; Steve Frolking, University of New Hampshire at Durham; Christopher Kucharik, University of Wisconsin at Madison; Navin Ramankutty, then at McGill University and now at the University of British Columbia at Vancouver; and Deepak Ray of the University of Minnesota Institute on the Environment.
The research was funded primarily though programs supported by the National Science Foundation and National Aeronautics and Space Administration. Deepak Ray was supported by the Gordon and Betty Moore Foundation and IonE.
Photo by James Clear (Flickr/Creative Commons)