Nov 21, 2014 by Sci-News.com
Crop production may generate up to a quarter of the increase in the seasonal cycle of atmospheric carbon dioxide, with corn playing a leading role, according to a new study published in the journal Nature.
Intensification of agriculture is a driver of changes in the seasonal characteristics of the global carbon cycle.
Each year in the Northern Hemisphere, levels of atmospheric carbon dioxide drop in the summer as plants inhale, and then climb again as they exhale and decompose after their growing season.
Over the past five decades, the size of this seasonal swing has increased by as much as half, for reasons that aren’t fully understood.
“In the Northern Hemisphere, there is a strong seasonal cycle of vegetation. Something is changing about this cycle; the ecosystems are becoming more productive, pulling in more atmospheric carbon during the summer and releasing more during the dormant period,” said study senior author Prof Mark Friedl of Boston University.
Prof Friedl and his colleagues gathered global production statistics for four leading crops – corn, wheat, rice and soybeans – that represent about 64 percent of all calories consumed worldwide.
They found that production of these crops in the Northern Hemisphere has more than doubled since 1961, and translates to about a billion metric tons of carbon captured and released each year.
“These croplands are ecosystems on steroids. They occupy about 6 percent of the vegetated land area in the Northern Hemisphere but are responsible for up to a quarter of the total increase in seasonal carbon exchange of atmospheric carbon dioxide, and possibly more,” said lead author Dr Josh Gray of Boston University.
“That’s a very large, significant contribution, and 2/3 of that contribution is attributed to corn. Corn once again is king, this time demonstrating its strong influence on the seasonal cycle of atmospheric carbon dioxide,” said study co-author Prof Christopher Kucharik of the University of Wisconsin-Madison.
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