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Boosts in Crop Productivity Cause Upswing in Carbon Cycle

Nov 19, 2014 11:07 PM EST

Boosts in crop productivity such as corn reportedly cause an upswing in the carbon dioxide cycle, according to a new study, meaning plants are pulling in more atmospheric carbon as well as releasing more.

The way the cycle works is that each year in the Northern Hemisphere levels of atmospheric carbon dioxide (CO2) drop in the summer as plants "inhale," then climb again as they exhale after the growing season.

Interestingly, for the last 50 years the size of this seasonal swing has increased by as much as half, and researchers are just now beginning to understand why.

According to the results published in the journal Nature, the key is in agricultural production, which may generate up to a quarter of the increase in this seasonal cycle, with an emphasis on corn.

"The fact that this land area can affect the composition of the atmosphere is an amazing fingerprint of human activity on the planet," scientist Mark Friedl of Boston University, the study's senior author, said in a statement.

Scientists gathered global production statistics for four leading crops - corn, wheat, rice and soybeans - that together 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.

"Ecosystems are becoming more productive, pulling in more atmospheric carbon during the summer and releasing more during the dormant period," Friedl explained.

But agriculture isn't the only factor at play here. Warmer temperatures as a result of climate change are also causing this annual change, resulting in longer growing seasons, quicker uptake of carbon by vegetation, and the "greening" of higher latitudes with more vegetation.

However, while some may worry that the increase in these croplands, or "ecosystems on steroids" as some call them, may put the atmosphere in jeopardy of building up more carbon, researchers are reassuring. According to them, the growth in seasonal variation doesn't have a huge impact on global terrestrial carbon uptake and release, since carbon gathered by the crops is released each year.

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