Washington, Nov 20 (IANS): A sharp rise in food production to meet the demands for rising population accounts for as much as 25 percent of the seasonal increase in carbon dioxide (CO2), finds new research.

The carbon dioxide absorbed by plants in the spring and summer as they convert solar energy into food is released back to the atmosphere in autumn and winter.

It is not that crops are adding more CO2 to the atmosphere; rather, if crops are like a sponge for CO2, the sponge has simply gotten bigger and can hold and release more of the gas, the study noted.

"This is another piece of evidence suggesting that when we (humans) do things at a large scale, we have the ability to greatly influence the composition of the atmosphere," said co-author of the study Chris Kucharik from University of Wisconsin-Madison in the US.

With global food productivity expected to double over the next 50 years, the findings should be used to improve climate models and better understand the atmospheric CO2 buffering capacity of ecosystems, the researchers pointed out.

"Global climate models do not represent the important details of agro-ecosystems and their management very well," Kucharik added.

The study found that, while the area of farmed land has not significantly increased, the production efficiency of that land has. Intensive agricultural management over the last 50 years has had a profound impact.

Kucharik attributes this to improvements in plant breeding, post-World War II fertilization innovations, irrigation and other human-powered technologies.

The study appeared in the journal Nature.