Nitrogen has key role in estimating CO2 emissions from land use change

News Bureau for the University of Illinois at Urbana-Champaign: A new global-scale modeling study that takes into account nitrogen – a key nutrient for plants – estimates that carbon emissions from human activities on land were 40 percent higher in the 1990s than in studies that did not account for nitrogen.

Researchers at the University of Illinois at Urbana-Champaign and the University of Bristol Cabot Institute published their findings in the journal Global Change Biology. The findings will be a part of the upcoming Fifth Assessment Report from the Intergovernmental Panel on Climate Change.

“One nutrient can make a huge impact on the carbon cycle and net emissions of the greenhouse gas carbon dioxide,” said study leader Atul Jain, a professor of atmospheric sciences at the U. of I. “We know that climate is changing, but the question is how much? To understand that, we have to understand interactive feedback processes – the interactions of climate with the land, but also interactions between nutrients within the land.”

The carbon cycle is a balance of carbon emissions into the atmosphere and absorption by oceans and terrestrial ecosystems. Carbon is absorbed by plants during photosynthesis and by the oceans through sea-air gas exchange. On the other side of the cycle, carbon is released by burning fossil fuels and by changes in land use – deforestation to expand croplands, for example. While fossil fuel emissions are well-known, there are large uncertainties in estimated emissions from land use change.

“When humans disturb the land, the carbon stored in the plants and the soil goes back into the atmosphere,” Jain said. “But when plants regrow, they absorb carbon through photosynthesis. Absorption or release of carbon can be enhanced or dampened depending on environmental conditions, such as climate and nutrient availability.”...

A plowing match in Australia, way back when