Climate Change: New Forests Don't Store As Much Carbon as Previously Thought

Forests are often planted to help with carbon capture and storage. But exactly how effective are these trees at keeping carbon? Scientists have found that predictions for carbon storage may just be overestimated.

In this latest study, the researchers modeled future land cover and land use changes and other factors. While many forests will absorb carbon dioxide, they'll be limited as to how much they can absorb due to a shortage of nitrogen.

"Forests take up carbon from the atmosphere, but in order for the plants to fix the carbon, it requires a certain amount of nitrogen," said Prasanth Meiyappan, one of the researchers, in a news release. "If that ratio of carbon to nitrogen isn't right, even if you add many times more carbon than it gets currently, the forests cannot absorb the extra carbon."

Most forested land on Earth is actually secondary forest. When the original forested land is disturbed, much of the nitrogen that is in the soil is released into the atmosphere, making growth in these areas relatively slow. In addition, plant matter is often removed from areas for burning, this means that the nitrogen is limited even further.

The Intergovernmental Panel on Climate Change has projected that bioenergy will be needed to meet an anticipated dramatic increase in the world's energy consumption while still limiting carbon dioxide emissions. Forest products and residues and an increase in the range of timber-harvested forests will be a large factor in meeting these energy demands.

"We hope this study will trigger a discussion on the importance for climate models to consider nitrogen limitation when evaluating the strength of future land carbon uptake, for the next IPCC report," said Meiyappan.

The findings are published in the journal Global Biogechemical Cycles.

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