1 Tahrcountry Musings: Depredations caused by human nitrogen additions

Tuesday, September 06, 2011

Depredations caused by human nitrogen additions

Latest research has come up with the finding that human nitrogen additions to terrestrial ecosystems increase the terrestrial carbon dioxide uptake from the atmosphere. Nitrogen inputs to biosphere have more than doubled since the 1860s.  Fossil fuel burning and the application of fertilizers in agriculture are the villains.

When added to nitrogen-limited ecosystems, more nitrogen inputs can stimulate plant growth and/or suppress soil respiration. This in turn leads to increased ecosystem carbon storage.

The researchers used a process-based model of the terrestrial biosphere to evaluate the overall impact of anthropogenic nitrogen inputs on terrestrial ecosystem carbon and nitrous oxide fluxes between 1700 and 2005. They show that anthropogenic nitrogen inputs account for about a fifth of the carbon sequestered by terrestrial ecosystems between 1996 and 2005, and for most of the increase in global nitrous oxide emissions in recent decades. Nitrous oxide emissions   are largely due to intensive agricultural practices. The researchers estimate that carbon sequestration due to nitrogen deposition has reduced current carbon dioxide radiative forcing by 96±14mWm−2. However, this effect has been offset by the increase in radiative forcing resulting from nitrous oxide emissions, which amounts to 125±20mWm−2.

Journal Reference:
Sönke Zaehle, Philippe Ciais, Andrew D. Friend, Vincent Prieur. Carbon benefits of anthropogenic reactive nitrogen offset by nitrous oxide emissions. Nature Geoscience

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