A World Awash with Nitrogen

In "A World Awash in Nitrogen," Elser, the author, writes that humans, like all species, long operated within the constraints of the natural nitrogen cycle. In early agricultural periods, humans returned animal and human wastes to the fields, thereby adding nitrogen (and phosphorus) and enhancing crop productivity. The industrial age brought this era to a close via two innovations: artificial nitrogen fixation and the internal combustion engine.

The studies that Elser reviews show that the impacts of nitrogen fertilisation have now affected all parts of the world, from temperate to tropical regions, and from forests to the oceans. Else concludes that this flurry of discoveries about the spreading extent of humankind’s unintentional nitrogen experiment should add urgency to recent concerns about the multidimensional planetary boundaries that humanity is pressuring. It adds weight to speculation that the biosphere is heading toward a widespread condition of chronic phosphorus limitation. Whether these effects signal a an ephemeral blip in the stratigraphic record or a sustained shift lasting millennia may, in due time, be seen as an indicator of humanity’s success, or failure, in achieving planetary sustainability.
 

Reference

Elser J J (2011) A World Awash with Nitrogen. Science; 334 (6062). 

It can be downloaded (subscription needed) here:  1504 DOI: 10.1126/science.1215567
 
One of the main studies that the Elser piece refers to is:

Holtgrieve G W, Schindler D E, Hobbs W O, Leavitt P R, Ward E J, Bunting L, Chen G, Finney B , Gregory-Eaves I, Holmgren S, Lisac M J, Lisi P J, Nydick K, Rogers L A, Saros J E, Selbie D T, Shapley M D, Walsh P B, Wolfe A P. (2011). A Coherent Signature of Anthropogenic Nitrogen Deposition to Remote Watersheds of the Northern Hemisphere, Science, 334 6062 pp. 1545-1548 and can be downloaded here.
 
You can also read coverage in Science Daily here.