Tipping towards the unknown

- The human pressure on the Earth System has reached a scale where abrupt global environmental change can no longer be excluded. To continue to live and operate safely, humanity has to stay away from critical ‘hard-wired´ thresholds in Earth´s environment, and respect the nature of planet's climatic, geophysical, atmospheric and ecological processes, says Johan Rockström, Director of the Stockholm Resilience Centre. A group of 28 internationally renowned scientists propose that global biophysical boundaries, identified on the basis of the scientific understanding of the Earth System, can define a ‘safe planetary operating space´ that will allow humanity to continue to develop and thrive for generations to come. Read more about it on "Tipping towards the unknown"

I could not agree more. Thes girls and guys have identified nine critical boundaries, of which at least six are elaborated upon in depth in my Garden Earth book. I believe the disturbances in the Nitrogen cycle is likely to be one of the most critical issues.

The scientist write:
"Nitrogen and phosphorus inputs to the biosphere and oceans
Human modification of the nitrogen cycle has been even greater than our modification of the carbon cycle. Human activities now convert more N2 from the atmosphere into reactive forms than all of the Earth´s terrestrial processes combined. Much of this new reactive nitrogen pollutes waterways and coastal zones, is emitted to the atmosphere in various forms, or accumulates in the terrestrial biosphere. A relatively small proportion of the fertilizers applied to food production systems is taken up by plants. A significant fraction of the applied nitrogen and phosphorus makes its way to the sea, and can push marine and aquatic systems across thresholds of their own. A concrete example of this effect is the decline in the shrimp catch in the Gulf of Mexico due to hypoxia caused by fertilizer transported in rivers from the US Midwest."