Climate Primer #9: The Eighth Planetary Boundary – The Nitrogen and Phosphorous Cycles

To summarize, climate crisis is the defining issue of the century. Buildup of anthropogenic greenhouse gases in Earth’s atmosphere is driving global heating, while a convergence of global crises threatens to rupture key planetary boundaries (beyond which organized human life on Earth will be threatened) including: stratospheric ozone depletion, biodiversity loss, toxic substance contamination, climate change (the defining sub-category of climate crisis), ocean acidification, freshwater consumption, and land system change.

Today’s post centers – in the framing of the Stockholm Resilience Center, from which the following description is drawn – “Nitrogen and phosphorus flows to the biosphere and oceans”:

The biogeochemical cycles of nitrogen and phosphorus have been radically changed by humans as a result of many industrial and agricultural processes. Nitrogen and phosphorus are both essential elements for plant growth, so fertilizer production and application is the main concern. Human activities now convert more atmospheric nitrogen into reactive forms than all of the Earth’s terrestrial processes combined. Much of this new reactive nitrogen is emitted to the atmosphere in various forms rather than taken up by crops. When it is rained out, it pollutes waterways and coastal zones or accumulates in the terrestrial biosphere. Similarly, a relatively small proportion of phosphorus fertilizers applied to food production systems is taken up by plants; much of the phosphorus mobilized by humans also ends up in aquatic systems. These can become oxygen-starved as bacteria consume the blooms of algae that grow in response to the high nutrient supply. A significant fraction of the applied nitrogen and phosphorus makes its way to the sea, and can push marine and aquatic systems across ecological thresholds of their own. One regional-scale example of this effect is the decline in the shrimp catch in the Gulf of Mexico’s ‘dead zone’ caused by fertilizer transported in rivers from the US Midwest.

This description largely speaks for itself. As with the emission of greenhouse gases, human (again, largely corporate) production and deployment of nitrogen- and phosphorous-containing fertilizers have become so extensive that, beyond adverse local and regional impacts, they have now altered key global “biogeochemical” balances, and are thus, in the process, threatening ecosystem stability at a planetary scale. Not only, then, does industrial agriculture (in particular, the factory farming of non-human animals for human consumption) help drive antibiotic resistance and novel zoonoses, but mechanized, corporate, fossil-fuel- and agri-chemical-dependent agriculture – disproportionately focused, in the US, on the monoculture production of wheat, corn, and soybeans in addition to the raising for slaughter of billions of cows, pigs, and chickens – is a climate, ecological, and health disaster as – to the final point – the pervasiveness of toxic substances like glyphosate and neonicotinoids in our food supplies and bodies attests.