One doesn’t necessarily think of fashion when they think of the sciences. By fashion I am not talking about the latest lab coat ( I hear white is in), or that must have set of Dior safety glasses, I mean fashion in the sense of the popular trend. Thirty years ago climate change research was just climate research; a more esoteric discipline were theories of an impending ice age were as popular, if not more so, than the idea of global warming. As our ability to measure and compute the parameters that characterize the climate system grew, we came to realise that we had perturbed the carbon cycle at a rate far beyond any point in our Earth’s history. And now, carbon is ‘in’. Who is emitting it? How is it transformed? Can we stuff it back in the sands or just stick our heads there instead? Don’t be mistaken, it is imperative we understand the carbon cycle and how humans have shifted its equilibrium, but it’s not the only elemental cycle out there you know. If you think what we have done to the carbon cycle is bad wait, until you consider the nitrogen cycle. Carbon has been on the catwalk for years now, but this little fashionista predicts you’ll need to make way for nitrogen in your wardrobe very soon.
One could argue that the discovery of the Haber-Bosch process in the early 20th century was a defining moment in our environmental history. While there is an abundance of nitrogen in nature, it is largely found in its unreactive form as N2 gas in air. The Haber-Bosch process enables us to fix nitrogen from air into ammonia and therefore produce the fertilizers that sustain otherwise unsustainable crops. According to a very interesting (albeit quite old) article I happened upon, plants only absorb around 50% of the nitrogen in fertilizers with a meagre 10-15% being consumed by people (which is ultimately returned as sewage). The remaining nitrogen washes into streams, rivers, groundwater and eventually the ocean. Along with the pollution from burning fossil fuels and extensive cultivation of legumes (think soy fillers), we have more than doubled the biologically-available nitrogen pool.
Eutrophication (or an excess of nutrients) can be responsible for harmful algal blooms in our waterways and in our oceans. Oceanic dead zones, or oxygen minimum zones, result from increased bacterial respiration that occurs when such blooms sink. Bacteria metabolize the organic matter, releasing nitrate (NO3) and consuming nearly all available oxygen in the process, making the area uninhabitable for other life forms. According to the article the Gulf of Mexico has a dead zone the size of New Jersey! In these oxygen minimum zones denitrifying bacteria can use the oxygen from nitrate (NO3), releasing the nitrogen back into the atmosphere. When it is released as nitrous oxide (N2O), it can go on to destroy the ozone layer. Now can you see why I need the bio, the geo, and the chemistry in my biogeochemisty PhD.
The nitrogen cycle is complex due to the many forms in which nitrogen can exist. We have much more to learn about the natural nitrogen cycle before we can fully understand the flow on effects of current perturbation. With all eyes on last weeks Conference on Sustainable development in Rio (and our Sarlae who happened to be there), discussion of how to manage our ‘nitrogen footprint’ should have been as important as our ‘carbon footprint’. And if you thought the latter was contentious, the nitrogen cycle is fundamental to food production…… any one brave enough to suggest how else to feed 7 billion people?