Capitalism and the Nitrogen Cycle

In my previous post, I discussed how the capitalist system has meant changes in the way we utilize the planet. In particular, I explored how the Haber process (a Capitalist invention to maximize food production) has invented industrial agriculture. I also implied that this has also had major impacts on the nitrogen cycle of the Earth. As promised, this post will explore the different consequences of the changes in the nitrogen cycle on the planet, and on us.

To start off, I'll explain what the Nitrogen cycle is.
There are many stages to the nitrogen cycle: nitrogen fixation, nitrification, ammonification, denitrification, and annamox. This is shown in the diagram below.

Source: Nature.com 

 Although nitrogen may be abundant, they are in the form of gas (N2), however they are inaccessible to plants unless they are converted to ammonia. Nitrogen fixation converts N2 into NH3 (Ammonia) through prokaryotes that break the triple bond present in N2. This process is not limited to prokaryotes, as nitrogen fixation can be done abiotically by lightning, or by industrial processes such as fossil fuel combustion. Nitrification occurs after nitrogen fixation, where it converts ammonia into nitrite then nitrate. Anammox refers to the oxidation of ammonia, and are considered an important process in the global nitrogen cycle for the loss of nitrogen in environments such as oceans.

Denitrification, like the name suggests, indicates the process of converting nitrate to nitrogen gas and eventually releasing it into the atmosphere. There are two reactions involved in this process, and can also lead to nitrous oxide (a greenhouse gas!) being released too. Denitrification can be quite threatening to the agricultural industry as the process removes nitrates from fertilizers which can be a costly consequence. Lastly, ammonification is when nitrogen in tissues of organisms decompose and release ammonia into the ecosystem.

Now that we have covered what the nitrogen cycle is, let us look into the implications of the changes we have made in the nitrogen cycle through activities such as agriculture and energy production. The graph below reinstates the point I made in my last post on how much we have changed the enviroment through anthropogenic activities.

Source:Vitousek et al. 1997

One of the biggest impacts of agriculture (in particular, fertilizers) is the resulting algal bloom and eutrophication. The video below summarizes this pretty well.

Source: FuseSchool - Global Education

Eutrophication is a serious issue that affects aquatic ecosystems. It refers to the 'enrichment of surface waters with plant nutrients'. Although this process does happen naturally, it is increasingly associated with anthropogenic activities such as fertilizer run-off, which is referred to as 'cultural eutrophication'. As the video mentioned, fertilizers can seep into aquatic ecosystems through variety of means such as surface run-off into streams and eventually lakes, as well as seeping through groundwater and tainting water quality (rendering it undrinkable.) Products of nitrifcation: NH4, NO3 are water soluble, which make it easy for movement through the soil profile to groundwater by leaching. 

The table below shows the different sources of cultural eutrophication. 

Source: UNEP

As plants are limited in growth by nitrogen and phosphorus, cultural eutrophication encourages the overproduction of aquatic plants and algae. Consequently, agricultural fertilizers and emissions from fossil fuel combustion release nitrogen pollution into these ecosystems. Conversely, phosphoric pollution from wastewater treatment and detergents also seep into these ecosystems, contributing to cultural eutrophication. Whilst phosphorus pollution has been targeted by environmental management strategies which has reduced algal bloom occurrences, it has also meant that nitrogen pollution is passed onto coastal ecosystems, which further drives eutrophication. 

I mentioned earlier that eutrophication can occur naturally, paleoecological investigations into the historical records of eutrophication have shown that they align closely to industrialization, urbanization, and anthropogenic discharge. Similarly, as increased nitrogen emission into the atmosphere is linked to increased deposition of nitrogen on ecosystems, Greenland ice cores have shown an increase in nitrogen isotopes that are linked with industrialization, which was notorious for its use of fossil fuels. Fossil fuels can be seen as nitrogen reserves, and as they are increasingly used, more nitrogen is deposited into the air, and then dissolved into the water which consequently encourages eutrophication.

Increased nitrogen deposition can lead to nitrogen saturation, which negatively impacts soil fertility, which further deter future potential agricultural growth. Additionally, algal blooms lead to reduced dissolved oxygen content in aquatic ecosystems, leading to detrimental impacts on the biological equilibrium which includes fish kills. 

Of course, there are more consequences of anthropogenic impacts on the nitrogen cycle. I'll write about this tomorrow, since I'm finding this quite fascinating.

Before I sign off this post, I wanted to discuss something really quickly. The geographies of Nitrogen distribution should also be considered. For example, whilst there are regions such as Sub-Saharan Africa which experiences little direct input from added nitrogen, other regions such as Northern Europe have had major changes. Personally, I find it interesting that different regions are experiencing different extent of impacts. Additionally, in a world where Nitrogen-based fertilizers are so readily available, I find it rather odd that there are countries where malnutrition and hunger is a regular occurrence. Again, this is the result of not only previous colonial history, but also reflective of the capitalist system.