When Talking About Climate Change, We Need to Talk About Nitrogen Too

When you hear the word environment in the context of sustainability, you know the word carbon isn’t far off. Given that the release of carbon dioxide and other carbon-based greenhouse gasses through human activity are partly responsible for our changing climate, the connection makes sense. In addition, as the goal of the connection is to promote the protection of our planet – the one safe space we currently have to live in the universe – I’m certainly not against it. 

Protesters against carbon in front of Parliament Canberra. Source: Wikimedia Commons.

However, the problem with focusing on carbon is that the issue of climate change is significantly more complex than just carbon-based greenhouse gasses.

When it comes to the topic of sustainability, I consider myself quite well read and it is one of those topics where I can whip out a bunch of facts and have fairly productive (read: win) debates, despite the fact that no-one actually ever listens to me. As such, it came as quite a shock to me – and somewhat crippled my ego – when I recently found out that there was one facet of the whole issue which I knew almost nothing about: the effect humans are having on the nitrogen cycle. 

You spin me right round

In nature there are a few different cycles key to sustaining life, with the water cycle being probably already quite familiar – how water evaporates from the sea, makes its journey in land, where it then falls as rain and subsequently makes its way back to the oceans.

We also have other important cycles, such as the carbon cycle, which explains how carbon gets trapped in fossils and subsequently fossil fuels; this also explains how man made climate change occurs (we burn these fossil fuels and release the trapped carbon back into the atmosphere). 

A graphic describing the water cycle. Source: Wikimedia Commons.

On top of these there is also the nitrogen cycle, which shows the transfer of nitrogen between ecosystems. Nitrogen is important in the development of life, as major biomolecules such as DNA and proteins contain nitrogen. Around 78% of the atmosphere we live in is composed of nitrogen gas, however this is in a very unreactive form and as such it isn’t accessible to most organisms on the planet.

In nature, the nitrogen gas in the atmosphere is converted into ammonium in a process known as nitrogen fixation, and this is only done by certain types of bacteria & archaea which are single celled organisms called prokaryotes. The ammonium is then converted into nitrite and nitrate ions in a step called nitrification. It is these compounds which can be taken in by plants and the nitrogen can subsequently enter the food chain. Due to the difficulty in fixating nitrogen, this is typically the limiting factor in the growth of plants.

Out of whack

The problem is that the world population was beginning to increase around a century or so ago, and with it the need for more food. While originally invented as a method of making bombs more efficiently, the German (of course) collaborative duo Haber and Bosch managed to design the most efficient industrial method of manufacturing ammonia from atmospheric nitrogen – a vital ingredient in fertilisers – which is still used today.

Since the dawn of this process, the amount of nitrogen fixation has increased significantly, which has had negative consequences on a variety of ecosystems. According to one study, of the amount of fertiliser which is typically applied to crops, around 30-50% will not be absorbed and runs off into waterways. The problem is that once this nitrogen has entered the waterways, it spreads into rivers, lakes and eventually the ocean. This then leads to eutrophication, which is the growth of dense plant life due to nutrient rich waters. When these plants die, the decomposition process uses the oxygen in the water meaning aquatic animals are then suffocated.

An algae bloom due to eutrophication. Source: eutrophication&hypoxia.

In addition, the bacteria in the soil will break down the nitrogen compounds in the fertilisers – as part of the latter steps of the nitrogen cycle – to form nitrous oxide, which is a greenhouse gas. Nitrous oxide has a significantly higher global warming potential than carbon dioxide, with every tonne of nitrous oxide being the equivalent of 298 tonnes of carbon dioxide. Excess nitrogen has also been shown to negatively affect soil fertility by removing essential nutrients like calcium and potassium. 

But don’t we need food?

Though what exactly can we do to prevent such damage to the ecosystem? The human race is expected to continue to grow and there are already people starving in the world. However, given that we waste one third of all the food we produce on a global scale, it becomes quite clear that addressing the problem of nitrogen based pollution lies somewhere in the food system. 

If we were to correctly utilise this one third, we could already reduce the need for nitrogen based fertilisers and as a result the negative outcomes presented above. However, diets which are high in animal products have also been shown to be a completely inefficient use of land: while providing only 18% of calories, these products use 83% of our farmland. Therefore it’s important to talk about the way we deal with food, from what it is we’re eating, to how it is produced and distributed. 

A broader topic

Although the focus in popular climate science has been on the effects of carbon dioxide on our planet, it’s important to accept that the issue never has been, nor will be, as simple as addressing this one point. Any discussion we have about reducing the impact of human activity on the environment must include a frank discussion on our food systems due to the huge impact nitrogen-based pollution has on our environment. 

This issue is one which we don’t need to wait for politicians to talk about in order to tackle, especially in the modern day. In Berlin for example, it’s now easier than ever to find food which is set to be thrown away, for example through the foodsharing community, companies like SIRPLUS* or apps like Too Good To Go. You can also make a conscious effort to eat products which use land more efficiently. In creating a world for the future, it’s important we create a fourth cycle which further supports the other three in sustaining life: a cycle of sustainable human consumption. 

*Disclaimer: At the time of writing, Jack works part time for SIRPLUS.

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Jack McGovan is a recent graduate in chemistry with a specialisation in ‘Energy and Sustainable Chemistry’ from the University of Groningen, the Netherlands. Following a job as a student journalist covering the energy transition, he has moved to Berlin where he is following his passion for working towards creating a fairer and more sustainable world. Seeing a gap in the way in which the world of science was communicated, he founded Delta-S. By writing source based content, he hopes to communicate his findings to a wider audience.