As we look towards 2050, two key trends face the world. One, the population is growing and (for many) becoming wealthier, prompting new nutritional and aspirational demands for food, meat and ultimately protein. Two, climatic change and environmental degradation are reducing our ability to grow food, creating shortages in the most vulnerable parts (and for the most vulnerable peoples) of the world. Standing at the epicentre of these two trends is one element. No, not carbon, but nitrogen, the most abundant element in our atmosphere and essential for all life on earth.
Nitrogen offers the potential to feed our growing population. Over a hundred years ago, in 1909, Fritz Haber discovered how to make ammonia from nitrogen with hydrogen. He invented a fertiliser which has vastly increased agricultural yields and is now estimated to be sustaining one-third of the Earth’s population.
But we now convert more nitrogen from the atmosphere into reactive forms than all of the earth´s terrestrial processes combined, and in disrupting the delicately balanced nitrogen cycle we have placed new pressures on thelife-support systems safeguarding the earth’s future. ‘Fixing’ nitrogen from the atmosphere stimulates plant growth, sequestrating carbon. But it also generates nitrous oxide, which, whilst less abundant in the atmosphere than carbon dioxide, is 298 times more potent in its ability to warm the planet. It is the third largest contributor to global warming. And nitrogen runoff from fertilised fields contaminates groundwater and places new stresses on aquatic ecosystems.
At the core of the problem are two factors. Firstly, we waste too much of the nitrogen we fix. Of the 80m tons of fertiliser spread onto fields each year, only 17m get into food. This is partly because the fertiliser is wastefully applied and partly because modern crops themselves are ‘wasteful’. It is estimated that the nitrogen efficiency of the world’s cereals has fallen from 80% in 1960 to 30% today. Secondly, we consume too much meat-based protein, and therefore too much nitrogen (the building blocks of amino-acids and thus protein). The recommended daily intake of protein is approximately 50g, yet the average American consumes 400g of meat per day. Just as researchers have shown for carbon and water, nitrogen’s footprint exponentially increases as we go up the food chain. So 100g of beef-based protein requires far more nitrogen than 100g of plant-based protein. 33% of the world’s nitrogen budget (based on Rockström planetary boundaries) is used to produce meat for people in the EU, just 7% of the world’s population.
Solutions are available. For example, we might plant more winter cover crops, such as rye or wheat, helping the soil to hold nitrogen. We could reduce our consumption (or at least wastage) of meat-based protein sources. Or we could manipulate plant genes to optimise nitrogen usage (although this brings with it questions of public understanding and acceptance of notions of ‘genetic modification’).
Without nitrogen, a large fraction of people on Earth would not be alive today. Yet if we are to support our future generations sustainably we must decide what price we will pay for the (over-)use of the most abundant element in our atmosphere.
Whilst carbon continues to grab the headlines, is it not time we also turn our attention to nitrogen?
 Wolfe, David W. (2001). Tales from the underground a natural history of subterranean life. Cambridge, Mass: Perseus Pub
 +  Pearce (2009) The Nitrogen Fix:Breaking a Costly Addiction - Environment 360