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THE interconnectivity of our world never fails to amaze me. Even as a plant scientist fascinated by food production, I am often astonished by the extent to which changes in a seemingly unrelated industry on a distant part of the planet can affect our dinner plates – and the reaction of pundits to these impacts.

Recently, news broke that soaring global fertiliser costs, created by factors such as rising energy prices in China, would be likely to have a devastating knock-on effect on the food security of some of the poorest people on Earth.

Surprisingly, some activists and thought leaders saw this price hike as a good thing, because it would provide a market mechanism to force farmers to reduce their “addiction” to fertilisers. According to this narrative, fertiliser use has gone “up and up”, and masked a “terrifying and accelerating” collapse in global soil health, which is often worse for people in low-income countries trying to feed themselves. Given the frequency and conviction with which this view is expressed, and the devastating impact it could have, I thought I should go in search of the facts.

So, the first thing we need to acknowledge is that overuse of fertiliser is a problem. It is well established that run-off of excess nutrients pollutes water courses, with a destructive impact on the environment. The extent of this effect can be wide-ranging, with farmland run-off in the US Midwest contributing to algal blooms in the Gulf of Mexico hundreds, , of kilometres away.

That is before we talk about the greenhouse gas emissions produced in the manufacture of fertiliser. Alone, the Haber-Bosch process – which captures atmospheric nitrogen and converts it into a soluble form that plants can more readily use – produces roughly . That might sound like a small amount until you compare it with the emissions associated with all of the aviation industry, which are .

I think we can all agree that reducing our reliance on such synthetic fertilisers would be a good thing. But this is where it starts to get complicated. Despite frequent reports of ever-escalating use of synthetic fertiliser, in fact, in many Western countries, it has markedly declined.

In the UK, for example, the amount of fertiliser used per hectare has fallen by about 20 per cent since the turn of the millennium, and is now at its . Many other European countries, including the Netherlands, Italy and Denmark, have seen a similar trajectory, as has Japan. Even when you include some of the world’s most important food-producing countries such as the US, Russia and Australia, you see a plateauing of fertiliser use over the past two decades, certainly not the unstoppable upwards trajectory that is often claimed.

“In the UK, the amount of fertiliser used per hectare has fallen by about 20 per cent since the millennium”

What is true, however, is that on a global level, there has been a big increase in the use of fertilisers in the same period, with a .

Even this, though, doesn’t really show us the complete picture. Fertiliser usage is traditionally calculated by the weight used per unit of land. Given that the whole point of the exercise is to feed people, would it not make more sense to see these stats in the context of global population levels? After all, while global land area hasn’t changed in the past two decades, our population has increased by around 27 per cent.

Use of synthetic fertiliser broadly reflects an increase in the number of mouths to feed. In fact, some scientists have calculated that since its widespread adoption at the beginning of the 20th century, it has been the only way we have been able to support a growing population. Two decades ago, these fertilisers allowed us to feed . By 2015, that figure was estimated to have increased to just under half the world’s population.

Here is some more context: today, as many as . In fact, after decades of progress, the number of people lacking access to sufficient food is on the rise again, growing by as many as 161 million between 2019 and 2020 alone. Severe food insecurity now affects just under .

So, yes, we do need to reduce our reliance on fertiliser use, and many of the world’s advanced economies have already taken great strides to do that. However, there is no solid evidence to support the claim that fertiliser use is dramatically rising, particularly in the context of countries like the UK. And, crucially, taking into account the human cost, the argument that fertiliser price rises are in some way beneficial to humanity is one that can be made only with the luxury of a full belly.