#FactsMatter | Headlines warn that our soil is becoming so degraded that we are heading for an agricultural Armageddon. Can that be right?

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WHEN it comes to science reporting, there are some headlines that are so frequently repeated, so intuitively plausible, so closely aligned to our cultural beliefs, that they can seem like incontrovertible truths.

The general public, and indeed many scientists, may fervently believe that these claims reflect the overwhelming scientific consensus. However, sometimes when you dig a little beyond the surface, the evidence underpinning even the most ubiquitous headlines can seem surprisingly shaky.

Perhaps the best example of such an assertion is that of an impending agricultural Armageddon, caused by decades of irresponsible farming practices that have degraded soils across the planet (or so the press narrative goes).

A quick scan of the headlines reveals that despite the confidence with which these forecasts are proclaimed, the actual timescale to D-Day varies rather widely from story to story. While some report that we have 100 years until the end of our soil’s ability to support farming, citing a University of Sheffield study, others claim that this is a mere 60 years away, referencing a speech at the UN’s Food and Agriculture Organization.

Recently, the UK government’s environment secretary even stated that the UK is as little as 30 years away from an “eradication of soil fertility” because we “drench it in chemicals”. If this is indeed a likely end-game scenario, we should probably determine which of these estimates is most plausible as a matter of urgency: 30, 60 or 100 years. So let’s take a closer look at this claim.

Despite dozens of headlines quoting these predictions, surprisingly only one peer-reviewed paper from a scientific journal is ever cited as evidence to back them up. This 2014 study from the University of Sheffield compared the soil quality of a range of sites in the English city, including agricultural, garden and allotment soils.

Now, before we question whether the results of this single, small study can be extrapolated to represent all of England, let alone the whole UK or even the whole world, let us take a look at their findings: basically, some urban soils in Sheffield are higher in carbon and nitrogen than some nearby agricultural ones. OK, but where is the 100-year statistic? It turns out that nowhere in the study was there any calculation, prediction or even passing reference to the claim. None whatsoever. Perhaps not so much shaky evidence to support this assertion as much as non-existent.

“I asked leading soil scientists if they had ever come across such a prediction in published research. Not a single one had”

Maybe this is the result of a typo and the work is in another research paper? After an 8-hour trawl through the academic journals failed to pull up a single study that even attempted to make this calculation, I contacted six leading soil scientists across the world to ask if they had ever come across such a prediction in either the published literature or their work. Not a single one had.

In fact, the words they used to describe this claim were “bold”, “too Malthusian”, “hardly useful”, “almost insulting” and “I have used this in my soil science lectures to show the students to be wary of headlines!”. Ouch.

Does that mean there aren’t real threats to some agricultural soils around the world? Absolutely not. Indeed, all the scientists I spoke to went to great lengths to point these out, where they exist.

However, they also highlighted how incredibly complex the calculations needed to make such predictions would be, based on myriad factors, only some of which can be predicted with any reliability, with generalisations almost impossible. The boring reality is that while soils in some parts of the world might be in decline, others are not.

Furthermore, while agriculture may be one of the factors driving erosion and nutrient depletion, many modern farming practices such as no-till and synthetic fertiliser applications may actually be helping alleviate (rather than drive) this. In fact, according to many objective measures, modern, evidence-based farming techniques are more sustainable than those of an idealised past. Quite a different picture to that painted by the headlines.

Despite the thirst for simple truths in a complicated world, the researchers I contacted agreed that setting such a figure for an agricultural “end-point” would be nigh on impossible, which may explain why no published studies appear to have been able to do so. But this hasn’t stopped the newspapers. Welcome to 2019!

James Wong is a botanist and science writer, with a particular interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew, he shares his tiny London flat with more than 500 houseplants. You can follow him on Twitter and Instagram @botanygeek

James’s week What are you reading? A lot of very dry, academic journals, mainly. What are you watching? Kim’s Convenience on Netflix (while reading the dry, academic journals). What are you working on? Prepping a series of talks, promoting a book, working on a radio show and writing a shiny new column for an amazing science magazine.

This column will appear monthly. Up next week: theoretical physicist Chanda Prescod-Weinstein