According to this 2014 Scientific American article by Chris Arsenault

Generating three centimeters of top soil takes 1,000 years, and if current rates of degradation continue all of the world's top soil could be gone within 60 years, a senior UN official said on Friday.

About a third of the world's soil has already been degraded, Maria-Helena Semedo of the Food and Agriculture Organization (FAO) told a forum marking World Soil Day.

I haven't found a transcript of Semedo's speech, or any basis for her statement. I find it curious that such a dire statement supposedly made by a credible authority is not much more widely supported on the web.

Is the world's top soil predicted to be gone in 60 years, according to scientists?

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    @KamilDrakari: I focussed on the latter - if people believe it is true, it doesn't matter if Semedo said it or not. – Oddthinking Jan 23 at 15:07
  • @Oddthinking That's fair, I didn't realize the linked article contained enough information. The current form seems fine to me. – Kamil Drakari Jan 23 at 15:11
  • I've heard such claims before, so @odd's edit is the one that makes sense. – fredsbend Jan 23 at 15:13
  • This is a media story to generate interest/ fill a newspaper. If taken literallyit would mean the cornbelt in the US that has produced corn for over 200 years in some locations and produces more corn per acre every decade is "fake" news ? – blacksmith37 Jan 23 at 15:55
  • @blacksmith37 Actually Semedo's comment supports your assertion. The increasing demand on soils owing to modern agriculture, particularly the mechanization and use of fertilizers that lead to the increasing yields you speak of, is central to the problem being discussed. – WetSavannaAnimal Jan 23 at 23:16

If she said it in 2014, she wasn't the first.

For example, in a 2012 interview, Professor John Crawford of the University of Sydney said ,

A rough calculation of current rates of soil degradation suggests we have about 60 years of topsoil left. Some 40% of soil used for agriculture around the world is classed as either degraded or seriously degraded – the latter means that 70% of the topsoil, the layer allowing plants to grow, is gone. Because of various farming methods that strip the soil of carbon and make it less robust as well as weaker in nutrients, soil is being lost at between 10 and 40 times the rate at which it can be naturally replenished. Even the well-maintained farming land in Europe, which may look idyllic, is being lost at unsustainable rates.

See also the 2010 article Britain facing food crisis as world's soil 'vanishes in 60 years' which also quotes Crawford as saying:

It could be as little as 60 years and that is a scary figure because it is not obvious that we have time to reverse decline and still meet future demands for food

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    The key phrase may be 'naturally replenished'. Modern farming often adds nitrogen and other compounds to soil under cultivation. – BobT Jan 23 at 16:22
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    @BobT - or plant soy/beans to naturally replenish nitrogen. But then, why pay attention when facts contradict one's apocalyptic theory – user5341 Jan 23 at 20:58
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    @user5341 That we are not paying enough attention to the kinds of measures you speak of is exactly the basis of the "apocolyptic" theory. The concern stems in no small measure from what our present usage and situation is, and why what could be being done is not. – WetSavannaAnimal Jan 23 at 23:20
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    @DavePhD This is exactly the kind of information I needed. Many thanks. I'll probably make it the "accepted" answer in a few days. – WetSavannaAnimal Jan 23 at 23:22
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    @DavePhD BTW I wouldn't have expected Semedo to be the first. She is the assistant deputy director of the UN FAO, and one would naturally expect her to be citing the common knowledge of her organization rather than being original, which was much of the reason I find it strange that it is rather hard to find good sources for her claim. – WetSavannaAnimal Jan 23 at 23:28

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