/Topsoil Degradation, Soil Erosion, and Soil Governance (Global or Otherwise)

Topsoil Degradation, Soil Erosion, and Soil Governance (Global or Otherwise)

By Lambert Strether of Corrente

I wish I could be doing a cheerful perambulation through soil taxonomies (again), but today I want to focus, at a high level, on two escalating problems with soil: The degradation of our (the world’s) topsoil, important because that’s where grow our food, at least so far; and the loss of soil as such, due to erosion (we just looked at the effects of erosion on river systems in considering sediment). The press seems to have addressed topsoil first, a couple of years ago, and then, this year, science has gone on to erosion. I will then avoid a deep dive, or indeed any kind of dive at all, into technical solutions for soil issues (for example, no-till, regenerative agriculture, sustainable practices, soil health, or recarbonization), and look at briefly at “governance” issues instead. Paradoxically, soil is both a private asset and a public good; institutionally, we do not seem to have been able to address or even approach this contradiction.[1]

Topsoil Degradation (and the “60 Harvests” Figure)

What is topsoil? In a previous post, we presented this definition:

A: This upper soil horizon is also called Topsoil. It is only between 5 to 10 inches thick and consists of organic matter and minerals. This is the soil layer where plants and organisms primarily live.

And this chart (here modified):

Unfortunately, topsoil is degrading. From the Guardian, “The world needs topsoil to grow 95% of its food – but it’s rapidly disappearing“, May 2019:

The world grows 95% of its food in the uppermost layer of soil, making topsoil one of the most important components of our food system. But thanks to conventional farming practices, nearly half of the most productive soil has disappeared in the world in the last 150 years, threatening crop yields and contributing to nutrient pollution, dead zones and erosion. In the US alone, soil on cropland is eroding 10 times faster than it can be replenished.

If we continue to degrade the soil at the rate we are now, the world could run out of topsoil in about 60 years according to Maria-Helena Semedo of the UN’s Food and Agriculture Organization.Without topsoil, the earth’s ability to filter water, absorb carbon, and feed people plunges. Not only that, but the food we do grow will probably be lower in vital nutrients.

The modern combination of intensive tilling, lack of cover crops, synthetic fertilizers and pesticide use has left farmland stripped of the nutrients, minerals and microbes that support healthy plant life[2].

60 years (at least in the United States) would 60 harvests. That’s not very many. For many of us, the endpoint would come not in our grandchildrens’ lives, but in our childrens’. It would also be a really good idea to have stopped degrading the soil some time ago. Scientific American:

Generating three centimeters [1.18 inches] of top soil takes 1,000 years.

Having rung the alarm bell, let me now at least muffle it. From the New Scientist, “The idea that there are only 100 harvests left is just a fantasy,” from 2019:

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.

… 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…. [B]ut 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.

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…. 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.

(One might speculate that the UN’s exaggeration and headline-seeking was driven by institutional weakness.) I will have more to say under “Soils and Governance” about agricultural endpoints (which I, unlike Wong, believe are real, regardless of the spurious precision of “60 years.”)

Soil Erosion

Now let’s look at soil erosion, where we have a major new study in PNAS, “Land use and climate change impacts on global soil erosion by water (2015-2070),” published on September 8. First, an overview on erosion (footnotes omitted):

Contemporary societies live on a cultivated planet where agriculture covers ∼38% of the land surface. Humans strongly depend on the capacity of soils to sustain agricultural production and livestock, which contributes more than 95% of global food production. The underlying agricultural systems are at the same time major drivers of soil and environmental degradation and a substantial source of major biogenic greenhouse gas emissions. The latest United Nations (UN) report on the status of global soil resources highlights that ‘…the majority of the world’s soil resources are in only fair, poor, or very poor condition’ and stresses that soil erosion is still a major environmental and agricultural threat worldwide. Ploughing, unsuitable agricultural practices, combined with deforestation and overgrazing, are the main causes of human-induced soil erosion. This triggers a series of cascading effects within the ecosystem such as nutrient loss, reduced carbon storage, declining biodiversity, and soil and ecosystem stability.

And now methodological issues (reinforcing Wang’s remark above on “how incredibly complex the calculations needed to make such predictions would be”):

Modeling soil erosion at global scales is challenging, physical models are too data intensive and the data are sparse, therefore adopting a semiempirical approach represents the state of knowledge and a pragmatic approach to informing policy. Only two studies have been successful at attempting future global soil erosion estimates, both at coarse scale (∼50 km or greater), using old climate projections and hence, impractical for policy making intervention…. Since [Yang and Ito’s] efforts, substantial progress has been made, both in terms of land use and climate projection. Recent advancements in remote sensing, wider availability of earth observation data, and increased processing of big datasets have enabled the development of new global vegetation indices and land cover products with both higher spatial resolution and accuracy… The same goes for the recent release of climate datasets, including bias-corrected climate projections of multiple bioclimatic variables, which through robust spatial interpolation methods allow computation of global estimates of rainfall erosivity, more closely related to rainfall intensity than rainfall volume.

And the results, from the abstract. Three scenarios are considered:

Here we predict future rates of erosion by modeling change in potential global soil erosion by water using three alternative (2.6, 4.5, and 8.5) Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios. … Our future scenarios suggest that socioeconomic developments impacting land use will either decrease (SSP1-RCP2.6–10%) or increase (SSP2-RCP4.5 +2%, SSP5-RCP8.5 +10%) water erosion by 2070. Climate projections, for all global dynamics scenarios, indicate a trend, moving toward a more vigorous hydrological cycle, which could increase global water erosion (+30 to +66%).

Here is a map that includes the most recent data (2015) and all three scenarios:

You will notice that the American Midwest is hit in scenarios B and C (important when we discuss Iowa below). Summing up:

The multiscenario comparison suggests that although future land use changes can notably affect global soil erosion processes through the expansion or contraction of croplands, a global climate potentially moving toward more vigorous hydrological cycles would be acting as a major driver of future increases in soil erosion.

Soil and Governance

Sol is simultaneously a public and private good. From Dr. Anna Krzywoszynska of the Soil Alliance, in “Soil: Private Asset or Public Good?“:

On the one hand, farmers sometimes describe soil as their ‘factory floor’, their ‘key asset’, and their private concern. On the other, soil is a vital factor in the bio-geo-chemical cycles which maintain life on the planet, and through these to the provision of for example drinking water and breathable air, making it a public good, and so a public concern.

And from the Sustainable Soils Alliance, “The Economics of Soil: Private Asset or Public Good?

80% of the costs associated with degraded soils occur off-site and so are either invisible or of limited concern to those whose actions may be causing them. Professor Morris described a fundamental ‘disconnect’ between the way soils are used and the broader consequences for society and the economy.

On a similar note, Guy Thompson of En Trade explained that land managers don’t know the value of the environmental services they have to offer from their land and government doesn’t understand land’s potential. The lack of mechanisms to measure and demonstrate this and so align incentives accordingly represents a market failure and failure of soil governance, and therefore justification for government intervention.

Very well. So, if soil is a public concern, and government intervention is justified to protect it, in what forum are such concerns to be addressed, and what form does intervention take? We might look to international agencies, like the United Nations Food and Agriculture Organization (FAO). From their page on “Soil Governance“:

Policies and strategies

Soil governance concerns policies and strategies and the processes of decision-making by nation states and local governments on how the soil is utilized.

What is the governance of soils about?

Governing the soil requires international and national collaboration between governments, local authorities, industries and citizens to ensure implementation of coherent policies that encourage practices and methodologies that regulate the usage of the soil resource to avoid degradation and conflict between users.

Needless to say, this “governance” isn’t worthy of the name[3] (though FAO does a lot of worthy technical work, as for example on locusts). Soil is not addressed as a public good common to all stakeholders (hardly to be expected, since the UN has no monopoly on violence, unlike States). So we turn to the national level, using the state of Iowa, in the United States, as a miniature case study. First, we’ll look at Iowa’s soil, and establish that there is indeed an “endpoint” (contra Wang). Then, we’ll look at the governance structures that control and impact Iowa’s soil.

Iowa “produces one-eleventh of the nations’ food supply and is the largest producer of corn, pork and eggs, and second in soybeans in the United States.” Iowa’s soil is prairie soil. It is classified — yes, there is a classification system from the USDAas a “mollisol”:

Mollisols (from Latin mollis, “soft”) are the soils of grassland ecosystems. They are characterized by a thick, dark surface horizon [Layer A in the diagram of topsoil above]. This fertile surface horizon, known as a mollic epipedon, results from the long-term addition of organic materials derived from plant roots. Mollisols are among some of the most important and productive agricultural soils in the world and are extensively used for this purpose….

Mollisols primarily occur in the middle latitudes and are extensive in prairie regions such as the Great Plains of the U.S. Globally, they occupy approximately 7.0 percent of the ice-free land area. In the U.S., they are the most extensive soil order, accounting for approximately 21.5 percent of the land area.

You will recall that topsoil is typically between 5 to 10 inches deep. Mollisol is (or was) between 23 and 31 inches (60 to 80 cms). However, Iowa’s mollisol is getting thinner and thinner. From Iowa PBS :

When Iowa land was first plowed, the settlers found 14 to 16 inches of topsoil. By 2000 the average was six to eight inches. When the prairie plants were plowed under, the soil was to exposed and vulnerable to erosion. Soil erosion is the process of removing soil materials from their original sites by water or wind. Hard rains that wash across bare soil move Iowa’s black gold into gullies and streams. During dry weather winds can carry loose soil across the countryside. If nothing is done to stop the erosion, the rest of Iowa’s topsoil could be gone in the next 100 to 150 years.

So there’s your endpoint: 8 inches per century means 0 by 2100 (and faster if the degradation is worse). No more mollisol[4].

So what is the governance structure for soil in Iowa? We do have plenty of individual (i.e., private) effort. From Civil Eats:

Guthrie had help from the Iowa State University (ISU) STRIPS (Science-based Trials of Row-crops Integrated with Prairie Strips) program, which was founded in 2003 by scientists hoping study the effects of strategically planted native prairie for soil, water, and biodiversity benefits on farms. After 10 years, the team began to publish a series of papers laying out their results. They found that adding a prairie to a small fraction of a farm yields impressive benefits for water quality and nutrient retention, reducing erosion, providing habitat, and other benefits. In the years since, the ISU team has been working to help more farmers create native prairies.[5]

We have technical assistance, again adopted on an individual (i.e., private) basis:

As farmers and natural resource managers use the Daily Erosion Project to visualize erosion across space and time, the urgency of soil conservation is brought to focus.

And of course, we have good individuals trying to do the right thing (again, privately):

But over the past 17 years, Wolf’s relationship with the land has changed. No longer is the Miles farm simply a land investment.

Now, she sees the land as a part of nature, and makes decisions about her farm accordingly. Wolf introduced buffer strips to control soil runoff; developed a wetland to collect rain runoff and invite migratory birds; prioritized pasture maintenance; and began to restore a stream bank.

Her farm, in Jackson County three miles from the Mississippi River, is vulnerable to topsoil erosion. All of the measures she’s taken were with an understanding of the hilly landscape’s fragility and an acceptance that, without soil, food cannot be produced.

But Wolf’s practices are in many ways an exception to the rule when it comes to Iowa farms.

However, here’s how soil governance in Iowa really works. From Iowa PBS:

Twenty-three million acres — some 75 percent of Iowa’s farmland — is used to grow corn and soybeans, most all of it through what’s known as industrial agriculture, using expensive equipment and a massive amount of chemical fertilizers and pesticides. Those two crops are highly subsidized by the federal government, to the tune of hundreds of millions of dollars a year. And corn and soy are mostly grown to produce ethanol and animal feed. The remainder that’s eaten by humans is mostly in the form of junk food.

Hard to see much concern for the public good here. I selected Iowa as a case study not only because it’s losing its topsoil, and in at least two scenarios will be subject to global water erosion, but because it enjoys disproportionate political influence as our first-in-the-nation primary (or caucus) election. Quoting from Iowa Starting Line, which covers such matters, in “Iowa’s ‘Black Gold’ Is Washing Away“:

Republicans love to brag that they are the true conservatives. How can these self-proclaimed conservatives refuse to acknowledge the disappearance of Iowa’s greatest natural resource? Safeguarding Iowa’s soil should be priority number one for anyone that claims to be a conservative.

Iowa Democrats have advanced a number of proposals to address Iowa’s soil loss and water pollution. In 2016, Senator Joe Bolkcom offered a check-off solution to provide the needed funds.

“Let’s use the voluntary check-off approach that corn and soybean growers, pork, cattle, poultry and egg producers already use to generate tens of millions annually to support their marketing and research plans,” said Bolkcom. In addition, Iowa Democrats have pushed for other funding proposals for conservation measures. They have repeatedly called for funding the voter approved Natural Resources Trust Fund. Republicans refuse to listen to the 63% of Iowans that voted to approve that conservation measure.

As you can see, treating soil as a public good as well as a private asset — let alone instead of a private asset — just isn’t on the radar for either party. At all. In 2016 — and, so far as I know, 2020 — the issue hasn’t even come up (not even “green payments,” which again preserve paradigm that land, hence soil, is a private asset only). The irony here is that Iowa’s civic institutions do not seem to me to be particularly weak. Yet as the soil that is the basis of their prosperity erodes beneath their feet, they cannot see soil as the public good it is. I wish I could come to a happier conclusion, but we are where we are. Il faut cultiver notre jardin..


Nature has recently published “A recipe to reverse the loss of nature“, another modeling exercise. It’s not about soil per se, but about biodiversity:

By nature, we mean the diversity of life that has evolved over billions of years to exist in dynamic balance with Earth’s biophysical environment and the ecosystems present. Nature contributes to human well-being in many ways, and the services [“Nature As A Service”?] it provides, such as carbon sequestration by plants or pollination by insects, could impose a vast cost if lost.

Here too the issue is not “the science,” but governance:

Although the models say that a better future is possible, is the combination of the multiple ambitious conservation and food-system interventions considered by Leclère et al. a realistic possibility? Achieving each one of the conservation and food-system actions would require a monumental coordinated effort from all nations. And even if the global community were to get its act together in prioritizing conservation and food-system transformation, would such efforts come in time and be enough to save our planet’s natural legacy? We certainly hope so.

What would “the global community” getting “its act together” look like, operationally? I don’t think anyone knows.


[1] For all I know, some anthropologist or field economist has given the lie to this claim, something I would very much like to have happened. Readers?

[2] When I still thought this was going to be a cheerful perambulation post, I collected a lot of great links on the wondrous complexity of soil. In no particular order: Microbial diversity, microfauna, “uninhabited surface soil environments” in Antarctica, “the contentious nature of soil organic matter,” hidden webs of fungi, and so forth. The extraordinary and wild systemic profusion, for me — speaking intuitively and tendentiously — seems to call into question the very notion of “ecoystem services” which seems more appropriate for generating dollar figures for grant proposals than anything else (“We find that, so far, the economic valuation of soil-based ecosystem services has covered only a small number of such services and most studies have employed cost-based methods rather than state-of-the-art preference-based valuation methods, even though the latter would better acknowledge the public good character of soil related services. Therefore, the relevance of existing valuation studies for political processes is low.”) magine “body services” as a concept in medicine, for example [shudder].

[3] Here is U-North Bayer using its participation in the FAO’s “Global Soil Partnership” as a public relations scheme.

[4] Hilariously, one suggestion is to “save the phenomena” of mollisol by changing the criteria for classifying it so that Iowa retains the name, mollisol, if no longer the substance: “[U]nder the principle of following the genetic thread to classify soils, the taxonomic system should be modified to accommodate the eroded units that have the same genetic pathway as their uneroded counterparts. This could be accomplished by placing primary emphasis on the organic carbon content and waiving the color requirement [“black”] for eroded soil map.”

[5] From the same source: “When farmer Gary Guthrie describes recent changes to his farm, his eyes light up. After adding native prairie to his central Iowa operation, he remembers hearing the hum of pollinators flocking to the property. ‘Oh, my goodness, it was stunning, the level of buzzing,’ Guthrie said. ‘That moment was sort of an awakening for me.’ The presence of so many bees and other insects was an indicator, to Guthrie, of the health of the land.” I honestly think that the presence of beauty is a really good sign that matters. After all, if sensing beauty were not adaptive, we wouldn’t have developed the ability to do it, would we? (Perhaps — now speculating freely — just as plants, as Michael Pollan shows in The Botany of Desire, evolve to both appeal to and shape human desire, why would not the natural landscape?

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