Sand and Soil

This post contains reviews of a couple of books I've read recently. They relate to a similar theme as the previous post—how people are reshaping the earth.

About the Books

Dirt: The Erosion of Civilizations by Dr. David R. Montgomery is about the history of soil as a requirement for agriculture, and the consequence when it erodes away or its quality deteriorates. The World in a Grain by Vince Beiser is about sand as a commodity—used in everything from concrete to CPUs—and how it is in increasing demand. Both of these books had some interesting things to say. I found The World in a Grain was more readable and engaging, though; Dirt had a tendency to say the same thing over and over in places—for example, a lot of the stats about erosion rates (inches per year or tons per acre per year) would have been better off being summarized and maybe included in a table somewhere for reference.

Dirt starts off with explaining the importance of soil. It then moves on to discussing how soil is in a dynamic balance between its formation (from rocks breaking down and being mixed with organic matter) and rate of erosion, and different types of soils. The main part of the book moves through the history of agriculture, from the initial transition from hunter-gatherer lifestyles to the use of chemical fertilizers and powerful tractors. The places and periods of history it looks at include the ancient near east, classical antiquity in the Mediterranean, medieval Europe, westward expansion in the USA, and isolated Pacific islands. A central idea of Montgomery's books is expressed here:

In the broadest sense, the life span of a civilization is limited by the time needed for agricultural production to occupy the available arable land and then erode through the topsoil. How long it takes to regenerate the soil in a particular climate and geologic setting defines the time required to reestablish an agricultural civilization-providing of course that the soil is allowed to rebuild.

The World in a Grain is divided into two main sections. The first section focuses on uses of sand in the first half of the twentieth century for things like concrete buildings, asphalt roads, and glass. The second section focuses on more recent ways sand is used: silicon computer chips, fracking, beach replenishment, and artificial islands. It also discusses the threat posed by desertification in certain places. The penultimate chapter returns to concrete, which is being used in truly astounding quantities in the twenty-first century as urbanization spreads to almost every country. A recurring metaphor for sand in the book is that the grains are soldiers. In concrete (and asphalt and artificial islands) they have strength in numbers, while for more specialized purposes (e.g. silicon chips or frac sand) "elite" sands are required (but in smaller quantities). This excerpt from the transition between the two main sections summarizes some of the main points of Beiser's book:

In the twentieth century, concrete, asphalt, and glass utterly transformed the built environment for countless millions in the Western world. Armies of sand brought us skyscrapers and suburbs, windows and bottles for everyone, and the paved roads that the automobile depends on. In the twenty-first century, that sand-based way of life is spreading with blinding speed across the entire world. In this new era, the sand armies are taking on even more world-changing missions. Sand is now being used to build entire new lands, to pull oil from previously inaccessible pockets of the earth, and to create the digital devices that permeate our lives. A century and a half ago, sand was a useful accessory, a handy tool for a handful of purposes. Today our civilization depends on it.

With those introductions out of the way, I want to delve into some of the topics that appear in both books, then share some other interesting things I learned from them.

Common Ground

Although sand and soil are not the same thing, there are some processes (e.g. erosion) that affect both of them. I thought this review would be more interesting if I discussed some of the topics that appear in both books together here.

Erosion came up as a concern in both books, especially Dirt. Plowing breaks up soil to make planting easier, but it also leaves it susceptible to being carried away by run-off or wind. The amount lost might seem small, but it adds up over time and over vast areas:

Every second, North America's largest river carries another dump truck's load of topsoil to the Caribbean. Each year, America's farms shed enough soil to fill a pickup truck for every family in the country. This is a phenomenal amount of dirt. But the United States is not the biggest waster of this critical resource.

Fortunately, there are ways to reduce soil erosion that have been understood for a long time (although often not applied due to pressure to maximize yields in the short term or a lack of resources to implement them):

Many soil conservation measures are proven technologies. Measures adopted to curb soil erosion after the Dust Bowl were not new ideas-contour plowing and cover cropping were known more than a century before. Crop rotations, mulching, and the use of cover crops are ancient ideas. So is terracing, which can reduce erosion by 90 percent, enough to offset the typical increase in erosion rates from cultivation.

Apparently there are also methods of "conservation tillage" (and even no-till farming) that are becoming more popular as ways to maintain good soil.

When it comes to sand, Beiser notes that in some places it is collected from riverbeds and beaches. This practice increases erosion. River deltas can shrink when less sediment is reaching them, and the removal of beaches—he notes an incident in Jamaica where an entire quarter-mile-long beach was stolen (from one resort and probably transferred to another)—leaves coasts more vulnerable to erosion.

While I had these books in progress, I was on a business trip to Iowa. On my trip home, while flying between Minneapolis and Chicago, the landscape below (somewhere in western Wisconsin I'd guess) included some of the features I'd been reading about. There are a few spots with what looks like contour plowing or mild terracing and other spots where it looks like gullies are being eroded into the fields.

Aerial view of landscape in western Wisconsin

In The World in a Grain, there is a chapter about mining for frac sand. An excerpt from it relates to soil conservation; topsoil is saved for future mine reclamation:

The topsoil is piled somewhere out of the way; it will be needed to help reclaim the land once the mine is tapped out, as required by law. Mississippi Sand has built a huge berm out of the topsoil, which helps block the neighbors’ view of the mine. Once the sand is all gone, the plan is to restore the hills; they’ll just be about a third smaller than before.

Although it doesn't seem as intensive as some forms of mining, Beiser emphasizes that collecting sand is an extractive industry and is not without impacts. However, protesting against every proposed quarry in your area isn't a good solution either. There has to be a balance. Sand is essential for many things we rely on, and the distance it has to be hauled is a big portion of the cost. And it will come from somewhere:

If you forbid sand mining in your backyard—as many American communities do—then the sand to build your highways and shopping malls will have to be brought in from somewhere else. ... In some situations, well-intentioned efforts to protect the local environment end up simply exporting the damage to somewhere with looser laws and less privileged citizens.

Both books express concern about the most accessible and highest quality deposits of soil and sand, respectively, being used up. Montgomery sees a recurring pattern in history:

In a broad sense, the history of many civilizations follows a common story line. Initially, agriculture in fertile valley bottoms allowed populations to grow to the point where they came to rely on farming sloping land. Geologically rapid erosion of hillslope soils followed when vegetation clearing and sustained tilling exposed bare soil to rainfall and runoff. During subsequent centuries, nutrient depletion or soil loss from increasingly intensive farming stressed local populations as crop yields declined and new land was unavailable. Eventually, soil degradation translated into inadequate agricultural capacity to support a burgeoning population, predisposing whole civilizations to failure. That a similar script appears to apply to small, isolated island societies and extensive, transregional empires suggests a phenomenon of fundamental importance.

This reminded me of something Designed for Dry Feet said about the reclamation of peat bogs in the Netherlands:

Drainage of the peat allowed the inhabitants to create usable agricultural land, but the drawback was subsequent land subsidence. The three major causes of this subsidence were soil shrinkage, consolidation, and oxidation. ...
By the seventeenth century the peat domes had dropped to below NAP. As the reclaimed land subsided, high groundwater levels made the land unusable. Thus, the reclamation process was pushed further up the peat bog as is shown in Figure 1-8. In many cases the new reclaimed parcels simply followed the existing drainage patterns and became extensions of the old parcels. This process was repeated several times and often required the relocation of the entire farm. (p. 10 – 11)

In Indiana, a number of sand dunes along the shore of Lake Michigan were consumed for making glass at factories in Toledo, Ohio. The area was protected by the state government in the 70s and 80s and is now a national park.

Another topic that came up in both books was desertification. Montgomery writes that,

Lowdermilk* blamed overgrazing for unleashing erosion that destroyed the capacity of the land to support people.

*an American who worked on soil conservation around the world; I'll discuss him a bit more below.

Beiser is more poetic:

The vast legions of sand in the world’s deserts are largely useless when it comes to building cities; in some places, as if angry at being left out, they have become threats to those cities.

As he alludes to here, and explains in more detail elsewhere in The World in a Grain, desert sand is not really suitable for construction since its grains are too smooth and therefore don't interlock as well as needed for strong concrete. This leads to the irony of famously-sandy Saudi Arabia importing sand. But it makes me wonder if a way could be found to process/pre-treat desert sand to make it useable. A cost-competitive technique for doing so sounds like it would solve a lot of problems.

In China, a project attempting to stem the spread of the Gobi desert by planting trees is known as the great green wall. But whether the use of a lot of irrigation water to keep the trees alive will cause other problems is still in question. Beiser draws attention to the fact that the same agency is responsible for the project and for evaluating its success:

Considering that the SFA is tasked with both planting millions of trees and assessing whether it’s a good idea to plant millions of trees, you can understand why outsiders are skeptical of their findings.

The fight against desertification there has also involved relocating pastoral communities:

They are some of the hundreds of thousands of mostly Mongol, Kazakh, and Tibetan farmers and herders whom the Chinese government has forced to move off the grasslands and into urban areas, leaving their traditional way of life behind. Officially this is to reduce overgrazing. Many believe it’s also a land grab to free up water and other resources for Han Chinese businesses. In some places the herders have resisted with violent protests.

Using concerns about overgrazing to make traditional herders settle in one place was the subject of a chapter in Water on Sand, a book I reviewed last year.

Other Topics

There were other things I learned from these books (and a few related links I wanted to share) that didn't really fit into the discussion above.

Montgomery seems to worried that the growing global population will exceed the amount of food that can be produced from the amount of land with good soil. He says,

early in the twentieth century it was clear that further population growth would have to come from increasing crop yields rather than plowing more land.

But he also reports that,

Worldwide, over two billion acres of virgin land have been plowed and brought into agricultural use since 1860. Until the last decades of the twentieth century, clearing new land compensated for loss of agricultural land. In the 1980s the total amount of land under cultivation began declining for the first time since farming reached the land between the Tigris and Euphrates. (emphasis added)

This notion of peak farmland was also mentioned in a book I reviewed a few years ago. The author of that book, Ron Bailey, has a more optimistic perspective on it, taking it as a sign that agricultural yields are increasing faster than population. I'm inclined to agree with him. New techniques like vertical farming hold the potential to continue to increase food production without using up more land to do so. Also, Hans Rosling makes a convincing case that population growth is starting to level off (the number of children being born has peaked and further growth will mainly come from the fill-up effect).

This discussion quantifying the potential benefits of soil conservation is a good fit with another book I've read:

Depending on the particular crop and circumstances, a dollar invested in soil conservation can produce as much as three dollars' worth of increased crop yields. In addition, every dollar invested in soil and water conservation can save five to ten times that amount in costs associated with dredging rivers, building levees, and flood control in downstream areas.

Because of my career, I know a bit about the practice of applying wastewater sludge (after digestion/stabilization) to agricultural lands. Dirt has a couple of things to say that support the benefits of adding organic matter and nutrients in this way:

Soil organic matter is essential for sustaining soil fertility not so much as a direct source of nutrients but by supporting soil ecosystems that help promote the release and uptake of nutrients. Organic matter helps retain moisture, improves soil structure, helps liberate nutrients from clays, and is itself a source of plant nutrients.


Eventually it may well be worth reconfiguring the downstream end of modern sewage systems to close the loop on nutrient cycling by returning the waste from livestock and people back to the soil.

Here are some more points from or related to Dirt:

  • In discussing the rise of agriculture, Dr. Montgomery uses Tel Abu Hureyra in Syria as an example. He's very thorough in describing the evidence from this site (and other sites related to some of the other historical periods). Environmental archaeology draws on evidence including things like pollen in lake bed sediment cores, and it's interesting to read about how the clues come together.
  • The book had a good explanation of how soil is in a dynamic balance between erosion and the breakdown of bedrock.
  • Some rivers in China have been built up above their floodplains over the course of centuries. The riverbed gets raised as sediment is deposited and the people raise the dikes higher to match:

Lowdermilk realized that the heavy load of silt eroded from the highlands began to settle out when the river's slope dropped to less than one foot per mile. The more silt built up the riverbed, the faster farmers raised the dikes. There was no winning this game.

  • Loess is a type of soil that is very fertile but also easily eroded.

  • Here is a neat infographic on land use in the USA.

There are also some more things I wanted to share from or prompted by Beiser's book:

  • With my background in civil engineering, I have to show some appreciation for what he had to say about concrete:

On its own, concrete is basically artificial stone. Reinforced with iron or steel, though, it becomes a building material unlike anything found in nature, one that combines the strengths of both metal and stone. That’s what makes it so useful for so many purposes.


Concrete has saved countless lives and enriched even more. Concrete dams generate electricity. Concrete hospitals and schools can be built and repaired far more quickly than their counterparts of adobe, wood, or steel. Concrete roads help farmers get their crops to market, students to get to school, sick people to get to hospitals, and medicines to get to villages in all weathers.

  • But it isn't all rosy, because the sand needed to provide concrete for a rapidly-urbanizing world is sometimes acquired by violence or theft:

At least seventy people were murdered in violence related to illegal sand mining over the same period. The victims include an eighty-one-year-old teacher and a twenty-two-year-old activist who were separately hacked to death, a journalist burned to death, at least three police officers run over by sand trucks and another who had his throat slit and fingers chopped off, all in India. In Kenya, a police officer was slashed to death with machetes, two truck drivers were burned alive, and at least half a dozen other people were killed in fighting over sand.

  • Here is an account of sand being mined in Cambodia to be shipped to Singapore.

  • Thomas Edison wanted to build homes out of concrete. At the time, the idea didn't go anywhere, but now they can even be 3d-printed from concrete.

  • Ralph A. Bagnold was a fascinating individual—a WW2 hero and a sand researcher.

  • As a young officer, Eisenhower participated in a cross-continent vehicle convoy at a time when there were only local roads. The experience clearly stuck with him because when he became president he launched a big strategic project to develop a highway network:

Along with pretty much every other officer on the journey, Eisenhower recommended to his superiors that somebody do something to improve America’s roads. Many years later, he himself got to be that someone. In fact, he would launch the construction of what was for decades the most advanced and encompassing network of paved roads ever built: the US interstate highway system.

  • Building up artificial land is expensive, but it's all relative:

According to the International Association of Dredging Companies, if good quality sand is available within a reasonable distance, new seafront land can be built for less than $536 per square meter—a fraction of the cost of buying existing seafront land in hot spots like Hong Kong, Singapore, or Dubai.


All told, according to a Dutch research group, human beings since 1985 have added 5,237 square miles of artificial land to the world’s coasts—an area about as big as Connecticut or the nation of Jamaica

  • Some of the most dramatic applications (although the Spratly Islands could prove more impactful) have been in Dubai. The world islands are one example, although many of them are still bare patches of sand due to a turndown in the real estate market since the project was started.

  • Beach replenishment is carried out (sometimes at great expense) partly for the tourism value of beaches, but it also has other benefits:

Increasingly, though, beaches are also coming to be valued for something else that might prove even more important than tourist revenue. These seaside armies of sand are a powerful protective force for the people living near them. Beaches are bulwarks that can protect lives and property from storms and rising seas in our climactically imperiled world. Coastal protection has become one of the main justifications for beach renourishment, and with good reason.

Taking this principle further, the Netherlands is deliberate about leaving coastal dunes as a layer of protection from storm surges as I learned from Designed for Dry Feet (referred to above):

The Dutch Dunes are a critical weapon in the defense of the country against the sea. Since much of the land behind the dunes lies below sea level (see Figure 13), any break in the dunes would have catastrophic results. A number of measures have been taken to ensure the stability and continuity of the dunes. As early as the sixteenth century, the government organized efforts to preserve the dunes by planting dune grass or marram. In some locations, backup dikes were constructed behind the dunes. ...
Currents and waves are continually moving sand along the coast. In some areas, there is a net loss, resulting in a recession of the dunes. In other areas, there is a net gain. Today, the primary tool used to combat the recession of the dunes is sand replenishment. In this process, sand is dredged from the North Sea as far as 20 kilometers (12.4 miles) from the coast. ... Sand replenishment locations are determined based on a yearly mapping of the coastline. The objective is to maintain the Dutch coastline at the 1990 reference position (Meijer 1996).
It should be noted that, even at locations that are most at risk, hard measures, such as dams and dikes, are no longer being considered to maintain the coastline. Only soft measures, such as sand replenishment, are applied today. In the long run, hard measures are usually unsatisfactory. (p. 97 – 98)

I'll close this post with some big-picture thoughts about soil and sand from Montgomery and Beiser:

in the big picture, soil regulates the transfer of elements from inside the earth to the surrounding atmosphere. Life needs erosion to keep refreshing the soil-just not so fast as to sweep it away altogether.


Soil truly is the skin of the earth-the frontier between geology and biology.


We humans bind together countless trillions of grains of sand to build towering structures, and we break apart the molecules of individual grains to make tiny computer chips.