Topsoil Is Disappearing
There’s only a thin layer of soil that sustains us by providing the growing medium for 95 percent of our food. However, intensive farming practices and other assaults have caused enormous damage to the world’s topsoil. As the World Wildlife Fund puts it, “Half of the topsoil on the planet has been lost in the last 150 years.”
The Biology of Soil
It might look like just a bunch of dirt, but topsoil is a very complex mixture of organisms. An often-quoted anecdote is that there are more organisms in a handful of soil than there are people on Earth. The Soil Science Society of America adds that “Soils are the stomach of the earth, consuming, digesting, and cycling nutrients and organisms.”
Soil is, or should be, teeming with bacteria, algae, nematodes, insects, and millions of other organisms. They all interact with each other to produce the chemical and physical structure that sustains plants.
Soils are a fundamental natural resource, and are the basis for all terrestrial life. Avoiding soil degradation is crucial to our well-being.— New South Wales Office of Environment and Heritage
It takes about 1,000 years to create three centimetres of topsoil, but we are degrading it far faster than it is being formed. According to the United Nations, 24 billion tonnes of healthy topsoil are being lost each year.
In 2017, Maria-Helena Semedo of the Food and Agriculture Organization issued the startling warning that “if current rates of degradation continue all of the world’s topsoil could be gone within 60 years.”
Modern Farming Methods
For centuries, farmers rotated crops and often left pastures fallow for a while to give them a chance to rest and recuperate. Of course, as the world’s population has increased, the demand for food has also risen, triggering the use of more intensive agricultural techniques.
The monoculture of a single crop such as corn or soybeans planted on the same ground year after year has become more popular. To increase yields, chemical fertilizers, herbicides, and pesticides are applied. These artificial inputs have the side effect of killing many of the beneficial microbes that maintain soil chemistry.
Applying agrochemicals to the land boosts crop yields—for a while. However, it’s not sustainable over the long haul. According to the United Nations, this has led to the degradation of a third of the world’s cropland.
Back in the day, when old Ned plodded across the fields pulling a plough, he did little damage to the soil; he even enhanced it once in a while with a contribution of manure. Today, massive tractors weighing 25,000 pounds thunder across the landscape, compacting the soil under their massive wheels.
And here’s what Green Facts says about that: “Soil compaction induced by machinery use leads to a reduction in biological activity, porosity, and permeability. It reduces water storage and conduct and makes soil less permeable to plant roots, it can affect water infiltration capacity and increase erosion risk by accelerating run‐off.”
But there’s more to blame than farming.
Cutting down the world’s forests has a big negative impact on soil.
Here’s American Forests: “More than 99 percent of old-growth, eastern forests have been cleared for agricultural and urban environments or have been replaced by second-growth forests devoid of the once-dominant American chestnuts. The oak savannas of the Midwest have been reduced to tiny remnants crowded by corn fields. Diverse, ancient forests of the Pacific Northwest have been clear-cut and replaced with a monoculture of skinny, young trees in a checkerboard pattern right up to national park boundaries.”
Clearing all that forest cover has a major impact on soil, which contains three times more carbon than the atmosphere. The British Broadcasting Corporation points out that the soil is then “eroded, compacted by machinery, built over, or harmed by over-watering.
“Hurting the soil affects the climate in two ways: it compromises the growth of plants taking in carbon from the atmosphere, and it releases soil carbon previously stored by worms taking leaf matter underground.”
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services says that degraded soil has a negative effect on about 3.2 billion people worldwide.
The group’s Chairman, Professor Sir Bob Watson, warns, “That’s almost half of the world population. There’s no question we are degrading soils all over the world. We are losing from the soil the organic carbon and this undermines agricultural productivity and contributes to climate change. We absolutely have to restore the degraded soil we’ve got.”
The damage has already been done in North America. The current hotspots for soil degradation caused by deforestation are South America, sub-Saharan Africa, India, and China.
As the world’s population numbers have exploded, so have the size of the cities in which people live. New suburbs march outwards from city centres and gobble up prime agricultural land.
As a new concrete foundation is poured another section of good quality soil is covered up forever. A 2014 Canadian government report noted that during the previous decade almost one million hectares (more than 3,800 square miles) of “dependable agricultural land” vanished under houses, factories, warehouses, and roads.
This rapid consumption of valuable land is replicated all over the world as mega-cities grow ever more mega. And, the process has been going on for centuries.
A team from the University of Maryland tells us that 300 years ago, humans were using about five percent of the available land. Today, more than half the land is under the plough or under human habitation.
- The United Nations has declared that December 5 is World Soil Day.
- Up to one billion bacteria are contained in a single gram of fertile soil.
- An acre of healthy soil will contain between 100 and 1,000 pounds of earthworms.
- “Soil Erosion and Degradation.” World Wildlife Fund, undated.
- “Soil Biology.” Soil Science Society of America, undated.
- “Only 60 Years of Farming Left If Soil Degradation Continues.” Food and Agriculture Organization, December 5, 2017.
- “The World Needs Topsoil to Grow 95% of its Food – but it’s Rapidly Disappearing.” Susan Cosier, The Guardian, May 30, 2019.
- “Third of Earth’s Soil Is Acutely Degraded Due to Agriculture.” Jonathan Watts, The Guardian, September 12, 2017.
- “Erosion, Biodiversity, Contamination and the Declining State of Soil in Europe.” Greenfacts.org, undated.
- “Anthropogenic Transformation of the Biomes, 1700 to 2000.” Erle C. Ellis, et al, Global Ecology and Biogeography, 2010.
© 2019 Rupert Taylor