Without fertile soil, life on Earth would not be possible | Science and Ecology | DW

Earth is not just dust and dirt, it is home to millions of bacteria that make life possible on this planet. Soils are key to fighting climate change.

In 1937, then-President of the United States, Franklin D. Roosevelt, told his governors in a time of drought and sandstorm: “A nation that destroys its soil destroys itself.”

Perhaps there are those who hear the word “soil” and think of dirt, dirt, or mud. But on World Soil Day, on December 5th, we want to take a look underground to understand why soil is so important to humans and the ecosystem.

Diversity of species ensures human existence

The Earth, the planet on which we grow our grains, fruits and vegetables, on which we form our forests, and where we dig to make our gardens, is the surface through which our planet breathes. It is a mixture of mineral and organic substances, rocky sediments, plants in a state of rot and microorganisms.

Our soil is one of the most diverse living places in the world. A separate world, with worms, insects, bacteria and fungi, pulsing with life. One square meter of land is home to up to 10,000 different species of living things.

About one billion bacteria can be found in just one gram of soil. And 160 people on a football field roughly equals the weight of those bacteria found underground, on the same surface: 11 tons.

These organisms are irreplaceable in the Earth’s life cycle. Fungi and bacteria break down leaves, trees, and organisms. Thanks to this, plants receive the nutrients they need for growth.

Worms, termites and other soil organisms improve soil productivity by mixing the upper layers with their activity. This causes a redistribution of nutrients. In this way, the soil is also aerated and water can be accessed and stored.

We are losing our soil

So far only a fraction of the soil biota has been examined. But what scientists do know is that our soils are diseased and diversity is declining.

According to a United Nations report on soil conditions, most land around the world is in fair, poor or very poor condition. The more life in the soil, the more fertile the land, and this also protects it from erosion, so it will not be easily swept away by wind, rain or flood.

Above all, Brazil, the Caribbean, Central Africa and Southeast Asia have suffered losses due to soil erosion on 70 percent of their arable land.

About half of all fields are planted with monoculture, which is not good for the soil.

A 2015 study showed that over the past 40 years, 33 percent of the world’s arable land has been lost to pollution and erosion. “This is disastrous when you consider that it takes about 500 years for an inch of topsoil to form,” the study authors said.

According to the Food and Agriculture Organization of the World (FAO), about 90 percent of soil could be lost by 2050. An estimated 3.2 billion people already feel poor harvests and its consequences, including rural communities in the Global South. People are from the poorest countries in the world.

Separate farming

The current trend in agriculture still refers to monoculture. Rice, corn, soybeans and wheat alone are grown in more than 50 percent of the world’s cultivated areas.

If large areas are planted with one crop to increase the yield and facilitate the harvest, then eventually this leads to the fact that the soil carries fewer nutrients. This means that farmers rely on synthetic fertilizers that pollute water and alter the natural balance of ecosystems.

But soil is not only a vital factor for the survival of our ecosystem, it is also of central importance in slowing climate change. This is because not all greenhouse gas emissions go into the atmosphere, but are absorbed by plants, forests and the oceans.

Most of Siberia is crossed by carbon dioxide storage in wetlands and peatlands.

When plants die and decompose, much of the carbon dioxide (CO₂) they absorb from the atmosphere is in turn absorbed by the soil. It concentrates twice the amount of carbon dioxide in the plant kingdom and the atmosphere.

In particular, moist and frozen soils store large amounts of carbon dioxide. That is why draining swamps to extract peat doubles the damage to the planet’s climate. Not only are the carbon dioxide deposits destroyed, but by removing water from that soil, the gases that have accumulated there are released, including methane, which is very harmful to the climate.

This also applies to permafrost soils in Antarctica and Canada. As temperatures rise, they melt faster and faster. If they completely disappeared, they would release nearly as much carbon dioxide as if the United States continued to emit the same current amount of fossil fuels annually until the year 2100.

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Swamps all over the world must be re-formed so that they no longer become sources of carbon dioxide.

How can the soil be protected?

If you want to avoid the release of greenhouse gases from dry swamps, you must restore those landscapes on a large scale, says a study in the journal temper nature, published in 2019.

Also, in agriculture, traditional farming methods such as permaculture and subsistence farming can be used, which allow the land to recover. Among these are the alternation of fruit trees in the fields, the combination of plant species in crops, or sowing without machines or a plow. It is not very profitable, but the costs of exploiting the soil in the usual ways are prohibitive.

It is estimated that an increase in soil biodiversity could add up to 2.3 billion tons of additional crops worth $1.4 trillion annually. A sufficient amount of earthworms alone increases crop yield by an average of 25 percent. So healthy soil always pays off.

(cp/lgc)