What is soil erosion and soil degradation? Although soil erosion is a natural process, human activities over the past decades have greatly accelerated it. In fact, according to the UNESCO, land degradation is undermining the well-being of two-fifths of humanity, driving species extinct and intensifying climate change. According to a senior UN official, all of the world’s topsoil could be gone within 60 years.
Soil Erosion Simple Definition
Soil erosion is a gradual process of movement and transport of the upper layer of soil (topsoil) by different agents – particularly water, wind, and mass movement – causing its deterioration in the long term.
In other words, soil erosion is the removal of the most fertile top layer of soil through water, wind and tillage.
What Is Soil Erosion? A Soil Erosion Scientific Definition
According to a Pereira and Muñoz-Rojas (2017) synthesis, soil erosion is one of the major causes, evidence of, and key variables used to assess and understand land degradation. Soil erosion is a consequence of unsustainable land use and other disturbances, such as fire, mining, or intensive agricultural uses. The loss of soil may have serious impacts on the quantity and quality of soil ecosystem services, with serious economic, social, and political implications.
Different Soil Erosion Causes
Soil erosion is a complex process that depends on soil properties, ground slope, vegetation, and rainfall amount and intensity. According to Montgomery, modifications in land use are one of the most impactful ways of accelerating soil erosion. These changes then have a cascade effect as the loss of fertile topsoil cover sends millions of tons of sediments into lakes and reservoirs, changing ecosystems and impacting agricultural production and water quality. This has been the case with the Bo River in Vietnam.
According to Al-Kaisi from Iowa State University, there are 5 main types of natural soil erosion:
- 1) Sheet erosion by water;
- 2) Wind erosion;
- 3) Rill erosion – happens with heavy rains and usually creates smalls rills over hillsides;
- 4) Gully erosion – when water runoff removes soil along drainage lines
- 5) Ephemeral erosion that occurs in natural depressions.
Despite these types of soil erosion, as we have briefly mentioned above, if it wasn’t for human activities, today’s soils would be less susceptible to erosion and more resilient. What are the human causes behind soil erosion then?
The Main Causes And Impacts Of Soil Erosion
The most effective way of minimizing erosion is to guarantee a permanent surface cover on the soil surface, such as trees, pasture, or meadow. However, compared to original forest soils, soils in pasture fields and croplands have less capacity to hold up and are more susceptible to erosion. These soils also have less capacity to absorb water, which makes flooding (and its economic, social, and environmental impacts) more common.
1. Deforestation for Agriculture Is One of the Top Causes of Soil Erosion
The increasingly high demand of a growing population for commodities such as coffee, soybean, palm oil or wheat is clearing land for agriculture. Unfortunately, clearing autochthonous trees and replacing them with new tree crops that don’t necessarily hold onto the soil increases the risks of soil erosion. With time, as topsoil (the most nutrient-rich part of the soil) is lost, putting agriculture under threat.
2. Soil Erosion is Also Caused by Overgrazing, Which Causes Floods too
Overgrazing is caused by intensive cattle raising. As plants don’t have the recovery period they need, they end up being crushed and compacted by cattle. In this process, topsoil sediments are transported elsewhere. As for the remaining soil, it can lose its infiltration capacity, which means more water getting lost from the ecosystem and a harder time for new plants to grow.
3. Agrochemicals Cause Soil Erosion and Degradation
The use of chemicals under the form of pesticides and fertilizers on (often) monocultural crops is a very usual way of helping farmers improve their yields. However, the excessive use of phosphoric chemicals ends up causing an imbalance of microorganisms in the soil moisture, stimulating the growth of harmful bacteria. As the soil gets degraded, the risk of erosion increases and the sediments sweep (via the actions of water and wind) into rivers and nearby regions, possibly contaminating nearby ecosystems.
At the same time, tillage techniques (that turn over crops and forages) commonly used by farmers to prepare seedbeds by incorporating manure and fertilizers, leveling the soil and taking out invasive seeds also have a large impact. Because it fractures the soil’s structure, tillage ends up accelerating surface runoff and soil erosion.
4. Construction and Recreational Activities
Setting up buildings and roads also have their share of responsibility when it comes to soil erosion as they don’t allow for the normal circulation of water. Instead, it runs off to flood nearby lands, speeded up erosion in these areas. Moreover, motor-based activities such as motocross also have the potential to disturb ecosystems and change (even if at a smaller scale compared with other causes) and erode the soil.
The Importance of Soil, Especially Topsoil
Soil is a very important resource that allows the production of food, fiber, or forages. Despite it being a renewable resource, it renews slowly – generating three centimeters of topsoil takes 1,000 years. Therefore, protecting it is very important to bet on long-term, sustainable agricultural practices since one of the main issues associated with soil erosion is that it comes along a decrease in soil productivity. These productivity losses reduce the quantity and quality of the food we eat.
A study based on the results of 40 soil associations reported that the effects of soil erosion on soil productivity were mostly the result of subsoil properties such as soil water availability, root growth or plow layer fertility – which impact yield results. In the end, with an unfavorable subsoil, erosion is easier and yields and productivity are more greatly affected.
Why Preventing and Stopping Soil Erosion is so Important
According to the UN’s Food and Agriculture Organization (FAO), some key roles of soils are:
- Soils help fight and adapt to climate change by collecting and storing carbon and reducing greenhouse gas emissions (GHG) in the atmosphere;
- Resilient soils allow for water infiltration through the soil, filtering pollutants and preventing them from leaching into the groundwater;
- Soils capture and store water for crops, whereas degraded soils retain less water;
- Reducing surface evaporation and increasing water use efficiency and productivity are also processes enhanced by healthy soils;
- Soils provide fiber, fuel, medicinal products, and other ecosystem services;
- Soils are home to 1/4 of biodiversity and they are a key part of the global cycles that make all life possible.
Arable, Fertile Land Is Being Lost at An Incredible Speed
- Experts from the Grantham Centre revealed at COP21 in Paris (2015) that erosion rates from plowed fields average 10-100 times greater than rates of soil formation and nearly 33% of the planet’s arable land has been lost to erosion or pollution in the last 40 years.
- If we are aware of the fact it takes about 500 years to form 2.5 cm of topsoil under normal agricultural conditions, today’s agriculture is clearly unsustainable in the long-term and is slowly destroying the world’s ecosystems and the biodiversity they are home to. Among other problems is the wide use of ammonia fertilizers, massified by the Haber-Bosch method, with the primary goal of helping increase crop yields but with devastating consequences in marine ecosystems.
- The academics from the Grantham Centre proposed a couple of solutions to fight soil loss and degradation. Among them are: 1) using biotechnology to wean plants off their dependence upon fertilizers; 2) including recycling nutrients from sewerage or 3) rotating crops with livestock areas to relieve pressure on arable land. There are, nonetheless, other ways of protecting the soil.
How to Prevent Soil Erosion
Despite the fact human activities have accelerated soil erosion, there are ways of repairing the damage we have created. From reforestation and windbreaks to stone walls or more sustainable agriculture techniques. Let’s analyze them in greater detail.
1. Stopping Soil Erosion via Sustainable Farming Practices
Regenerative agriculture techniques have the potential to preserve and restore ecosystems and habitats and improve the quality and health of the soil.
2. Protecting the Soil by Planting Windbreaks
Windbreaks are linear plantings of shrubs and trees with the goal of improving crop production, protect the soil, people, and livestock. According to FAO, windbreaks can reduce wind velocities for a distance approximately 15 times the height of the tallest trees. As a result, there is a lower rate of soil loss across large crop areas.
3. Stone Walls to Prevent Soil Erosion
According to Camera et. al (2018) the sediments accumulating behind the dry-stone walls create suitable land for farming and prevent soil erosion.
4. Reforestation Helps Protect Soils
According to FAO, reforestation helps reduce sedimentation rates in downstream valleys. According to this UN agency, reforestation on unstable land and around water regions such as rivers increases the water-retention capacity of land and improve water quality, both of which benefit food production. Moreover, according to a recent study published in Nature, reforestation also has a tremendous potential to help fight climate change as trees capture huge amounts of CO2.
5. Conservation Tillage and Soil Erosion
Conservation tillage stands for as any form of tillage that minimizes the number of tillage passes. Conservation tillage techniques have the potential to reduce the vertical movements of soil. In this way, more crop residues are left on the soil surface reducing the exposure to water or wind erosion.
Quotes on Soil Erosion
Every 5 seconds, the equivalent of one soccer field is lost due to soil erosion.
FAO, bringing attention to the fact that although soils are essential for human well-being and the sustainability of life on the planet, they are threatened on all continents by natural erosion.
The dirt beneath our feet is getting poorer and on many farms worldwide, there is less and less of it.
Extracted from an article within the series Follow the Food by BBC Future
A nation that destroys its soil destroys itself.
Quote by Franklin D. Roosevelt in a letter to all State Governors on a Uniform Soil Conservation Law.
Soil is lost rapidly but replaced over millennia and this represents one of the greatest global threats for agriculture.
Duncan Cameron, Professor of Plant and Soil Biology at the University of Sheffield