The Earth’s soil is like the skin on a living being. It’s a protective layer that keeps all other parts together. This protective layer is being stripped away, with half of the Earth’s topsoil lost in the last 150 years (‘Soil Erosion and Degradation’). Understand what is happening, and the kind of impact it has.
What is Soil Erosion?
Soil erosion occurs when a natural or human-driven force, like wind or farming, removes the topsoil from its placement (‘Soil Erosion – Causes and Effects’). The term soil erosion refers to the total loss of topsoil and the nutrients that go with it. Soil erosion is often misused interchangeably with soil degradation, which instead describes the larger, more general process of losing any soil at all (‘Soil Erosion and Degradation’).
The three components to soil erosion are detaching soil from its placement, moving soil to another location, and depositing soil in a new location. Each component has its own impact. Topsoil, which is rich in nutrients and living material, might be moved to another area in the same general location or removed from the location altogether.
Water erosion is the movement of soil by rain, snow, ice, or bodies of water like rivers and oceans. Any moving water that appears muddy or clouded is transporting soil, though many factors play into how much soil is moved (‘Soil Erosion – Causes and Effects’). A very intense rainstorm deposits a tremendous amount of water in a short burst. This type of rainfall is likely to have the greatest and the most noticeable impact on soil movement. Rainfall that is less intense but longer in duration impacts soil movement, especially over time.
Even within water erosion, there are subtypes of erosion. Sheet erosion is the result of raindrop splash or runoff water and occurs evenly over a section of land with a uniform slope. Sheet erosion may go unnoticed until the majority of topsoil has been lost, often redeposited at the bottom of the slope. In rill erosion, surface water becomes concentrated and forms small, well-defined runoff channels. Gully erosion occurs when rill erosion advances, with the channels of runoff water becoming much larger. Bank erosion occurs when channels, whether naturally occurring or man-made, are undercut and scoured (‘Soil Erosion – Causes and Effects’).
Wind erosion is the relocation of topsoil as a result of wind. The term ‘wind erosion’ may call to mind strong winds that lift large quantities of dust or sand into the air, it, like water erosion, can be broken down into various subgroups. Suspension is when particles, typically very fine, are lifted high into the air and carried a great distance. Saltation is when medium particles are picked up by the wind and transported a short distance before dropping back onto the earth. Surface creep describes larger particles being brushed along Earth’s surface.
Tillage erosion is the movement of soil as land is prepared for growing crops. Tillage erosion causes more movement of topsoil than water or wind because it churns up and loosens soil. This makes the soil more vulnerable to forces like gravity, wind, and water (‘Soil Erosion – Causes and Effects’).
Impact of Soil Erosion
The impacts of soil erosion are extensive and far-reaching. All forms of erosion result in decreased quality and quantity of crop yield, textural changes in soil, loss of land, compromised building structures, and hazardous conditions for life.
As topsoil is moved, seedlings and young plants are stripped away. Topsoil takes with it nutrients needed for vegetation to grow, or pesticides needed to protect crops. Similarly, the accumulation of soil and any debris carried with it can damage the area where it’s deposited. This onslaught of soil and debris crushes plants, prevents exposure to sunlight and other nutrients, and unnecessarily spreads pesticides or other chemicals.
Wind erosion can sandblast young plants or bury them as they attempt to take root. Wind erosion contributes to health hazards like allergies and other breathing-related illnesses (‘Soil Erosion – Causes and Effects’).
Soil erosion also leads to increased sedimentation in bodies of water, damaging freshwater habitats and contributing to the decline of fish and other life that depend on the water. Increased sedimentation can clog waterways, changing the flow of water and increases the risk of flooding.
Damage to Soil
As soil is eroded away, so are the nutrients that help support the growth of plants and other microscopic ecosystems. The soil that remains is nutrient-poor, making regrowth more difficult. When topsoil is removed, the lack of organic matter in the subsurface soil makes it more likely to be eroded when exposed to the elements.
What remains underneath the organic topsoil depends upon the location. Usually you will find a clay layer underneath the soil. This is not always the case however. Oftentimes, especially in areas of historically low sedimentation and high runnoff, you will find nothing more than stony bedrock. Neither is very good at growing crops and foodstuffs.
This is why it is important to recognize causes of erosion, so they may be ameliorated. If new topsoil is replaced, there should be a way of mitigating soil erosion for the future.
Different soils have varying levels of resistance to erosion, with texture being the most important factor. Soil comprised of very fine sand, clay, or silt is most vulnerable to erosion. Larger particles of sand, sandy loam, or loam-textured soil are much more resistant to erosion. Aside from the physical characteristics of the soil itself, factors like structure, permeability, and organic matter also play a role in how erodible the soil is. Soils that are permeable, meaning they allow more water to pass through them, resist erosion better, as do soils with more organic matter. Soils that are rough on the surface offer added protection from wind erosion.
To improve resistance to erosion, tackifiers and stabilizers are added to the soil (‘Erosion Prevention Practices – Tackifiers and Soil Stabilizers’). Stabilizers are often organic material, such as straw, mulch, coir, or pine needles, added to the soil as a short-term solution until more permanent organic materials can take root. The primary objective of tackifiers is to bind materials together, making them more difficult for wind and water to move.
Earth’s topsoil is a precious resource that’s being carried away by nature and humans alike. Understanding what soil erosion is and the impact it has are key to making changes that are effective and sustainable.
Erosion Prevention Practices – Tackifiers and Soil Stabilizers. (n.d.). Retrieved February 22, 2019, from https://stormwater.pca.state.mn.us/index.php?title=Erosion_prevention_practices_-_tackifiers_and_soil_stabilizers
FAO.org. (n.d.). Retrieved February 22, 2019, from http://www.fao.org/soils-portal/soil-degradation-restoration/en/
Soil Erosion and Degradation. (n.d.). Retrieved February 22, 2019, from https://www.worldwildlife.org/threats/soil-erosion-and-degradation
Soil Erosion – Causes and Effects. (n.d.). Retrieved February 22, 2019, from http://www.omafra.gov.on.ca/english/engineer/facts/12-053.htm