Soil degradation is the decline in the quality and productivity of soil, impairing its capacity to support ecosystem services and sustain life. This decline results from improper use or poor management, making the soil less capable of functions like filtering water, cycling nutrients, and supporting plant life. Soil is a finite, non-renewable resource that forms the basis for all terrestrial life.
It can take up to 1,000 years for just a few centimeters of fertile topsoil to form naturally, yet it can be lost or degraded much faster. Healthy soil is a complex, living ecosystem containing millions of cells of bacteria and fungi, which are responsible for nutrient cycling and disease suppression. Protecting this resource is necessary for food production, water filtration, and climate regulation.
How Degradation Occurs
Soil degradation reduces quality across three main categories: physical, chemical, and biological attributes.
Physical Degradation
Physical degradation refers to the deterioration of the soil’s structure, including compaction and crusting. Compaction occurs when soil particles are pressed together, often by heavy machinery, reducing the pore spaces needed for aeration and water infiltration.
Chemical Degradation
Chemical degradation involves changes to the soil’s chemistry that affect nutrient availability. This includes nutrient depletion, where continuous harvesting removes essential elements without replenishment. Other forms are salinization, the buildup of salts from improper irrigation, and acidification, often caused by excessive use of nitrogen fertilizers.
Biological Degradation
Biological degradation is characterized by a decline in the living components of the soil, primarily the loss of soil organic matter and microbial activity. Organic matter feeds the microorganisms and invertebrates that maintain soil structure and cycle nutrients. The loss of organic carbon and biodiversity damages the soil’s ability to support plant growth and regulate its health.
Root Causes of Soil Damage
Degradation is primarily initiated by unsustainable human activities that disturb the soil’s structure and strip its protective cover. Unsustainable agricultural practices are a major driver, particularly intensive tillage, which disrupts soil structure and accelerates the loss of organic matter and topsoil through erosion. Monocropping, the continuous planting of the same crop, also depletes specific nutrients, leading to chemical imbalance.
The removal of natural vegetation through deforestation and land clearing leaves the soil exposed to wind and water, accelerating erosion. Overgrazing by livestock similarly depletes vegetation cover and causes physical compaction of the soil surface.
External factors, such as climate change, worsen degradation by increasing extreme weather events. Prolonged droughts reduce soil moisture, making land susceptible to wind erosion, while intense rainfall increases water runoff and the washing away of topsoil. These pressures are often combined with industrial contamination and improper waste disposal.
Global Impacts of Damaged Soil
Widespread soil degradation poses a direct threat to food security. Declining soil fertility reduces crop yields, and the resulting produce is often less nutritious. Projections suggest that soil erosion could reduce global crop yields by up to 10% by 2050.
The continuous loss of productive land fuels desertification, the expansion of arid lands into formerly fertile areas. Desertification and drought lead to the loss of millions of hectares annually, making agriculture impossible and often forcing populations to migrate.
Degraded soil disrupts the natural water cycle by losing its ability to absorb and retain water. Reduced infiltration capacity increases surface runoff, raising the risk of flooding during heavy rain. Poor water retention also makes the soil vulnerable to drought, reducing the recharge of groundwater reserves.
The loss of biodiversity affects life both above and below the ground. The decline in soil organic matter and the use of chemical inputs destroy the habitats of soil microorganisms and invertebrates. When these organisms are lost, the soil loses its natural ability to perform functions like nutrient cycling and disease suppression.
Reversing Soil Degradation
Reversing soil degradation requires implementing practices that minimize soil disturbance and actively rebuild organic matter.
- Conservation tillage, such as no-till or reduced-till farming, minimizes mechanical soil disturbance between crop seasons. Leaving crop residues on the surface protects the soil from erosion and preserves stable soil structure.
- Cover crops are non-cash crops planted primarily to cover the soil. They protect the soil from erosion, suppress weeds, and add organic matter when incorporated into the field.
- Crop rotation involves alternating different types of crops in a planned sequence. This prevents the depletion of specific nutrients and enhances overall soil structure.
- Agroforestry integrates trees and shrubs into farming systems. Trees serve as windbreaks, reduce erosion, and improve soil structure and water infiltration through their roots.
For immediate erosion control, physical methods like terracing and contour plowing are employed. These techniques involve shaping the land or plowing perpendicular to the slope to slow water runoff and prevent the washing away of topsoil.