Soil Degradation and Restoration

Soil degradation is the decline in the quality and capacity of soil through physical, chemical, and biological deterioration, and restoration is the set of practices that reverse that decline and rebuild soil function.

Definition

Soil degradation is the deterioration of soil quality through loss of structure, organic matter, nutrients, or biological function and through erosion, salinization, compaction, or contamination; soil restoration is the deliberate reversal of these processes to recover soil quality and function.

Scope

This topic covers the major forms of soil degradation, including erosion, organic matter loss, compaction, salinization, acidification, and contamination, the processes that drive them, and the principles and practices used to restore degraded soils. It frames conservation as not only preventing damage but also recovering soils that have already deteriorated.

Core questions

• What are the major forms and drivers of soil degradation?
• How do erosion, organic matter loss, and compaction degrade soil function?
• How can degraded soils be restored?
• How does restoring soil quality relate to carbon storage and food security?

Key concepts

• Soil quality and soil health
• Erosion and topsoil loss
• Organic matter and nutrient depletion
• Compaction and structural degradation
• Salinization, acidification, and contamination
• Soil restoration and rehabilitation

Key theories

Soil quality decline through degradation processes

Erosion, depletion of soil organic matter and nutrients, compaction, acidification, salinization, and contamination each reduce the soil's capacity to function, often interacting so that degradation in one property accelerates loss in others.

Restoration through rebuilding organic matter and structure

Restoring degraded soils centres on rebuilding soil organic matter and structure and re-establishing biological activity through residue and cover management, reduced disturbance, and amendment, which simultaneously improves fertility and can sequester carbon.

Mechanisms

Degradation typically begins with loss of protective cover and soil organic matter, which weakens aggregate structure and makes the soil more erodible, less able to hold water and nutrients, and more prone to compaction; salinization, acidification, and contamination add chemical deterioration. Restoration reverses this sequence by returning organic inputs, reducing disturbance, controlling erosion, and where needed amending chemistry, so that structure, biological activity, and nutrient and water retention rebuild over time, often slowly.

Clinical relevance

Soil degradation threatens the productivity of a large share of the world's agricultural land and the ecosystem services soils provide, while restoration can recover yields, improve water quality, and store carbon; managing degradation and restoration is therefore central to food security, environmental quality, and climate-change mitigation.

History

Concern with soil degradation grew through the 20th century from the visible disasters of erosion toward a broader recognition of chemical, physical, and biological deterioration. Late-20th- and early-21st-century work, much of it by Rattan Lal, framed restoring soil quality as a strategy linking land productivity, food security, and carbon sequestration.

Key figures

• Rattan Lal
• Nyle C. Brady
• Ray R. Weil

Seminal works

• lal2015
• lal2004
• brady2016

Frequently asked questions

What are the main types of soil degradation?

The major types are physical degradation such as erosion and compaction, chemical degradation such as nutrient depletion, acidification, salinization, and contamination, and biological degradation such as loss of organic matter and soil life; these often occur together and reinforce one another.

Can degraded soils recover?

Many degraded soils can be restored by rebuilding organic matter, controlling erosion, relieving compaction, and correcting chemical problems, though recovery is often slow and incomplete; severely eroded or contaminated soils may take a very long time or require intensive intervention.