IB ESS: Main Causes of Soil Degradation (2026)

Soil looks calm. Quiet. Almost bored.

But in IB ESS, soil is a living system with inputs, storages, transfers, and outputs. And when that system gets pushed past its limits, it doesn’t usually fail with drama. It fails slowly: a thinner topsoil layer after every storm, a little more salt after every irrigation cycle, a little less organic matter after every harvest.

That slow decline is exactly why soil degradation matters in IB ESS (2026 first assessment). It connects the syllabus threads students are always asked to link: food production systems, land use change, sustainability, ecosystem services, and human wellbeing.

Quick checklist: what you must be able to do for IB ESS

Before you memorise any case studies, make sure you can do these five things quickly (Paper 1 speed, Paper 2 clarity):

• Define soil degradation as a loss of soil quality and function.

• Name the main causes of soil degradation and explain the mechanism.

• Link each cause to at least one consequence (environmental, social, economic).

• Use at least one named case study with each cause (even briefly).

• Suggest realistic management strategies (and evaluate trade-offs).

For the core soil content, start with the RevisionDojo hub for Soil systems and terrestrial food production and build from there.

What is soil degradation in IB ESS?

In IB ESS, soil degradation means the decline in soil’s ability to function as a system: supporting plant growth, cycling nutrients, storing carbon, filtering water, and providing habitat for organisms.

A useful exam phrasing is: soil degradation reduces fertility, structure, and biodiversity in soil, often lowering agricultural productivity and weakening ecosystem resilience.

If you need a quick refresh on how soil works as a system (horizons, inputs/outputs, transfers), use Notes for 5.1 Soil.

The main causes of soil degradation in IB ESS

Erosion (water and wind)

Erosion is the removal of topsoil by water or wind. In natural conditions it happens slowly, but human land use can accelerate it sharply.

Common accelerators you should mention in IB ESS answers:

• Deforestation (less interception, fewer roots binding soil)

• Overgrazing (vegetation cover removed, soil exposed)

• Poor cultivation on slopes (runoff increases)

Key impacts:

• Loss of fertile A-horizon (lower yields)

• Sedimentation of rivers (water quality and aquatic habitats)

• Higher risk of desertification in drylands

Classic case study: the Dust Bowl (USA, 1930s) where drought plus unsustainable ploughing increased wind erosion.

To practise writing causetoconsequence chains, use the 5.3 Soil degradation and conservation Questionbank.

Salinization

Salinization happens when salts build up in soil, commonly in arid and semi-arid areas where irrigation water evaporates and leaves dissolved salts behind. Poor drainage makes it worse.

Why examiners like it: it’s a clean example of a human action (irrigation) creating an unintended feedback that reduces productivity.

Key impacts:

• Osmotic stress for plants (harder to absorb water)

• Reduced crop growth and potential long-term infertility

Named example often used: the Indus Valley region (Pakistan), where large-scale irrigation has contributed to widespread salinity issues.

Nutrient depletion and loss of soil organic matter

Nutrient depletion occurs when crops remove nutrients faster than they are replaced. This is especially common with continuous monoculture, limited fallow time, and low organic inputs.

In IB ESS, link nutrient loss to:

• Reduced soil fertility and yields

• Greater reliance on fertilisers (economic costs, pollution risks)

• Declining soil structure (less humus means weaker aggregates)

A common regional example is parts of Sub-Saharan Africa where nutrient-poor soils combined with intensive cultivation can exhaust fertility.

To connect soil fertility to why soils matter in ecosystems, revise Contribution of soil notes.

Desertification

Desertification is land degradation in drylands driven by climate variability and human activity. In IB ESS, it’s not “deserts expanding by nature alone”, it’sit’s often about pressure on fragile soil systems.

Human drivers students should be ready to evaluate:

• Overgrazing and fuelwood collection

• Unsustainable cultivation of marginal lands

• Poor water management

Key impacts:

• Falling agricultural productivity

• Increased food insecurity and migration pressures

Named case study: the Sahel (Africa), where variable rainfall plus land use pressure has contributed to desertification risks.

Pollution (toxins and excess chemicals)

Soil pollution can involve pesticides, hydrocarbons, industrial waste, or heavy metals. It reduces soil biodiversity, harms food chains, and can contaminate groundwater.

For IB ESS, focus on:

• Why soil is a sink for pollutants

• How pollutants move (leaching, runoff, bioaccumulation)

• Trade-offs between agricultural productivity and environmental health

A named example sometimes used in environmental courses is Minamata (Japan) for mercury contamination impacts across ecosystems (including surrounding land).

Compaction

Compaction happens when heavy machinery or trampling compresses soil, reducing pore spaces.

Why it matters:

• Less infiltration (more surface runoff)

• Less oxygen in soil (reduced root growth and soil organism activity)

• Greater erosion risk due to increased overland flow

It’s a straightforward mechanism question that can score well if you explain porosity clearly.

Human vs natural causes (what examiners want you to say)

You can mention droughts, storms, and floods as natural pressures. But most high-mark IB ESS responses make the key point: human activity often amplifies natural degradation processes.

A drought becomes a crisis when vegetation cover was already removed. A storm becomes topsoil loss when fields were left bare. A dryland becomes desertified when grazing pressure prevents recovery.

This is also where systems thinking shows up. If you want a model for writing these links, the blog post How Do Humans Impact Ecosystems in ESS? (2026 First Assessment) is a strong companion.

How to study soil degradation efficiently on RevisionDojo

If you’re revising IB ESS under time pressure, treat soil degradation as an exam skill, not a reading task:

• Use Soil degradation and conservation notes for definitions and mechanisms.

• Drill timed responses with the 5.3 Questionbank.

• Build retrieval with Flashcards and quick summaries (RevisionDojo Flashcards and Cheatsheets).

• Use AI Chat to test yourself: “Explain salinization as a feedback loop” or “Give a 6-mark erosion answer with a case study.”

• When you write, use Grading tools to check if your response actually hits the command term.

If you want a wider map of how soil fits the 2026 course, read IB ESS: How Soil Is Covered in the 2026 Syllabus.

Closing: soil degradation is slow, but your progress doesn’t have to be

The main causes of soil degradation in IB ESS are easy to list: erosion, salinization, nutrient depletion, desertification, pollution, and compaction. The exam challenge is explaining each one as a system story: a pressure changes transfers and storages, then the consequences ripple into food production and sustainability.

If you want to revise IB ESS with less stress and more momentum, RevisionDojo is built for this exact loop: Study Notes for clarity, Flashcards for recall, Questionbank for exam practice, AI Chat for instant testing, and Grading tools to sharpen your responses. Add Predicted Papers, Mock Exams, and the Coursework Library when you’re ready to simulate the real thing, and Tutors when you want personalised feedback.

When soil degrades, it’s usually because small choices repeated over time became a big outcome. Your revision works the same way, in the opposite direction.