Introduction
Carrying capacity is a key concept in IB Environmental Systems and Societies (ESS). For the 2026 first assessment, you are expected to understand how population growth interacts with environmental limits through different models of carrying capacity.
This topic matters because it highlights the tension between human demand for resources and the Earth’s ecological limits. It also links directly to population dynamics, sustainability, and ecological footprints—making it a frequent feature in exam questions.
Quick Start Checklist for ESS Students
When revising carrying capacity, make sure you can:
- Define carrying capacity.
- Explain the difference between exponential growth and logistic growth.
- Interpret population graphs.
- Apply carrying capacity models to human populations.
- Use case studies to illustrate the concept.
What Is Carrying Capacity?
- Carrying capacity is the maximum population size an environment can support sustainably over time.
- Determined by factors such as food, water, shelter, space, and waste absorption.
- ESS stresses that human carrying capacity is flexible—technology, trade, and culture influence it.
Carrying Capacity Models in ESS
1. Exponential Growth Model (J-Curve)
- Population grows without limits when resources are abundant.
- Produces a J-shaped curve.
- Examples: early stages of industrialization when populations expanded rapidly.
2. Logistic Growth Model (S-Curve)
- Growth slows as resources become limited.
- Produces an S-shaped curve, leveling off at carrying capacity.
- Examples: deer populations in enclosed reserves.
Applying Carrying Capacity to Humans
Unlike animals, human carrying capacity is influenced by:
- Technology: agriculture, irrigation, fertilizers.
- Trade: importation of resources.
- Culture: consumption patterns, diets, family size.
- Politics and economics: policies, governance, inequality.
This makes human carrying capacity more complex—and often controversial—compared to ecological carrying capacity for non-human species.
Case Studies for Carrying Capacity
- Easter Island: overpopulation, deforestation, and collapse of society.
- Sahel (Africa): fragile soils under pressure from population growth and overuse.
- Japan: high population density sustained through trade and technology.
Carrying Capacity in ESS Exams
Paper 1
You may be asked to interpret population graphs showing J-curves or S-curves.
Paper 2
Possible essay questions include:
- “Distinguish between exponential and logistic population growth models.”
- “Evaluate the usefulness of carrying capacity as a concept for human populations.”
Exam Tips
- Draw graphs. Even simple sketches of J-curves and S-curves can earn marks.
- Use human examples. Show how technology alters carrying capacity.
- Evaluate limitations. Carrying capacity is not fixed for humans—examiners expect you to note this.
FAQs
1. Do I need to know equations for population growth?
No, just the shape and interpretation of exponential and logistic models.
2. Is carrying capacity the same as ecological footprint?
Not exactly. Carrying capacity is about population limits, while ecological footprint measures per capita resource use. But they are closely linked.
3. Could this appear in Paper 1?
Yes. Graph interpretation questions are very common, and population models are a likely feature.
Conclusion
Carrying capacity models are essential in ESS because they show how populations interact with environmental limits. By mastering exponential and logistic growth, applying them to human populations, and supporting your answers with case studies, you’ll be ready for exam questions in the 2026 first assessment.
RevisionDojo Call to Action:
Need clear population model diagrams and practice questions? RevisionDojo provides structured ESS guides that make concepts like carrying capacity simple and exam-ready.
