Understanding Ecological Succession in IB ESS
In IB Environmental Systems & Societies (ESS), ecological succession describes the natural process by which ecosystems change and develop over time. It’s how barren or disturbed environments evolve into complex, stable communities. Succession demonstrates how ecosystems maintain resilience and stability — major concepts in IB ESS under Topic 2: Ecosystems and Ecology.
Succession shows that ecosystems are dynamic, constantly responding to environmental changes, natural disturbances, and species interactions.
The Two Main Types of Ecological Succession
1. Primary Succession: Formation of New Ecosystems
- Occurs on surfaces where no soil or life previously existed (e.g., after volcanic eruptions, glacial retreat, or on bare rock).
- Pioneer species like lichens and mosses colonize the area first. They break down rock, form soil, and create conditions suitable for new species.
- Gradually, grasses, shrubs, and trees establish, leading to a climax community — the most stable stage of ecosystem development.
Example: The formation of ecosystems on newly formed volcanic islands, such as Surtsey (Iceland), is a classic case of primary succession.
2. Secondary Succession: Recovery After Disturbance
- Occurs where an existing community has been disturbed but soil remains (e.g., after forest fires, floods, or human deforestation).
- Since soil and nutrients are already present, recovery is faster than in primary succession.
- Plants regrow, animals return, and balance gradually restores.
Example: Forest regrowth after a wildfire in California illustrates how ecosystems can recover naturally through secondary succession.
Key Stages of Ecological Succession
Ecological succession follows a predictable sequence:
- Pioneer Stage: Hardy species colonize barren areas.
- Intermediate Stage: Increased soil quality allows shrubs and small trees to grow.
- Climax Community: A mature, stable ecosystem with balanced biodiversity and nutrient cycling.
These stages reflect increasing biomass, complexity, and stability, demonstrating how ecosystems self-regulate — a key IB ESS concept of system equilibrium.
Factors Influencing Succession
- Abiotic factors: Temperature, precipitation, and soil composition determine the rate of succession.
- Biotic interactions: Competition, predation, and symbiosis shape species composition.
- Disturbances: Fires, floods, or human activities reset succession stages.
In IB ESS, understanding these interactions helps students explain resilience — an ecosystem’s ability to return to equilibrium after disturbance.
Why Ecological Succession Matters for IB ESS Students
Succession connects to multiple IB ESS themes:
- Ecosystem resilience and equilibrium
- Biodiversity and species interactions
- Human impacts on natural recovery
Students often analyze data on biomass, species diversity, and nutrient cycling to interpret succession trends in exam questions. Mastering this topic also supports understanding of ecosystem management and conservation.
Through RevisionDojo’s IB ESS course, students can study interactive succession diagrams, practice past-paper questions, and explore case studies showing ecosystem recovery after human or natural disturbance.
FAQs
What is ecological succession in IB ESS terms?
It’s the process by which ecosystems change and develop over time, moving from pioneer species to a stable climax community.
What is the difference between primary and secondary succession?
Primary succession starts on bare surfaces with no soil, while secondary succession occurs where life and soil already exist but were disturbed.
Why is succession important in environmental systems?
It demonstrates how ecosystems recover from disturbance, maintain stability, and increase biodiversity — essential for sustainability and resilience.
