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.
