Introduction
Succession is a key ecological process in IB Environmental Systems and Societies (ESS). It explains how ecosystems develop and change over time, moving from bare ground or disturbed land to more complex, stable communities.
In the 2026 syllabus, succession is directly tied to systems thinking, as it shows how ecosystems respond to change, recover, and stabilize. Examiners often test it through diagrams, data-response questions, and essays, making it essential knowledge for Paper 1 and Paper 2.
Quick Start Checklist: Succession in ESS
- Succession = Natural change in ecosystems over time.
- Primary succession: Starts from bare surfaces (lava flows, sand dunes).
- Secondary succession: Follows disturbance (fire, deforestation, farming).
- Leads to climax communities or new stable states.
- Tested through diagrams, case studies, and application questions.
Primary vs Secondary Succession
Primary Succession
- Begins on bare, lifeless surfaces with no soil (e.g., volcanic rock, glacial retreat).
- Pioneer species (lichens, mosses) colonize first.
- Soil forms as organisms break down rock and accumulate organic matter.
- Over time, more complex species establish, leading to a climax community.
Secondary Succession
- Occurs after a disturbance (wildfire, agriculture, storm damage).
- Soil already exists, so succession is faster than primary succession.
