3.2.3—Invasive alien species
- Syllabus
- First assessment 2026
- Objective
- 3.2.3
- Level
- HL
Trace an Alien Species from Arrival to Impact
Alien means outside its native range; invasive means the introduced population spreads and causes harm.
Follow arrival → release from controls → increase → impact mechanism → targeted management. Non-native status alone does not prove harm.
Introduced grey squirrels expand, compete with red squirrels and carry squirrelpox; control and habitat refuges target those pathways.
Harmful spread and a demonstrated ecological mechanism are also required.
Do not manage every non-native species identically; identify actual spread, harm and feasible intervention.