IB ESS 2.3-L2 When does a forest become a carbon source? Lesson Walkthrough

This 60-minute IB ESS lesson is for SL and HL students on the first-assessment-2026 course.

A forest can hold much carbon while its annual balance changes. Students use staged carbon accounts to distinguish sequestration from existing storage, compare a young forest, a balanced mature-forest model and a disturbed forest, and test how harvest and soil management change a claim. A management recommendation must state what is counted, how long carbon remains stored and what further evidence is needed.

The teacher walkthrough includes preparation, a five-phase sequence, prompts, response guidance and an optional extension. Teacher-only response guidance is separate from the student reproducibles; no separate answer-key file is supplied.

Included: editable teacher walkthrough in Word and matching 15-page PDF; editable student reproducibles in Word and matching 6-page PDF.

The student resources also appear in the teacher PDF appendix. Fictional cases and model data are identified where used; supplied datasets and simulations are not completed fieldwork. Follow the walkthrough’s preparation and safeguards for practical or digital options.

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