This is a working draft for Leslie's review. The dependency edges below are a first pass — the diagram and the prerequisite table are the parts to check hardest, since they drive hold-vs-advance decisions.
The course map shows the eight units as a spine — ecosystems first, sustainability and policy last. But the real prerequisite structure isn't a straight line: it's a directed graph. Environmental Science is more strictly cumulative than most subjects — biodiversity needs energy flow, the nutrient cycles build on the living communities that move them, and the water and climate units need both the cycles and the human pressures that disrupt them. A weak concept early doesn't just lower one grade, it cascades into everything downstream that needs it. This page is the map a guide uses to find the concept that's actually blocking a stuck student.
An arrow means “must be mastered first.” Units 05, 06, and 08 each pull from two upstream units — those are the cascade points where one soft prerequisite quietly breaks several later units.
Prerequisite gating
A unit unlocks when its prerequisites are mastered — demonstrated, not merely seen. "Covered in class" is not the gate; a cleared rubric is. The difference matters most at the cascade points, where a soft prerequisite quietly breaks two or three later units.
| Unit | Must have mastered first |
|---|---|
| 01 Ecosystems & Energy Flow | — (entry point) |
| 02 Biodiversity & Populations | 01 (energy flow & trophic structure set up populations) |
| 03 Biogeochemical Cycles | 02 (nutrient flow tracks the living communities that move it) |
| 04 Human Population & Resource Use | 02 (population dynamics extend to the human population) |
| 05 Water Resources & Pollution | 03 (nutrient loading drives pollution) + 04 (human demand strains water supply) |
| 06 Air, Atmosphere & Climate Change | 03 (the carbon cycle) + 05 (pollution pathways through air and water) |
| 07 Land Use, Agriculture & Waste | 05 (land use and water quality are tightly coupled) |
| 08 Sustainability & Environmental Policy | 06 (climate evidence) + 07 (land, agriculture & waste evidence) |
Gap-cascade diagnosis
When a student stalls late, the visible symptom is rarely the real problem — the broken concept is usually upstream. Trace the arrows backward. Common cascades:
| Late symptom | Upstream concept to check first |
|---|---|
| Land-use and waste-impact arguments fall apart (Unit 07) | Water systems from Unit 05 — land use and water quality run together. |
| Climate-forcing arguments don't hold together (Unit 06) | The carbon and nitrogen cycles from Unit 03 — forcing is a cycle disruption, not a standalone idea. |
| Policy cost–benefit cases stall (Unit 08) | The climate and land-use evidence from Units 06–07 the case is built on. |
| Pollutant-load interpretation goes wrong (Unit 05) | Where the nutrients come from — the biogeochemical cycles in Unit 03. |
Using the graph to plan a re-attempt
The graph turns a "not yet" into a targeted re-attempt instead of a whole-unit re-teach. When a student fails a downstream demonstration:
- Trace backward to the upstream node the symptom points to.
- Re-attempt the upstream concept first — close the gap at its source, not where it surfaced.
- Then re-run the downstream demonstration. Often it passes without any re-teaching of the downstream unit at all, because the cascade is resolved.
This is also where the integration guide matters: some environmental science concepts depend on an applied-math idea — logarithmic scales for pH and pollutant concentration, proportional reasoning for population growth and per-capita footprints — from another spoke. When the upstream environmental science node looks solid but the student still stalls, check the cross-disciplinary dependency before re-teaching the science.