Ecosystem stability depends on continuing energy input, nutrient recycling, biological diversity, and abiotic conditions that do not exceed species tolerances.
Coverage 2019–2023 · Updated 16 Jul 2026
Long-term ecosystem stability requires continuing energy supply, nutrient recycling, genetic diversity and climatic variables within organismal tolerance limits.
| Requirement | Why it supports stability |
|---|---|
| Energy supply, usually sunlight | Maintains primary production and food-web energy flow |
| Nutrient recycling | Returns finite chemical elements from waste and dead biomass to producers |
| Genetic diversity | Provides variation that can support population survival under disease or change |
| Climate within tolerance limits | Keeps temperature, precipitation and insolation compatible with resident species |
If prolonged drought pushes precipitation outside tree tolerances, producer biomass falls and both energy input and habitat complexity decline.
The requirements interact; meeting one cannot compensate indefinitely for failure of another.
This objective is assessed through structured response, commonly using Outline / Describe.
Outline / Describe
Build the answer around this relationship: Energy must continually enter ecosystems because it is transferred and lost rather than recycled.
Treating sustainability as a list of organisms only, without explaining energy input or nutrient recycling.
Representative question
Outline the features of ecosystems that make them sustainable.
Core D4.2 is secure when students can judge whether a system is being stabilized or pushed toward change. The route is: identify the stability support or disturbance, explain the mechanism, and state the ecosystem consequence using evidence.
Core transfer questions ask students to explain why an ecosystem remains stable or why a disturbance pushes it toward change. Strong answers do not list threats; they explain mechanisms such as lost rainfall recycling, trophic cascade, overharvest, nutrient enrichment, toxin biomagnification, plastic movement, or restoration through rewilding.
