SL and HL: Subtopic 1.2 Systems: Greater diversity and larger storages increase a system’s resilience, its ability to avoid tipping points and maintain stability. Diversity provides alternative ways for the system to function, while large storages buffer change and create time lags.
How the Mechanism Works
A diverse system has more components and pathways. If one component is damaged, another may perform a function, so the system is less likely to collapse. Several pollinator species may maintain pollination if one species declines.
A storage is a stock of matter or energy within a system; in ESS systems diagrams, it is represented by a rectangular box. Large storages can absorb disturbances without an immediate major shift. A large lake may dilute a limited pollutant input better than a small pond, although continued pollution can still push it towards a tipping point.
| System characteristic | Effect on resilience | Mechanism |
|---|---|---|
| High diversity | Usually increases resilience | Alternative pathways and functional overlap |
| Low diversity | Usually reduces resilience | Greater dependence on each component |
| Large storage | Usually increases resilience | Buffers disturbance and delays response |
| Small or depleted storage | Usually reduces resilience | Faster, proportionally larger change |
The Aral Sea illustrates storage depletion. River diversion reduced its water storage; salinity rose, biodiversity declined and fishing communities lost livelihoods. Human activity weakened ecological and social resilience, creating an environmental justice issue because local communities bore costs.
A common misconception is that a large storage makes a system permanently safe. It only provides a buffer: persistent inputs or losses can overwhelm it, trigger positive feedback, and shift the system to a new equilibrium.
Exam Technique
For an explain question, give this cause-and-effect chain: diversity provides alternatives; larger storages buffer disturbance; both reduce the likelihood of crossing a tipping point. Use a named example and precise systems terminology rather than saying the system is “stronger.”