Resilience is a system’s tendency to avoid tipping points, maintain stability, and remain within its existing equilibrium when disturbed. In IB ESS Subtopic 1.2 Systems, resilience generally increases with greater diversity, larger storages, and effective stabilizing feedback. This is core content for both SL and HL.
How resilience works
A resilient system can absorb a disturbance without shifting into a different equilibrium. An ecosystem may survive drought by retaining enough organisms, water, nutrients, and reproductive capacity to recover.
Negative feedback loops increase resilience because they counteract change and return a system toward its previous equilibrium.
By contrast, positive feedback loops amplify disturbances and can drive a system toward a tipping point. Once that threshold is crossed, a small additional change may cause a large and potentially difficult-to-reverse regime shift.
| Factor | How it affects resilience | Example |
|---|---|---|
| Diversity | Provides alternative species or components that can perform similar functions if one is lost | Several pollinator species reduce dependence on one species |
| Large storages | Provide reserves that buffer short-term change and create time lags | Stored soil water reduces the immediate impact of drought |
| Negative feedback | Counteracts deviation and helps maintain stable equilibrium | Predation regulates prey populations |
| Human activity | Can reduce diversity and storages, weakening resilience | Deforestation removes biomass, soil protection, and water storage |
The Amazon rainforest illustrates these interactions. Deforestation reduces biodiversity and vegetation storage, while lower evapotranspiration can reduce regional rainfall. This may strengthen drying and fire feedbacks, increasing tipping-point risk. The consequences also affect Indigenous peoples and other forest-dependent communities, so resilience has ecological and environmental justice dimensions.
Exam technique
For an explain question, give a causal chain: factor, mechanism, and effect on equilibrium. In a systems diagram, show storages as boxes, flows as arrows, and identify each loop as stabilizing or amplifying. Avoid the misconception that resilience means no change resilient systems may change without shifting into a new equilibrium.