IB Environmental systems and societies 1.2E Emergent Properties Notes

The whole is greater than the sum of its parts

1. Emergent properties are new outcomes that arise from interactions among the parts of a system.
   1. Individual elements may behave predictably, yet their interactions produce behaviour no single part shows alone.
2. They cannot be predicted from the parts in isolation.
3. They occur at every level of organization, from molecules to ecosystems to global climate systems.

Key characteristics define an emergent property

1. Unpredictable from components alone: outcomes cannot be deduced by analysing isolated parts.
2. Result of interactions: they arise from relationships among biotic and abiotic elements.
3. System-level behaviour: they are observable only at a larger scale, such as population or ecosystem.
4. Dynamic: they can change over time as conditions or feedback shift.
5. Often stabilizing: many emergent processes help systems resist disturbance.

Emergence appears at every scale

Predator-prey oscillations

1. Predator and prey populations fluctuate in linked cycles over time.
2. The oscillation is a property of the interaction, which neither species shows in isolation.

The feedback mechanism behind these oscillations is covered in 1.2B.

Trophic cascades

1. A change in one trophic level ripples through the levels below it.
   1. The cascade is an emergent property of the food web, altering energy flow and species composition.

Removing one part can reshape the whole

Urban heat islands

1. Cities run hotter than nearby countryside because of interactions between built structures, materials, and weather.
   1. Concrete and asphalt absorb more heat than vegetation, and human activity adds still more.

Global climate patterns

1. Climate behaviour emerges from the interaction of temperature, ocean currents, and atmospheric circulation.
2. Patterns such as El Niño, La Niña, and monsoon cycles arise from these combined effects.
   1. No single variable, such as temperature or current, explains these oscillations alone.