Understanding Complex Systems and Environmental Unity

1. Chapter 3: How to Think About Complex Systems

2. Systems • A system is a set of components or parts that function together to act as a whole. • E.g. Body, city, river • Open system- some energy or material moves into or out of system. • Closed system- no such movements take place.

5. Stability • A stable system is one that • Has a condition that it remains in unless disturbed. • Condition that it returns to if disturbed from it and the cause of the disturbance stops. • Whether this is desirable depends on the system and potential changes.

6. Environmental Unity • It is impossible to change only one thing • Everything effects everything else • Earth and its ecosystems are complex entities in which any action may have several or many effects.

7. Environmental Unity: An Urban Example • Many mid-western US cities (i.e. Chicago) have had a shift in land use • Forest or agricultural land to urban development • Construction increases runoff and soil erosion • Effects river channels and flood hazard • After construction sediment load decreases but runoff still increases • Thus land-use changes set off a series of changes which can trigger additional changes.

8. Uniformitarianism • The physical and biological processes presently forming and modifying Earth are the same now as they were in the past. • A study of past and present processes is key to the future.

10. Changes and Equilibrium in Systems

11. Earth and Life • Earth formed 4.6 billion years ago • Life began on Earth 3.5 billion years ago • Since life’s emergence many organisms have evolved, flourished, and become extinct. • Humans to may some day become extinct. • Human activities increase and decrease the magnitude and frequency of natural processes. • Leading to many human caused extinctions.

12. Earth as a Living System • Biota- all living things within a given area • Biosphere- region of Earth where life exists • Also includes the system that sustains life • All living things require energy and materials. • Energy from the sun and interior of Earth • Materials recycles through the system

13. Ecosystem • A community of organisms and its local nonliving environment in which matter cycles and energy flows. • Can be applied to different scales • Puddle to forest to planet • What is common to all is not physical structure but existence of processes • Can be natural or artificial

14. Why Solving Envt. Problems Is Often Difficult? • 1. Exponential growth • Dramatic consequences, leading to incredible increases. • 2. Lag time • The time between a stimulus and the response of a system. • Long lag time or delays may lead to overshot and collapse • Going beyond the carry capacity can lead to a collapse of a population. • 3. Irreversible consequences • Consequences that may not be easily rectified on a human scale of decades or a few hundred years.