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  1. Welcome! • Pick up your journal from the table. • Pick up Chapter 3 reading questions (next to journals) • Place timeline on table next to journals. • Check on your seeds. Set up a data table in your notebook (remember to title it!) and record any data. We will be collecting data for 3 days. Consider using both count and measurement data. • Check board for HW and write down in planner.

  2. Systems of Change

  3. 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.

  4. 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.

  5. Environmental Unity: An Urban Example • Many midwestern US cities (i.e. Chicago) have had a shift in land use • Forest or ag 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.

  6. Environmental Unity: A Forest Example • Forest, stream and fish in the Pacific Northwest • Wood debris form and maintain pool environments in small stream. • Provide rearing habitat for young salmon • Formerly removed because thought to block fish migration • Studying relations between physical and biological systems at the heart of environmental science

  7. Feedback Loops • A feedback loop occurs when an output of a system is fed back as an input • Two kinds of feedback loops • Positive • Negative

  8. Feedback • Positive feedback- an increase in output leads to a further increase in the output. • Destabilizing • Environmental damage can be especially serious when people’s use of the environment leads to positive feedback.

  9. Positive Feedback

  10. Positive feedback loop • Exponential growth of population – more individuals lead to increased number of births

  11. Negative feedback loop • Temperature regulation in humans – increased temperature leads to decrease in temperature by sweating

  12. Feedback • Some situations involve both + and – feedback. • Human pop in large cities.

  13. 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.

  14. Complex systems • Time lags – change in a system leads to other changes after a delay – lung cancer • Resistance to change – built in resistance – political, economic • Synergy-when two or more processes interact so that the combined effect is greater • Chaos – unpredictable behavior in a system

  15. Synergy and Chaos • Synergy occurs when two or more processes interact so the combined effect is greater than the sum of the separate effects • Grapefruit and Statins • Chaos occurs in a system when there is no pattern and it never repeats itself • Noise versus Music

  16. Gaia hypothesis • The hypothesis states that life manipulates the environment for the maintenance of life. • Planet capable of physiological self-regulation • Really a series of hypotheses • Life has greatly affected the planetary environment • Life has altered Earth’s enviro in ways that have allowed it to persist

  17. Why Solving Environmental Problems Is Often Difficult • 1. Exponential growth • The consequences of EG and its positive feedback can be dramatic, leading to incredible increases of what is being evaluated or measured.

  18. Why Solving Environmental Problems Is Often Difficult • 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.

  19. Why Solving Environmental Problems Is Often Difficult • 3. Irreversible consequences • Consequences that may not be easily rectified on a human scale of decades or a few hundred years.