1. The Big Picture: Systems of Change
Chapter 4
The Big Picture:
Systems of Change
Botkin & Keller
Environmental Science 5/e

2. Environmental Science 5/e
Systems and Feedback
System:
A set of components or parts that function together to act as a whole.
Open System:
Not generally contained within boundaries
Some energy or material moves into or out of the system
Closed System:
No energy or material moves into or out of the system
Botkin & Keller
Environmental Science 5/e

3. Environmental Science 5/e
Systems and Feedback
Feedback
Occurs when the output of the system also serves as an input, leading to further changes in the system
Negative Feedback
Occurs when the system’s response is in the opposite direction of the output
Self-regulating
Positive Feedback
Occurs when an increase in output leads to a further increase in output
Botkin & Keller
Environmental Science 5/e

4. Environmental Science 5/e
Botkin & Keller
Environmental Science 5/e
© 2008 John Wiley and Sons Publishers

5. Environmental Science 5/e
Botkin & Keller
Environmental Science 5/e
© 2008 John Wiley and Sons Publishers

6. Environmental Science 5/e
Exponential Growth
Exponential growth:
Growth occurs at a constant rate per time period
Equation to describe exponential growth is:
Doubling time
The time necessary for the quantity being measured to double.
Approximately equal to 70 divided by the annual percentage growth rate
Botkin & Keller
Environmental Science 5/e

7. Environmental Science 5/e
Environmental Unity
Environmental unity:
It is impossible to change only one thing; everything affects everything else.
Aspects of natural environment are closely linked
Urban and natural environments
Botkin & Keller
Environmental Science 5/e

8. Uniformitarianism Uniformitarianism:
The principle that processes that operate today operated in the past.
Observations of processes today can explain events that occurred in the past and leave evidence
“The present is the key to the past.”
Botkin & Keller
Environmental Science 5/e

9. Changes and Equilibrium in Systems
Steady state:
A dynamic equilibrium
Material or energy is entering and leaving the system in equal amounts
Opposing processes occur at equal rates
Botkin & Keller
Environmental Science 5/e

10. Environmental Science 5/e
Botkin & Keller
Environmental Science 5/e
© 2008 John Wiley and Sons Publishers

11. Changes and Equilibrium in Systems
Average residence time:
The time it takes for a given part of the total reservoir of a particular material to be cycled through the system
The equation for average residence time is:
ART = S/F
-- Important implications for environmental systems
--Input (causes); output (responses)
Botkin & Keller
Environmental Science 5/e

12. Environmental Science 5/e
Average residence time has important implication for environmental systems.
A system such as a small lake with an inlet and an outlet and a high transfer rate of water has a short residence time for water
(Working It Out 3.2, pg. 44)
Botkin & Keller
Environmental Science 5/e
© 2008 John Wiley and Sons Publishers

13. Earth as a Living System
Biota:
All the organisms of all species living in an area or region up to and including the biosphere
Biosphere:
That part of a planet where life exists
The planetary system that includes and sustains life
Botkin & Keller
Environmental Science 5/e

14. Environmental Science 5/e
Ecosystem
Ecosystem:
A community of organisms and its local nonliving environment in which matter (chemical elements) cycles and energy flows.
Sustained life on Earth is a characteristic of ecosystems
Can be natural or artificial
Botkin & Keller
Environmental Science 5/e

15. Environmental Science 5/e
Ecosystems
The Gaia Hypothesis:
Named for Gaia, the Greek goddess Mother Earth
States that the surface environment of the Earth, with respect to such factors as the
atmospheric composition of gases
acidity-alkalinity of waters
Surface temperature
are actively regulated by the sensing, growth, metabolism and other activities of the biota.
Or, life manipulates the environment for the maintenance of life.
Botkin & Keller
Environmental Science 5/e

16. Why Solving Environmental Problems Is Often Difficult
Exponential growth
The consequences of exponential growth and its accompanying positive feedback can be dramatic
Lag time
The time between a stimulus and the response of a system
If there is a long delay between stimulus and response, then the resulting changes are much more difficult to recognize.
Irreversible consequences
Consequences that may not be easily rectified on a human scale of decades or a few hundred years.
Botkin & Keller
Environmental Science 5/e

17. Environmental Science 5/e
The concept of overshoot, illustrating the influence of exponential growth, lag time, and collapse on carrying capacity
Botkin & Keller
Environmental Science 5/e
© 2008 John Wiley and Sons Publishers