Chapter 3: The Big Picture: Systems of Change

Basic Systems Concept System System Set of components or parts that function together to act as a whole Set of components or parts that function together to act as a whole Respond to inputs and outputs Respond to inputs and outputs Exs: cell, body, city, river Exs: cell, body, city, river Two general types of systems Two general types of systems Open system - some energy or material moves into or out of system Open system - some energy or material moves into or out of system Closed system - no such movements take place Closed system - no such movements take place

Basic Systems Concept Static System Static System Fixed condition; system stays in that condition Fixed condition; system stays in that condition

Basic Systems Concept Dynamic System Dynamic System Changes (often continually) over time Changes (often continually) over time

Basic Systems Concept Classical System Classical System Has a constant condition, and if disturbed, it will return to that condition once the disturbance is gone Has a constant condition, and if disturbed, it will return to that condition once the disturbance is gone

Basic Systems Concept Dynamic Equilibrium Dynamic Equilibrium The steady state that all natural systems move towards without influence of people The steady state that all natural systems move towards without influence of people Seldom attained or maintained very long Seldom attained or maintained very long

Basic Systems Concept Average Residence Time Average Residence Time How long, on average, a quantity of something will remain in a reservoir of a system How long, on average, a quantity of something will remain in a reservoir of a system

Feedback Feedback- when one part of the system changes Feedback- when one part of the system changes Those changes affect another part of the system Those changes affect another part of the system Which affects the first change Which affects the first change Negative feedback- an increase in output leads to a later decrease Negative feedback- an increase in output leads to a later decrease Self-regulating, or stabilizing Self-regulating, or stabilizing

Feedback Positive feedback- an increase in output leads to a further increase in the output Positive feedback- an increase in output leads to a further increase in the output Destabilizing Destabilizing Environmental damage can be especially serious when peoples use of the environment leads to positive feedback Environmental damage can be especially serious when peoples use of the environment leads to positive feedback

Positive Feedback

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

Stability A stable system is one that A stable system is one that Has a condition that it remains in unless disturbed 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 Condition that it returns to if disturbed from it and the cause of the disturbance stops

Exponential Growth Growth occurring at a constant rate Growth occurring at a constant rate Plotted on a graph will form a J shaped curve Plotted on a graph will form a J shaped curve

Exponential Growth (EG) Calculating EG involves two related factors Calculating EG involves two related factors Rate of growth measured as a % Rate of growth measured as a % Doubling time in years Doubling time in years Time necessary for the quantity being measured to double Time necessary for the quantity being measured to double EG is positive feedback and incompatible w/ sustainability EG is positive feedback and incompatible w/ sustainability

Logistic Growth The carrying capacity of a population is reached or approached, based on environmental factors The carrying capacity of a population is reached or approached, based on environmental factors Plotted it will form a lazy S-shaped curve Plotted it will form a lazy S-shaped curve

Overshoot and Collapse

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

Uniformitarianism Suggested by Suggested by James Hutton James Hutton Father of geology Father of geology The geological and biological processes presently forming and modifying Earth are the same now as they were in the past, and vice versa The geological and biological processes presently forming and modifying Earth are the same now as they were in the past, and vice versa Present is the key to the past; the past is the key to the future Present is the key to the past; the past is the key to the future

Earth as a System Gaia Hypothesis Gaia Hypothesis Life manipulates the environment for the maintenance of life Life manipulates the environment for the maintenance of life Planet capable of physiological self-regulation Planet capable of physiological self-regulation Really a series of hypotheses Really a series of hypotheses Life has greatly affected the planetary environment Life has greatly affected the planetary environment Life has altered Earth’s environment in ways that have allowed it to persist Life has altered Earth’s environment in ways that have allowed it to persist