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.

Systems of Change

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.

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.

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.

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

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

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.

Positive Feedback

Positive feedback loop• Exponential growth of population – more

individuals lead to increased number of births

Negative feedback loop• Temperature regulation in humans –

increased temperature leads to decrease in temperature by sweating

Feedback

• Some situations involve both + and – feedback.

• Human pop in large cities.

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.

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

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

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

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.

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.

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.