Chapter 3 The Big Picture: Systems of Change Botkin & Keller Environmental Science 5/e

Chapter 3Chapter 3The Big Picture: The Big Picture: Systems of ChangeSystems of Change

Botkin & KellerEnvironmental Science 5/e

Systems and FeedbackSystems and Feedback

System:System:A set of components or parts that function A set of components or parts that function

together to act as a whole.together to act as a whole.

Open System:Open System:Not generally contained within boundariesNot generally contained within boundariesSome energy or material moves into or out Some energy or material moves into or out

of the systemof the system

Closed System:Closed System:No energy movement into or out of the No energy movement into or out of the

systemsystemBotkin & KellerEnvironmental Science 5/e

Systems and FeedbackSystems and Feedback

FeedbackFeedback Occurs when the output of the system also Occurs when the output of the system also

serves as an input, leading to further changes serves as an input, leading to further changes in the systemin the system

Negative FeedbackNegative Feedback Occurs when the system’s response is in the Occurs when the system’s response is in the

opposite direction of the outputopposite direction of the output Self-regulatingSelf-regulating

Positive FeedbackPositive Feedback Occurs when an increase in output leads to a Occurs when an increase in output leads to a

further increase in outputfurther increase in outputBotkin & KellerEnvironmental Science 5/e


Fig 3.6

© 2005 John Wiley and Sons Publishers



Fig 3.8


Exponential GrowthExponential Growth

Exponential growth:Exponential growth:Growth occurs at a constant rate per time Growth occurs at a constant rate per time

periodperiod Equation to describe exponential growth is:Equation to describe exponential growth is:

Doubling timeDoubling timeThe time necessary for the quantity being The time necessary for the quantity being

measured to double.measured to double.Approximately equal to 70 divided by the Approximately equal to 70 divided by the

annual percentage growth rateannual percentage growth rateBotkin & KellerEnvironmental Science 5/e

Environmental UnityEnvironmental Unity

Environmental unity:Environmental unity:It is impossible to change only one It is impossible to change only one

thing; everything affects everything thing; everything affects everything else.else.


UniformitarianismUniformitarianism

Uniformitarianism:Uniformitarianism:The principle that processes that The principle that processes that

operate today operated in the past.operate today operated in the past.Observations of processes today can Observations of processes today can

explain events that occurred in the explain events that occurred in the past and leave evidencepast and leave evidence

““The present is the key to the past.”The present is the key to the past.”


Changes and Equilibrium in Changes and Equilibrium in Systems Systems

Steady state:Steady state:A dynamic equilibriumA dynamic equilibriumMaterial or energy is entering and Material or energy is entering and

leaving the system in equal amountsleaving the system in equal amountsOpposing processes occur at equal Opposing processes occur at equal

ratesrates



Fig 3.12


Changes and Equilibrium in Changes and Equilibrium in SystemsSystems

Average residence time:Average residence time:The time it takes for a given part of The time it takes for a given part of

the total reservoir of a particular the total reservoir of a particular material to be cycled through the material to be cycled through the systemsystem

The equation for average residence The equation for average residence time is:time is:

ART = ART = S/FS/F



Fig 3.13


Earth as a Living Earth as a Living SystemSystem

Biota:Biota: All the organisms of all species living in an All the organisms of all species living in an

area or region up to and including the area or region up to and including the biospherebiosphere

Abiotic: All non-living elements of an ecosystemAbiotic: All non-living elements of an ecosystem

Biosphere:Biosphere:

1.1. That part of a planet where life existsThat part of a planet where life exists

2.2. The planetary system that includes and The planetary system that includes and sustains lifesustains life


EcosystemEcosystem

Ecosystem:Ecosystem:A community of organisms and its A community of organisms and its

local nonliving environment in which local nonliving environment in which matter (chemical elements) cycles matter (chemical elements) cycles and energy flows.and energy flows.

Sustained life on Earth is a Sustained life on Earth is a characteristic of ecosystemscharacteristic of ecosystems

Can be natural or artificialCan be natural or artificial


EcosystemsEcosystems

The Gaia Hypothesis:The Gaia Hypothesis: Named for Gaia, the Greek goddess Mother Named for Gaia, the Greek goddess Mother

EarthEarth States that the surface environment of the States that the surface environment of the

Earth, with respect to such factors as theEarth, with respect to such factors as the atmospheric composition of gasesatmospheric composition of gases acidity-alkalinity of watersacidity-alkalinity of waters Surface temperatureSurface temperatureare actively regulated by the sensing, are actively regulated by the sensing,

growth, metabolism and other activities of growth, metabolism and other activities of the biota.the biota.

Or, life manipulates life the environment for Or, life manipulates life the environment for the maintenance of life.the maintenance of life.


Why Solving Environmental Why Solving Environmental Problems Is Often DifficultProblems Is Often Difficult

1.1. Exponential growthExponential growth• The consequences of exponential growth and its The consequences of exponential growth and its

accompanying positive feedback can be dramaticaccompanying positive feedback can be dramatic

2.2. Lag timeLag time• The time between a stimulus and the response of The time between a stimulus and the response of

a systema system• If there is a long delay between stimulus and If there is a long delay between stimulus and

response, then the resulting changes are much response, then the resulting changes are much more difficult to recognize.more difficult to recognize.

3.3. Irreversible consequencesIrreversible consequences• Consequences that may not be easily rectified on Consequences that may not be easily rectified on

a human scale of decades or a few hundred a human scale of decades or a few hundred years.years.



Fig 3.14


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Chapter 3 The Big Picture: Systems of Change Botkin & Keller Environmental Science 5/e