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Systems Science and Sustainability (Physical Systems). Oct. 13, 2008 Jeff Fletcher. Plan. Discuss Systems and Systems Science Identify Key Systems Ideas Use examples from Earth Systems Focus today on natural physical systems rather than social systems

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Systems science and sustainability physical systems

Systems Science and Sustainability(Physical Systems)

Oct. 13, 2008

Jeff Fletcher

Systems science and sustainability physical systems


  • Discuss Systems and Systems Science

  • Identify Key Systems Ideas

    • Use examples from Earth Systems

    • Focus today on natural physical systems rather than social systems

    • Other systems ideas are more relevant to social systems (later terms)



  • Sustainability involves complex and interrelated issues

    • e.g., Climate change involves multiple complex systems (both natural and social)

    • e.g., Population control involves multiple complex systems (both natural and social)

  • So what do we know about systems that might give us a framework for more effectively addressing Sustainability?

What is a system

What is a System?

  • Consider an ecosystem and economic system: what is similar? Why are they both called systems?

  • Why might it be useful to focus on their similar “system-ness” rather than on their uniqueness?



  • Comprised of:

    • Elements

      • Ecosystem and Economic system examples?

    • Interactions or relations

      • Ecosystem and Economic system examples?

      • A common relation between systems is hierarchical

        • subsystems, supra-systems

        • Consider some earth systems

  • Other ideas

    • order vs. disorder, order is constraint on relations

      • relations describe structure vs. total disorder (entropy)

    • system and environment

      • boundaries define systems

What is systems science

What is Systems Science?

  • Consider flocking birds, schooling fish, a group of friends walking together

    • ornithologist, ichthyologist, sociologist

  • Mario Bunge “Stuff-free science”

  • How is knowledge normally grouped at a University?

    • System Science not as abstract as math and philosophy

    • But more abstract (general) than individual disciplines

  • Systems Science emphasizes theories that cut across disciplines

    • Game Theory, Evolution Theory, Information Theory, Network Theory, Chaos Theory, Complexity Theory, etc

  • Interested in addressing real-world, complicated problems, from a multidisciplinary perspective

Key ideas about systems

Key Ideas About Systems

  • What makes a system?

    • Elements and Relations

    • order vs. disorder

    • system vs. environment

  • Systems States and Dynamics

    • Equilibria, Stability

      • Positive and Negative Feedbacks

    • Non-linear dynamics

      • Chaos Theory, Catastrophe Theory

    • Emergence

    • Structure

      • Open vs. Closed

      • Matter, Energy, Information

Systems can be in different states

Systems can be in different states

  • For instance, temperature or composition of atmospheric system

  • How systems change states over time is called dynamics

  • Equilibria

    • Stable vs. Unstable

    • Static vs. Dynamic

      • Example of day length at equator vs. day length elsewhere

    • Positive and Negative Feedbacks (aphids)

      • Exponential growth example of + feedback

      • Homeostasis example of - feedback

Complex systems yield surprises

Complex Systems Yield Surprises

  • Most models of systems are linear

    • Change in state predicted to be proportional to change in inputs

  • Most real and complex systems are non-linear

    • Systems with feedback are often unpredictable

    • Small causes can have big effects

      • Butterfly effect from Chaos theory

      • Catastrophe theory: state is not reversible by reversing cause

    • Current financial crisis is great example

  • Emergence

Examples from atmosphere

Examples from Atmosphere

  • Is CO2 effect proportional to its abundance in atmosphere?

    • What proportion is CO2?

      • Caution in reading graphs

      • What is ppm in percent?

    • nitrogen (78%), oxygen (21%) and argon (.93%) = 99.93% of atmosphere!

  • Methane also has disproportionate effects

  • Ozone hole: example of unintended consequences and irreversibility (video)

    • Big hole until 2017, then hole will start to shrink; back to 1980 level in year 2070!

    • Example of not reversible, directionality

Water vapor in atmosphere

Water Vapor in Atmosphere

  • Also a small proportion of atmosphere

  • Effect is being debated:

    • What would be example of positive feedback with water vapor and global warming?

    • What would be example of negative feedback?

Earth relatively closed system to matter

Earth Relatively Closed System to Matter

  • We don’t get any more atoms here on earth

    • We keep reusing the Hydrogen, Nitrogen, Oxygen, and Carbon atoms we have

    • Nature’s Recycling

    • Structure of these systems varies

      • N critical to proteins in living organisms and abundant in atmosphere, but mostly unavailable

        • Depends on symbiotic relationship in plants with bacteria that “fix” nitrogen

      • O part of H20, C02, Carbohydrates (systems interconnected)

        • Bodies burn carbohydrates -- Cn(H20)n

        • (e.g. glucose C6H12O6 + 6O2 <=> 6CO2 + 6H20 + Energy)

        • Plants can do this backwards with sun for E!

        • Similar to burning hydrocarbons (only C + H, i.e. methane=natural gas) CH4 + 202 = CO2 + 2H20 + energy

      • C lots of it, but relatively little of it is cycling in atmosphere

        • Most of the carbon is stored in geologic deposits - carbonate rocks, petroleum, and coal - formed from the burial and compaction of dead organic matter on sea bottoms. The carbon in these deposits is normally released by rock weathering.

        • Extraction and burning of fossil fuels alters this system

Atmosphere is relatively flat systems not much hierarchy

Atmosphere is Relatively Flat Systems (not much hierarchy)

  • Air molecules are very small compared to space between them

  • Can treat them as all the same (Ideal Gas Assumption)

    • A Linear relationship holds (roughly) for earth’s atmospheric temperatures and pressures

    • PV = nRT

    • Caesar’s Last Breath

Energy and heat

Energy and Heat

  • Earth is an open system to Energy

    • ability to do work

  • Potential, Kinetic, Heat Energy

    • Heat: Radiation

      • electromagnetic waves (even through vacuum)

      • Sunlight, microwaves, infrared

    • Heat: Conduction

      • molecular vibrations in solids spreads to neighbors

    • Heat: Convection

      • Molecules move in gases and liquids—collide and spread their kinetic energy



  • Second Law of Thermodynamics:

    • entropy (disorder) increases (or at best stays the same when cycles of work are done (for closed systems)

  • Order necessary to maintain system’s integrity

    • comes from energy flow into system (not closed), e.g. sunlight on earth

    • Overall Entropy is increasing in the Universe, but there are “back eddies” of order driven by energy input (e.g. life on earth)

Matter energy information

Matter, Energy, Information

  • Matter can be seen as acted upon by energy

  • But understanding matter and energy relationship is not enough

  • Information can organize matter and energy

    • Acorn Example

More socially relevant systems ideas

More Socially Relevant Systems Ideas

  • Optimization

    • Local vs. global

    • Cannot optimize system and its subsystems at the same time

    • Tension between systems and subsystems

    • Examples

      • You and your liver

      • Efficient country and local autonomy/control

  • Game Theory

    • Tragedy of the Commons

    • Prisoner’s Dilemma, Chicken

    • Discounting Future

    • Maximin, Nash Equilibrium, Pareto Optimality



  • Another way to think about systems:

    • Complex systems have inherent problems that are affected by their systems characteristics

  • Characteristics worth thinking about include:

    • Dynamics (equilibria, +/- feedbacks, non-linearity, emergence)

    • Structure of relationships

      • Open vs closed (matter, energy, entrpy)

      • Degree of hierarchy

      • Hierarchy of Matter, energy, information

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