Systems Thinking
Nathaniel J. C. Libatique
A System Is
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More than the sum of
its parts
Where the rules of the
game are as important
Composed of
Elements and
Interconnections
Invested with a
Purpose
http://www.cellsignal.
com/reference/pathw
ay/Apoptosis_Overvi
ew.html
Ingredients
Collective Behavior
 Signaling and Computation
 Adaptation
Large scale networks with no central control and
simple rules give  complex collective
behavior, sophisticated signaling and
information processing and adaptation via
learning or evolution
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“A system is more than the sum of its parts. It
may exhibit adaptive, dynamic, goal-seeking,
self-preserving, and sometimes evolutionary
behavior.” (D. Meadows)
• MAFIA
• Residents in MTUs
• Sand on the road
• Apoptosis
• Trees
http://en.wikipedia.org/wiki/Corleone_crime_family
Elements vs. Interconnections
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Tree system: physical flows and
chemistry
Sunny day  lose water 
pressure drop  roots take in
more
Roots see dry soil  pressure loss
signals closing of leaf pores
Colder temperatures  nutrients
pass from leaves to trunk and
roots
Overall purpose of the tree is to
grow
Purpose of the tree is nested
within the purpose of the forest
fan.theonering.net/middleearthtours/ents.html
Nature. 2000 Nov 16;408(6810)
Feedback control of intercellular signalling in
development.
Freeman M. MRC Laboratory of Molecular Biology,
Cambridge, UK. MF1@mrc-lmb.cam.ac.uk
The intercellular communication that regulates
cell fate during animal development must be
precisely controlled to avoid dangerous errors.
How is this achieved? Recent work has
highlighted the importance of positive and
negative feedback loops in the dynamic
regulation of developmental signalling. These
feedback interactions can impart precision,
robustness and versatility to intercellular
signals. Feedback failure can cause disease.
http://www.cellsignal.com/reference/pathway/Angi
ogenesis.html
http://www.ebi.ac.uk/microarray/biology_intro.html
“The least obvious part of the system, its function
or purpose, is often the most crucial
determinant of the system behavior.” (D. Meadows)
• Purpose deduced from behavior, not necessarily
stated goals… adiabatic frog, climate change policies vs.
growth, corrupt government
• Purposes of subunits can add up to an unwanted
overall behavior! … universities, government
inflow
Stocks and Flows
stock
outflow
stock
Fossil fuel, energy efficiency, energy policies
and legislation ….
inflow
outflow
stock
cooling
Coffee
temperature
B
discrepancy
Room
temperature
The greater the temperature difference, the faster the
coffee will cool. Purpose of system is to reduce the
discrepancy to zero.
Balancing feedback: goalseeking, stabilizing,
regulating loop
Body’s
stored
energy
Metabolic
mobilization
of energy Energy
Energy
expenditure
available
for work
Coffee
intake
B
discrepancy
Desired
energy
level
Runaway Loops –
Reinforcing Feedback.
Arms race, accelerated
climate change, inflation,
erosion, epidemics
http://www.guardian.co.uk/world/2010/jan/28/human-rights-watch-hamas
Interest
added
Money in
bank
R account
Interest
rate
pg 31, Meadows
investment capital
Machines/Factories
 Goods/Services
Fraction
of
Output
invested
R
output
CO2
Product
ion
Global
Temp
+
─
R
+
Albedo
A study published in the September 7th issue
(2006) of Nature authored by Katey Walter of
the University of Alaska, and Jeff Chanton of
Florida State University reports that
greenhouse gas is escaping into the
atmosphere at a frightening rate.
Melting permafrost peatlands at Noyabrsk,
Western Siberia.
http://www.terranature.org/methaneSiberia.htm
Biomass
Global
Temp
CO2
Product
ion
R
+
Trapped
GHGs
Why Systems Surprise
 Series
of visible events fool us: a river
floods, a forest cut down, oil
discovered, market crashes.
 Interconnection between systems
structure and behavior is hidden:
interlocking stocks, flows and
feedback loops
Page 92, Thinking in Systems
Spruce budworm
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Budworm attacking spruce and fir for 400 year
cycle now (tree ring records). White pine prime
lumber
Annual DDT since 1950, still budworm
resurgence, 1980 $12.5 M in New Brunswick
Fir – most competitive, spruce next, then birch
Fir threatens monoculture, worm opens forest.
Forest System
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Fir builds up, worm’s favorite food
Budworm population increases nonlinearly
Two to three warm dry springs increase
survivability
Natural enemies cannot control worms
Drastic reduction of food supply crashes the
population!
Oscillation
Drug Supply: Goals
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Addicts - high
Enforcement Agencies - low
Pushers – not to high not too low
Citizens - Safety
Drug Supply System
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Enforcement agents cut imports at border
Drug supply goes down
Other stakeholders redouble efforts to push it
back up:
street prices go up
 addicts commit more crimes for their fix
 more profits at higher prices, suppliers use profits to
increase capital (planes boats)
 Drug supply goes up
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Resources
D. Meadows, “Thinking in Systems”, Check Google Books
http://books.google.com/books?id=JSgOSP1qklUC&printsec=fro
ntcover&dq=donella+meadows+systems+thinking&cd=1#v=o
nepage&q=&f=false
 Steven Levitt: “Why do crack dealers still live with their moms?”
http://www.youtube.com/watch?v=5UGC2nLnaes
 http://www.pioneerentrepreneurs.net/presentations/An%20Int
roduction%20to%20System%20Dynamics.html
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http://www.raczynski.com/pn/simball.htm
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Powersim constructor lite
Netlogo has a systems dynamics tool
SCICOS from Scilab also has a low level
www.simulistics.com
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