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SYSTEMS THINKING

AN

ESSENTIAL SKILL FOR

UNDERSTANDING AND

MANAGING COMPLEXITY

Carl Smith

School of Agriculture and Food Science, University of Queensland (UQ)

Macquarie Island

• Situated about 1500 km south-south-east of Tasmania,

about half way between Tasmania and Antarctica

• The main island is approximately 34 km long and 5.5

km wide at its broadest point

• Around 3.5 million seabirds arrive on Macquarie Island

each year to breed and moult

Macquarie Island

Macquarie Island

• Many types of feral animals were introduced to

Macquarie Island in the 19th century, including cats, rabbits, rats and mice.

• Feral cats had a devastating effect on the native

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Macquarie Island

• So what do you think happened when the feral cats

were removed? The seabirds were saved, right?

With Cats

Without Cats

Macquarie Island

• What the management plan of Macquarie Island failed

to realise is that cats don’t just eat seabirds, they also eat rabbits, rats and mice

• The eradication of cats caused an explosion in the

rabbit, rat and mice populations on Macquarie Island, the impact of which was just as bad for seabirds as having cats on the island

• This is a classic example of policy resistance (a fix that

failed), which resulted from the failure of managers to understand the system

Rabbit Population Rabbit Births

+

+ Rabbit Birth Rate

+

Rabbit Deaths

-+

Rabbit Death Rate

+

Cat Population Cat Births

+

+ Cat Birth Rate

+

Cat Deaths

-+ Cat Death Rate

+ +

-Cat Cull + Seabird Habitat

Eaten +

R1 B1

R2 B2

B3

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Fixes that Fail

Macquarie

Island

Seabirds Lost Remove Cats

Rabbit Population Habitat

Destruction

+

-+

+ +

B

R

Delay

The Moral to this Story

(Sterman, 2000, Chapter 1)

• “When you are confronted with any complex system that has things about it that you want to fix, you cannot just step in and set about fixing them. You cannot meddle with one part of a complex system without the almost certain risk of setting off disastrous events that you hadn’t counted on in other parts. If you want to fix something, you are first obliged to understand the whole system” (biologist Lewis Thomas, 1974)

The Moral to this Story

• To understand the whole system you have to:

1. Integrate knowledge from different disciplines, i.e. be multidisciplinary

2. Understand how the interactions among system components (system structure) influence system behaviour

3. By understanding the relationship between system structure and behaviour, identify points where you can intervene to influence system behaviour whilst minimising unintended consequences

• Complex system dynamics is determined by

interactions and feedbacks among system components, not by the number of components

• The dynamics of all systems arises from the

interaction of just 2 feedback loops –positive (or

reinforcing) and negative (or balancing)

• Positive feedback loops reinforce or amplify change

while negative feedback loops balance or counteract change

The Relationship between

System Structure and Behaviour

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Positive or reinforcing feedback loops Negative or balancing feedback loops

Dynamics of Multiple-Loop Systems

B R Chickens

Eggs CrossingsRoad +

+

+

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Out of these common modes of behaviour, which one would best represent the number of people with the flu over the flu season?

Infected Population

Susceptible Population

-Recovered or Dead Population

+ Infection Rate

+

Basic Overshoot and Collapse CLD for

the Flu

Susceptible Population with

Symptoms

Recovered/Dead Population Susceptible people

becoming infected

- +

Infected people starting to show symptoms

- +

Infected people recovering or dying

- +

Disease transfer probability

+

Number of contacts between infected and susceptible people +

Probability of meeting a susceptible person +

Total Population

-+ B1

Total contacts between infected and other people

per day

Total infected population

+ +

Contacts an infected person has with other people per

day Delay time for symptoms to develop

-B2

+ Delay time for symptomatic people to

recover or die

-Population with

Symptoms

Recovered/Dead Population Susceptible people

becoming infected

- +

Infected people starting to show symptoms

- +

Infected people recovering or dying

- +

Disease transfer probability

+

Number of contacts between infected and susceptible people +

Probability of meeting a susceptible person +

Total Population

-+ B1

Total contacts between infected and other people

per day

Total infected population

+ +

Contacts an infected person has with other people per

day Delay time for symptoms to develop

-B2

+ Delay time for symptomatic people to

recover or die

-B3

R2

-B4

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Stock and Flow Structure derived

from the CLD

Simulated Behaviour of the System

(Infected population peaks at 17,500 at day 12)

Reduce contacts per infected person from

2 to 1 other person per day

(Infected population peaks at 14,500 at day 22)

Reduce chance of disease transfer due to

contact from 50% to 25%

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Reduce contacts to 1 person per day and

chance of disease transfer to 25%

(Infected population peaks at 9,500 at day 43)

• Lots!

• The livestock production system contains many

feedback loops that control its dynamics

• We are currently building a simple livestock production

model for Selayar as part of a World Bank and UQ funded project called Capturing Coral Reef and Related Ecosystem Services (CCRES)

What has Systems Thinking got

to do with Livestock Production?

• The system models we are building for CCRES aim to

simulate the interactions between society and coastal ecosystems to understand problems such as fish catch decline, mangrove loss, water pollution and food security

• Some of these interactions are caused by land use

change and land use change is influenced by crop and livestock production, as well as population growth

• The next slide represents some of the feedback loops

within the livestock production system that we are trying to model in Selayar

What has Systems Thinking got

to do with Livestock Production?

Livestock Production Demand for meat and

livestock products

+

Price of meat and livestock products

+

Population growth

+ +

Supply of meat and livestock products

+

-Household income

+

Consumption of land and water for livestock

production

+

Land and water resource available for livestock production

-+

Land and water degradation +

-+ +

-Competition with substitutes and imports

-Consumption of land and

water by population

+

-B5

+

Land and water resources available for population

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-Livestock Production Model

Livestock Demand Model

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• They essentially model balancing loops within the livestock production system that seek a dynamic equilibrium between consumption, production and price

• They also obey limits to growth, that is, livestock

production cannot exceed the carrying capacity of land and water

• Lets look at a scenario

What do these Models do?

Population grows and reaches

limits to growth

There is no change in the desired

household demand for meat

12:30 PM Wed, 16 Nov 2016

Untitled Page 1

0.00 250.00 500.00 750.00 1000.00

Weeks

1: Population 2: Houses 3: Urban land area

1

0.00 250.00 500.00 750.00 1000.00 Weeks 1: actual meat price[Cattle]

1 1 1 1

Population growth Total demand for meat

Total livestock production Meat price

2:31 PM Wed, 16 Nov 2016 Untitled

Page 1

0.00 250.00 500.00 750.00 1000.00 Weeks 1: total demand f or meat by liv estock ty pe[Cattle]

1

1 1 1

2:31 PM Wed, 16 Nov 2016

Untitled Page 1

0.00 250.00 500.00 750.00 1000.00

Weeks

1: total desired liv estoc…y by liv estock ty pe[Cattle]2: total f attening liv estock by liv estock ty pe[Cattle]

1

1 1 1

2

2 2 2

Population grows and reaches

limits to growth

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12:30 PM Wed, 16 Nov 2016 Untitled

Page 1

0.00 250.00 500.00 750.00 1000.00

Weeks

1: Population 2: Houses 3: Urban land area

1

Population growth Total demand for meat

Total livestock production Meat price

2:42 PM Wed, 16 Nov 2016 Untitled

Page 1

0.00 250.00 500.00 750.00 1000.00

Weeks 1: total demand f or meat by liv estock ty pe[Cattle]

1

0.00 250.00 500.00 750.00 1000.00

Weeks

1: total desired liv estoc…y by liv estock ty pe[Cattle]2: total f attening liv estock by liv estock ty pe[Cattle]

1

0.00 250.00 500.00 750.00 1000.00 Weeks 1: actual meat price[Cattle]

1 1 1

1

• When managing any system, understand the

relationship between system structure and system behaviour

• Use multiple sources of knowledge to develop your

understanding, i.e. be multidisciplinary

• Use your understanding of system structure to

carefully target your interventions, otherwise your cure may end up being worse than the disease

• When managing systems there is rarely a silver bullet

solution to problems, therefore multiple interventions may be needed

Figur

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