System Dynamics

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System Dynamics

• A simple way to look at complex situations and
  problems

Barry H. Dunn, Ph.D. Range Livestock Production
Specialist Animal and Range Sciences Dept. SDSU
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Weaning Weight
Pregnancy
Death Loss
Calving Distribution
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Genetics
Labor
Precipitation
Winter Feed
Bull/Cow Ratio
Equipment
Lbs Beef/Acre
Net Income
Buildings Facilities
Capital Investments
Ranch
Weaning Weight
Birthweight
EPDs
Pregnancy Rate
Fixed Cost
Stocking Rate
Nutrition
Cow Mature Size
Variable Cost
Calves Weaned
Calving Time
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Genetics
Labor
Precipitation
Winter Feed
Bull/Cow Ratio
Equipment
Lbs Beef/Acre
Net Income
Buildings Facilities
Capital Investments
Ranch
Weaning Weight
Birthweight
EPDs
Pregnancy Rate
Fixed Cost
Stocking Rate
Nutrition
Cow Mature Size
Variable Cost
Calves Weaned
Calving Time
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Genetics
Labor
Precipitation
Winter Feed
Bull/Cow Ratio
Equipment
Lbs Beef/Acre
Net Income
Buildings Facilities
Capital Investments
Ranch
Weaning Weight
Birthweight
EPDs
Pregnancy Rate
Fixed Cost
Stocking Rate
Nutrition
Cow Mature Size
Variable Cost
Calves Weaned
Calving Time
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Genetics
Labor
Precipitation
Winter Feed
Bull/Cow Ratio
Equipment
Lbs Beef/Acre
Net Income
Buildings Facilities
Capital Investments
Ranch
Weaning Weight
Birthweight
EPDs
Pregnancy Rate
Fixed Cost
Stocking Rate
Nutrition
Cow Mature Size
Variable Cost
Calves Weaned
Calving Time
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Genetics
Labor
Precipitation
Winter Feed
Bull/Cow Ratio
Equipment
Lbs Beef/Acre
Net Income
Buildings Facilities
Capital Investments
Ranch
Weaning Weight
Birthweight
EPDs
Pregnancy Rate
Fixed Cost
Stocking Rate
Nutrition
Cow Mature Size
Variable Cost
Calves Weaned
Calving Time
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System Dynamics

• A school of thought and body of knowledge.
• Started at MIT about 40 years ago.
• Founder, Jay Forester, grew up on a ranch in the
  Sandhills of Nebraska.
• Professional Society.
• Departments in Universities.
• Used by business and Govt.

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System Dynamics

• Used in Business
• Compac
• Ford
• BMW
• Used in Government
• Federal Reserve
• Local Governments

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System Dynamics vs. Traditional Scientific Method

• SD based on the inter-relationships in complex
  and ever changing systems.
• Basic assumption of Scientific method
• populations are normally distributed
• variables are independent of one another

What if they are not?
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Example

• Nutrition and Reproduction!
• If we study either, we try to fix everything
  else.
• Same breed
• Same of cows
• Same environment
• Same weigh day
• But outside of the lab, they arent fixed! So
  what do we do?

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Example

• Herd Health
• To study a disease, we isolate an animal from all
  other disease.
• But in a calving lot, a calf isnt isolated from
  cyrpto, e-coli, salmonella.
• Add in weather, time of year, slope.
• Add in colostrol immunity as affected by age of
  dam, breed makeup, nutrition.

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Characteristics of Complex Systems

• Tightly Coupled
• Dynamic
• Policy Resistant
• Counterintuitive
• Exhibit Tradeoffs

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4 Principles of Complex Systems

• Most problems are internally caused
• Obvious solutions are often the cause of problems
  or cause other problems
• Short term feedback tends to mislead people into
  taking ineffective or counterproductive action
• People cannot predict the results of their
  actions due to the complexity of problems

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Its a Process,not a Product!
Ranching

• Nels Smith
• Rancher, Wyoming

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Systems Dynamics

• Its a PROCESS!

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The Process of System Dynamics

• Identify the problem.
• Assemble collaborative team.
• Describe the problem.
• Search out the mental models.
• Use Causal Loop Diagrams to describe it.
• Use Computer models to add detail.
• Test.

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Identify the Problem

• Ranch profitability
• Fall out of young cows
• Matching cows to the environment
• Grazing systems
• Stocking rate
• Water quality

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Assemble a Collaborative Team

• NDSU SDSU
• Educators
• Specialists
• other Staff
• NRCS
• District Conservationists
• Range Conservationists
• Conservation Districts

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Describe the Problem
Weaning Weight
Ranch Profitability
Preg
Cull Sales
Breed
Calf Sales
Inventory Adj.
Land
Vet Cost
Equip
Feed Cost
Breeding Stock
Repair
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Mental Models

• Cows should calve in March and April!
• Calves born in May and June dont grow!
• Cows bred in the heat of August wont settle!
• Cows should be worm free but shouldnt calve in
  May?

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Causal Loop Diagrams
Limits To Success
Weather
Time of Calving
Live Calves
Death Loss
Nutrition
Repro
Calves Weaned/cow
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Computer Simulation

• PROSIM
• DECI
• BALANCER
• SUPPCOST

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Test

• Need data
• Need cooperators
• ?

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Range Management by Objective

• Stocking rate for livestock production?

• Stocking rate for grouse production?

• Stocking
• rate for
• prairie dog
• production?

A COMPLEX SITUATION WITH BOTH SHORT AND LONG TERM
CONSEQUENCES!