WOLFRAM SYSTEM MODELER
Food_ProductionFood production |
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Diagram
Wolfram Language
In[1]:=
SystemModel["SystemDynamics.WorldDynamics.World3.Food_Production"]
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Information
This model describes the production of food. Food is a controlled variable, as farmers decide what to grow and how much to grow on the basis of their perception of what they can sell. Consequently, the model uses the perceived food ratio as a state variable. If the farmers decide that too much food is being produced already, they'll produce less next year, and vice versa.
A second state variable describes the capital that is being invested in growing food. Since that capital (for example, the capital expended in buying food harvesting machines) cannot be allocated or freed instantaneously, it makes sense to maintain also that variable as a state variable.
The agricultural input is measured in dollars/year, whereas the food ratio is dimensionless.
Parameters (11)
| agr_inp_init |
Value: 5000000000.0 Type: Real (dollar/yr) Description: Initial agricultural input |
|---|---|
| food_short_perc_del |
Value: 2 Type: Real (yr) Description: Food shortage perception delay |
| land_fr_harvested |
Value: 0.7 Type: Real Description: Land fraction harvested |
| p_avg_life_agr_inp_1 |
Value: 2 Type: Real (yr) Description: Default average life of agricultural input |
| p_avg_life_agr_inp_2 |
Value: 2 Type: Real (yr) Description: Controlled average life of agricultural input |
| p_land_yield_fact_1 |
Value: 1 Type: Real Description: Default land yield factor |
| perc_food_ratio_init |
Value: 1 Type: Real Description: Initial perceived food ratio |
| processing_loss |
Value: 0.1 Type: Real Description: Processing loss |
| subsist_food_pc |
Value: 230 Type: Real (kg/yr) Description: Available per capita food |
| t_policy_year |
Value: 4000 Type: Real (yr) Description: Year of policy change |
| tech_dev_del_TDD |
Value: 20 Type: Real (yr) Description: Technology development time |
Connectors (17)
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ind_out_pc |
Type: MassInPort Description: Per capita annual industrial output |
|---|---|---|
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industrial_output |
Type: MassInPort Description: Annual industrial output |
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fr_inp_al_land_dev |
Type: MassInPort Description: Fraction of capital invested in agriculture allocated to the devlopment of arable land |
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arable_land |
Type: MassInPort Description: Arable land |
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marg_prod_agr_inp |
Type: MassOutPort Description: Development of marginally producing land |
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land_yield |
Type: MassOutPort Description: Land yield |
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population |
Type: MassInPort Description: Population |
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yield_tech_LYTD |
Type: MassInPort Description: Technology induced absolute yield enhancement |
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land_fertility |
Type: MassInPort Description: Land fertility |
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s_yield_mlt_air_poll |
Type: MassInPort Description: Land yield multiplier from air pollution |
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food_ratio |
Type: MassOutPort Description: Food ratio |
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tot_agric_invest |
Type: MassOutPort Description: Total investment in the agricultural sector |
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agr_inp_per_hect |
Type: MassOutPort Description: Agricultural investments per hectare |
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s_fioa_agr |
Type: MassOutPort Description: Fraction of total investments allocated to the agricultural sector |
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p_fr_inp_for_land_maint |
Type: MassOutPort Description: Fraction of investments in the agricultural sector allocated to land maintenance |
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yield_tech_mult_icor_COYM |
Type: MassOutPort Description: Technology induced relative enhancement of land yield |
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food_pc |
Type: MassOutPort Description: Per capita annually consumed food |
Components (30)
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P_Indic_Food_PC_1 |
Type: Tabular Description: p.286 of Dynamics of Growth in a Finite World |
|---|---|---|
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P_Indic_Food_PC_2 |
Type: Tabular Description: p.286 of Dynamics of Growth in a Finite World |
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S_Indic_Food_PC |
Type: S_Indic_Food_PC Description: p.286 of Dynamics of Growth in a Finite World |
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P_Fr_IO_Al_Agr_1 |
Type: Tabular Description: p.287 of Dynamics of Growth in a Finite World |
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Div1 |
Type: Division Description: Output first input divided by second input |
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P_Fr_IO_Al_Agr_2 |
Type: Tabular Description: p.287 of Dynamics of Growth in a Finite World |
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S_FIOA_Agr |
Type: S_FIOA_Agr Description: p.287 of Dynamics of Growth in a Finite World |
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Tot_Agric_Invest |
Type: Prod_2 Description: p.287 of Dynamics of Growth in a Finite World |
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Source1 |
Type: Source Description: This is the (dummy) source model of System Dynamics |
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Chg_Agr_Inp |
Type: Rate_1 Description: Unrestricted rate element with one influencing variable |
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Agr_Inp |
Type: Level1a Description: General System Dynamics level with no outflow |
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Ch_Agr_Inp |
Type: Ch_Agr_Inp Description: p.292 of Dynamics of Growth in a Finite World |
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Current_Agr_Inp |
Type: Current_Agr_Inp Description: p.292 of Dynamics of Growth in a Finite World |
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S_Avg_Life_Agr_Inp |
Type: S_Avg_Life_Agr_Inp Description: p.293 of Dynamics of Growth in a Finite World |
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P_Fr_Inp_For_Land_Maint |
Type: Tabular Description: p.332 of Dynamics of Growth in a Finite World |
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Source2 |
Type: Source Description: This is the (dummy) source model of System Dynamics |
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Chg_Perc_Food_Ratio |
Type: Rate_1 Description: Unrestricted rate element with one influencing variable |
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Perc_Food_Ratio |
Type: Level1a Description: General System Dynamics level with no outflow |
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Agr_Inp_Per_Hect |
Type: Agr_Inp_Per_Hect Description: p.294 of Dynamics of Growth in a Finite World |
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Marg_Land_Yield_Mlt_Cap |
Type: Tabular Description: p.313 of Dynamics of Growth in a Finite World |
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Land_Yield_Mlt_Cap |
Type: Tabular Description: p.306 of Dynamics of Growth in a Finite World |
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Land_Yield |
Type: Prod_4 Description: p.307 of Dynamics of Growth in a Finite World |
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Marg_Prod_Agr_Inp |
Type: Marg_Prod_Agr_Inp Description: p.313 of Dynamics of Growth in a Finite World |
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Food |
Type: Food Description: p.280 of Dynamics of Growth in a Finite World |
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Food_PC |
Type: Division Description: p.281 of Dynamics of Growth in a Finite World |
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Food_Ratio |
Type: Gain Description: p.332 of Dynamics of Growth in a Finite World |
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Ch_Perc_Food_Ratio |
Type: Ch_Perc_Food_Ratio Description: p.333 of Dynamics of Growth in a Finite World |
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S_Land_Yield_Fact |
Type: S_Land_Yield_Fact Description: p.307 of Dynamics of Growth in a Finite World |
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P_Land_Yield_Fact_2 |
Type: SMTH3 Description: Third-order exponential smoothing |
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Yield_Tech_Mult_Icor_COYM |
Type: Tabular Description: Tabular function |
Used in Examples (11)
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SystemDynamics.WorldDynamics.World3 Original WORLD3 model |
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SystemDynamics.WorldDynamics.World3 More abundant non-recoverable natural resources |
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SystemDynamics.WorldDynamics.World3 More accessible non-recoverable natural resources and pollution control |
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SystemDynamics.WorldDynamics.World3 More accessible non-recoverable natural resources, pollution control, and land yield enhancement |
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SystemDynamics.WorldDynamics.World3 More accessible non-recoverable natural resources, pollution control, land yield enhancement, and erosion protection |
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SystemDynamics.WorldDynamics.World3 More accessible non-recoverable natural resources, pollution control, land yield enhancement, erosion protection, and resource efficiency |
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SystemDynamics.WorldDynamics.World3 More abundant non-recoverable natural resources and birth control |
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SystemDynamics.WorldDynamics.World3 More abundant non-recoverable natural resources, birth control, and stable industrial output |
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SystemDynamics.WorldDynamics.World3 Combining the measures of Scenarios #6 and #8 |
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SystemDynamics.WorldDynamics.World3 Influencing the future 20 years earlier |
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SystemDynamics.WorldDynamics.World3 Influencing the future 10 years later |