WOLFRAM SYSTEMMODELER

Land_Fertility

Land fertility

Diagram

Wolfram Language

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SystemModel["SystemDynamics.WorldDynamics.World3.Land_Fertility"]
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Information

This model computes the land fertility as a function of its utilization. Land can be overused. If that happens, the fertility of the land shrinks. This is likely to happen as the overall world population continues to climb.

The land fertility is measured in kilograms of equivalent vegetable food per hectare and year. Arable land can be used to either grow vegetable food directly, or alternatively, to raise animals that then enter the human food chain. Yet it takes more land per human to raise animals than to grow vegetable food. For this reason, it is meaningful to convert proteins obtained from eating meat to equivalent units of vegetable food.

Notice that this model uses two different types of rate models. Whereas the yield technology rate is a so-called bi-flow, i.e., it can assume both positive and negative values leading to a change of flow direction, the land fertility integrator uses uni-flows, i.e., flows that are allowed to flow in the indicated direction only.

Public Parameters (6)

des_food_ratio_dfr

Value: 2

Type: Real

Description: Desired food ratio

inherent_land_fert

Value: 600

Type: Real (kg/(hectare·yr))

Description: Inherent land fertility

land_fertility_init

Value: 600

Type: Real (kg/(hectare·yr))

Description: Initial industrial investment

t_policy_year

Value: 4000

Type: Real (yr)

Description: Year of policy change

yield_tech_init

Value: 1

Type: Real

Description: Initial yield technology factor

p_yield_tech_chg_mlt

Value: {0, 0, 0, 0}

Type: Real[:]

Description: Yield technology change multiplier

Connectors (5)

p_fr_inp_for_land_maint

Type: MassInPort

Description: Fraction of investments in the agricultural sector allocated to land maintenance

ppoll_index

Type: MassInPort

Description: Persistent pollution index

land_fertility

Type: MassOutPort

Description: Land fertility

food_ratio

Type: MassInPort

Description: Food ratio

yield_tech_LYTD

Type: MassOutPort

Description: Technology induced absolute yield enhancement

Components (16)

Source1

Type: Source

Land_Fert_Regen

Type: RRate

Description: p.328 of Dynamics of Growth in a Finite World

Land_Fertility

Type: Level

Description: p.324 of Dynamics of Growth in a Finite World

Land_Fert_Degr

Type: RRate

Description: p.326 of Dynamics of Growth in a Finite World

Sink1

Type: Sink

Land_Fert_Reg

Type: Land_Fert_Reg

Description: p.328 of Dynamics of Growth in a Finite World

Land_Fert_Deg

Type: Prod_2

Description: p.326 of Dynamics of Growth in a Finite World

Land_Fert_Regen_Time

Type: Tabular

Description: p.330 of Dynamics of Growth in a Finite World

Land_Fert_Degr_Rt

Type: Tabular

Description: p.326 of Dynamics of Growth in a Finite World

Yield_Tech_Chg_Rt_LYTDR

Type: Rate_1

Yield_Tech_Chg_Rt

Type: Yield_Tech_Chg_Rt

P_Yield_Tech_Chg_Mlt_LYCM

Type: Tabular

Add1

Type: Add

Des_Food_Ratio_DFR

Type: Const

Source2

Type: Source

Yield_Tech_LYTD

Type: Level1a

Used in Examples (11)

Scenario_11

SystemDynamics.WorldDynamics.World3

Influencing the future 10 years later

Scenario_10

SystemDynamics.WorldDynamics.World3

Influencing the future 20 years earlier

Scenario_9

SystemDynamics.WorldDynamics.World3

Combining the measures of Scenarios #6 and #8

Scenario_8

SystemDynamics.WorldDynamics.World3

More abundant non-recoverable natural resources, birth control, and stable industrial output

Scenario_7

SystemDynamics.WorldDynamics.World3

More abundant non-recoverable natural resources and birth control

Scenario_6

SystemDynamics.WorldDynamics.World3

More accessible non-recoverable natural resources, pollution control, land yield enhancement, erosion protection, and resource efficiency

Scenario_5

SystemDynamics.WorldDynamics.World3

More accessible non-recoverable natural resources, pollution control, land yield enhancement, and erosion protection

Scenario_4

SystemDynamics.WorldDynamics.World3

More accessible non-recoverable natural resources, pollution control, and land yield enhancement

Scenario_3

SystemDynamics.WorldDynamics.World3

More accessible non-recoverable natural resources and pollution control

Scenario_2

SystemDynamics.WorldDynamics.World3

More abundant non-recoverable natural resources

Scenario_1

SystemDynamics.WorldDynamics.World3

Original WORLD3 model