blockLand_Fertility

Land fertility
Diagram of Land_Fertility

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.

Parameters

TypeNameDefaultDescription
Realdes_food_ratio_dfr2Desired food ratio
Realinherent_land_fert600Inherent land fertility
Realland_fertility_init600Initial industrial investment
Realt_policy_year4000Year of policy change
Realyield_tech_init1Initial yield technology factor
Real[:]p_yield_tech_chg_mlt{0, 0, 0, 0}Yield technology change multiplier

Connectors

TypeNameDefaultDescription
SystemDynamics.Interfaces.MassInPortp_fr_inp_for_land_maintFraction of investments in the agricultural sector allocated to land maintenance
SystemDynamics.Interfaces.MassInPortppoll_indexPersistent pollution index
SystemDynamics.Interfaces.MassOutPortland_fertilityLand fertility
SystemDynamics.Interfaces.MassInPortfood_ratioFood ratio
SystemDynamics.Interfaces.MassOutPortyield_tech_LYTDTechnology induced absolute yield enhancement

Components

TypeNameDefaultDescription
SystemDynamics.Sources.SourceSource1
SystemDynamics.Rates.RRateLand_Fert_Regenp.328 of Dynamics of Growth in a Finite World
SystemDynamics.Levels.LevelLand_Fertilityp.324 of Dynamics of Growth in a Finite World
SystemDynamics.Rates.RRateLand_Fert_Degrp.326 of Dynamics of Growth in a Finite World
SystemDynamics.Sources.SinkSink1
SystemDynamics.WorldDynamics.World3.Utilities.Land_Fert_RegLand_Fert_Regp.328 of Dynamics of Growth in a Finite World
SystemDynamics.Auxiliary.Prod_2Land_Fert_Degp.326 of Dynamics of Growth in a Finite World
SystemDynamics.Functions.TabularLand_Fert_Regen_Timep.330 of Dynamics of Growth in a Finite World
SystemDynamics.Functions.TabularLand_Fert_Degr_Rtp.326 of Dynamics of Growth in a Finite World
SystemDynamics.Rates.Rate_1Yield_Tech_Chg_Rt_LYTDR
SystemDynamics.WorldDynamics.World3.Utilities.Yield_Tech_Chg_RtYield_Tech_Chg_Rt
SystemDynamics.Functions.TabularP_Yield_Tech_Chg_Mlt_LYCM
Modelica.Blocks.Math.AddAdd1
SystemDynamics.Auxiliary.ConstDes_Food_Ratio_DFR
SystemDynamics.Sources.SourceSource2
SystemDynamics.Levels.Level1aYield_Tech_LYTD