Land Allocation

Land-Cover Model, model structure

Model steps

Five steps can be distinguished within the model:

1) Adaptating of natural vegetation 

• Potential migration zones are calculated using maximum dispersal distances and migration rates
• Potential and natural vegetation are compared at the grid-cell level
• If differences are encountered: 
  - the ability of those cells to adapt is assessed (i.e., for adaptation cells must be within the potential migration zone) 
  - cells that are able to adapt will convert from the original to a new vegetation type using assumptions for transition periods.                         

2) Treating unsuitable land and extensive grassland

• Extensive grassland is defined as land with 'grass and fodder species' with potential productivity less than 25% of the theoretical maximum potential
• Extensive grasslands are fixed over time
• Agricultural land, not being extensive grassland, is considered unsuitable or too marginal for agriculture if potential productivity drops below 10% of the theoretical maximum potential
• Unsuitable land reverts back to its natural vegetation.                         

3) Extracting timber

• Agricultural land, regrowth forest and protected reserves are excluded
• Preferences of grid cells for timber extraction are based on: 
  - minimal distance to agricultural land, regrowth forest, and large rivers and other bodies of water
  - forest coverage within a cell
  - random preference     
• Timber is extracted from cells with the highest preference values until regional timber demand is satisfied
• Vegetation regrows to its original state after exploitation, unless it is converted into agricultural land.                         

4) Abandoning and reallocating existing agricultural land

• Agricultural grid cells are sorted according to their crop productivity
• The grid cell having the highest crop productivity from the previous time step a certain amount of the area within each cell is allocated to a particular crop on the basis of the 'local' potential productivity for that crop, as well as changes in regional demand
• Agricultural land that is not allocated is taken out of production. This land is either not needed to meet crop demands or has become unsuitable to meet these demands
• After being abandoned land, reverts back to its natural vegetation.                         

5) Expanding agricultural land

• Agricultural land and protected bioreserves are excluded
• Preferences of grid cells for expansion of agricultural land are based on: 
  - minimal distance to agricultural land and large rivers and other bodies of water
  - potential productivity of crops
  - population density
  - random preference     
• Expansion of agricultural land starts with grid cells with highest preference values until regional crop demands are satisfied or until all suitable land is used
• Crops are allocated over these cells using potential productivity and remaining crops demand.
  

For a full description of the land-cover model, see Alcamo et al. (1998).                   

• to  Livestock Production Systems
• to  external references
• to  MNP references