Land in IFs is divided into five categories—crop, grazing, forest, urban, and other land. Historical data on total land area (LDTot), crop land (LDl=1), grazing land (LDl=2), forest land (LDl=3), and other land (LDl=4) are taken from FAO data. Historical data on urban land (LDl=5) is taken from WRI. A few adjustments to the historical data are made in the pre-processor.
- Cropland is not allowed to exceed total crop production divided by 14, which places an effective limit on yield of 14 tons per hectare.
- Grazing land, forest land, and other land are bound from below to be at least 1000 hectares.
- If urban land is more than three quarters the area of other land, land is shifted from urban to other land
After these changes, total land area is recomputed as the sum of the area of the individual land categories.
The pre-processor also reads in a value for potentially arable land (landarablepot), which affects the amount of potential cropland in the model.
One final variable is estimated related to land in the pre-processor. This is the target rate of growth of cropland (tgrld). When data is available, this is currently estimated as the growth rate of cropland between the years 1992 and 2001.
When no data are available for cropland in either 1992 or 2001, the target rate of growth of cropland is estimated as a function of average income
with a maximum growth rate given as a function of cropland as a share of total land
Finally, this target growth rate is restricted to fall between -0.003 and +0.01.
In the first year, IFs estimates an initial unit cost of cropland development (CLD) as
IDS is the total investment in agriculture
IALK is the share of agricultural investment going to cropland development
dkl is a global parameter indicating the depreciation rate of investment in cropland, essentially a maintenance cost for existing cropland
tgrld is the target growth rate for cropland
A related factor (SCLDF), to be used in determining the cost of land development in future years, is also calculated in the first year
IFs calculates changes in land use for the coming year as a result of four key dynamic processes. First, changes in urban land may result from income and population changes. Second, economic shifts related to investment, particularly in the agricultural sector, can affect the amount of cropland. Third, IFs there can be expansion or retirement of grazing land for undefined reasons. Finally, in certain scenarios, specific changes in forest land can result from policies related to issues such as conservation and environmental protection.
For more, please click on the links below.
- Changes in Urban Land from Income and Population Changes
- Changes in Cropland due to Investment and/or Depreciation
- Changes in Grazing Land
- Change in Forest Land due to a Policy Choice
- Final Checks and Renormalization of Land Use