Demand

The DEMAND module of FUTURES determines the quantity of land change expected. This is specified by the user in the demand table as the number of cells to be converted at each time step for each sub-region.

###Preparation of the demand table for Status Quo conditions

Data required

1. area developed over time
2. observed population over time
3. population projections for the years to be simulated

Step 1. Quantify the amount of development that has occurred for each region at each of a selection of historical time steps (for example, the amount of development in each county in 1970, 1980, 1990, and 2000). Data are most often obtained via a remotely sensed land cover product.

Step 2. Determine the population of each region for each of those selected time steps. Data are often obtained from state records.

Step 3. Perform ordinary least squares regression where the amount of development is determined as a function of the population present. Note that depending on the study area, alternative relationships may be more appropriate than a linear trend, a logarithmic relationship for example.

Step 4. Determine the amount of land that will need to be developed to accommodate future populations. This is done by solving the regression equation for each year to be simulated.

Step 5. Calculate the number of grid cells that need to be converted at each time step (equivalent to the amount of land determined above).

Preparation of the demand table for scenario analysis

Modify the table for different demand scenarios – replace the status quo demand table with the table containing the development amount of interest.