Modeling deforestation baselines using GEOMOD - Instituto ...

Finalizing Avoided Deforestation Baselines
Using IDRISI32 software, we created grids representing ‘distance from’ communities, rivers (perennial and
seasonal), roads, historical sites, 1970 agriculture, and water sources (perennial and seasonal). The final
set of candidate driver maps (Table 2) included seven ‘distance from’ maps, plus presence or absence of
wetlands (seasonal and perennial), density of persons involved in sector 1 economic activity (agriculture
and forestry), ejido boundaries and elevation (Table 2). Due to the high-resolution of the data employed for
this analysis and hence the large number of rows and columns, the computer memory to run the analysis
exceeded 1 Gb RAM. To realize our objective we split the region in half north and south. The northern half
consisted of 2605 rows by 3554 columns, the southern 2604 by 3554. Memory limitations also required use
of GEOMOD’s ‘non-neighborhood’ search option only. This greatly decreases model run time but sacrifices
some spatial accuracy. In order to preserve the rationale behind the neighborhood function we created a
“distance from prior disturbance” driver, in this case ‘distance from 1970s agriculture.’ If this factor is found
to be important then each cell could be weighted heuristically (see section III. B.) in order to force the model
to deforest in the neighborhood first. Similarly ‘distance from towns,’ if important, also gives greater weight
to forest lands lying proximate to ‘deforested’ population centers.
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