For each pressure X an MSAX map is calculated by applying the cause–effect relationship to the appropriate input map.
Assuming no interaction among the drivers, for each grid cell, GLOBIO calculates the overall MSAi value by multiplying the MSAX maps:
where i is a grid cell, MSAi is the overall value for grid cell i, MSAXi is the relative mean species abundance corresponding to the drivers LU (land use), N (atmospheric nitrogen deposition), I (infrastructure), F (fragmentation), and CC (climate change).
To obtain the MSAr of a region, GLOBIO calculates the area weighted mean of MSAi values of all relevant grid cells (as grid cells have different areas).
where Ai is the land area of grid cell i.
The relative contribution of each driver to a loss in MSA may be calculated from formulas 1 and 2.