For each pressure X an MSA_{X} map is calculated by applying the causeâ€“effect relationship to the appropriate input map.

Assuming no interaction among the drivers, for each grid cell, GLOBIO calculates the overall MSA_{i} value by multiplying the MSA_{X} maps:

where i is a grid cell, MSA_{i} is the overall value for grid cell i, MSA_{Xi} 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).

Aggregation of results

To obtain the MSA_{r} of a region, GLOBIO calculates the area weighted mean of MSA_{i} values of all relevant grid cells (as grid cells have different areas).

where A_{i} is the land area of grid cell i.

Relative importance of drivers

The relative contribution of each driver to a loss in MSA may be calculated from formulas 1 and 2.