GLOBIO calculates the effects of atmospheric nitrogen deposition using the nitrogen (N) deposition in excess of critical loads (N exceedance). For separate biomes (log) linear regression models describe the relationship between N exceedance and MSA.
The cause-effect relationships are based on 22 studies on the experimental addition of nitrogen to natural systems and its effects on species richness and species diversity. To build the regression equations, the relative local species richness is used as a proxy for MSA.
For croplands, GLOBIO considers atmospheric N deposition not to affect MSA, because the atmospheric N deposition is relatively small compared to the addition of N by fertilizers. The latter is already accounted for in the estimation of agricultural impacts (land use).