Impact on biodiversity

The output of GLOBIO-Aquatic can basically be expressed in various biodiversity indicators. At the moment, the main indicators used is the Mean Species Abundance (MSA).

MSA is an indicator of naturalness or biodiversity intactness. It is defined as the mean abundance of original species relative to their abundance in undisturbed ecosystems. An area with an MSA of 100% means a biodiversity that is similar to the natural situation. An MSA of 0% means a completely destructed ecosystem, with no original species remaining.

MSA gradient for forest and grassland, illustrated with images
MSA gradient for forest and grassland, illustrated with images

The MSA index is comparable to the Biodiversity Intactness Index (BII). It is also closely related to and correlated with the Index of Biotic Integrity (IBI) that is widely used in the aquatic realm.

We emphasize that MSA does not completely cover the complex biodiversity concept. Complementary indicators should be included, when used in biodiversity assessments. The GLOBIO team is exploring options to model additional indicators.


The MSA is calculated by:

  1. Calculation of MSA per driver, using the cause-effect relationships, per grid cell of the map
  2. Combining the MSA value of all drivers to a total MSA per grid cell
  3. Aggregation across grid cells, e.g. towards global or regional MSA values

The output resolution depends on the input maps. For global analyses the resolution is 0.5 by 0.5 degree (nearly 55*55 km near the equator). For national analyses often 1 by 1 km is used.

Other indicators

Besides the biodiversity intactness, also the species richness is calculated as output. An additional output for lakes is the probability of occurrence of harmful algal blooms.