Impact on biodiversity

The output of GLOBIO can basically be expressed in various biodiversity indicators. At the moment, the main indicators used are the Mean Species Abundance (MSA) and Ecosystem extent.

Mean Species Abundance

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

We emphasize that MSA does not completely cover the complex biodiversity concept. Complementary indicators should be included, when used in extensive biodiversity assessments. The GLOBIO team is currently 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.

Similar indicators

MSA can be considered a proxy for the CBD indicator on trends in species abundance. MSA is similar to the Biodiversity Integrity Index, the Biodiversity Intactness Index (BII) and the Living Planet Index (LPI).

The main difference between MSA and BII is that every hectare is given equal weight in MSA, whereas BII gives more weight to species rich areas.

The main difference with LPI is that MSA takes the pristine situation as a baseline, whereas LPI compares to the situation in 1970.

Ecosystem extent

Ecosystem extent is defined as the original area of a biome minus the area occupied by agricultural and urban land use. Ecosystem extent is calculated with models such as IMAGE at global level or CLUE at national or regional levels.