Description
Mean Species Abundance (MSA) is an estimate of the mean abundance of original species relative to their abundance in undisturbed ecosystems. The MSA is generally an indicator for biodiversity as it measures the abundance of original species in relation to the ecosystems in which they exist. A score of 0 means that the area is projected to be completely destroyed. A score of 1 means that the area is projected to be largely intact. The layers are the future projected layers for Mean Species Abundance in 2050 under three SSP scenarios - SSP1-2.6, SSP3-6.0 and SSP5-8.5. These layers contain the area-weighted mean MSA for watershed regions at different HydroBASINS levels.
Technical Description
The Mean Species Abundance (MSA) metric serves as an indicator of the intactness of local biodiversity. MSA values range from 0 to 1, with 1 indicating a completely intact species assemblage, and 0 indicating the local extinction of all original species. MSA is determined by comparing the current abundance of individual species under certain pressures to their abundance in an undisturbed or natural reference state. The calculation includes only those species that are present in the undisturbed state, and disregards any increase in species abundance from the reference to the impacted state. This approach prevents the indicator from being skewed by species that thrive in disturbed habitats. The MSA data is produced using the GLOBIO model by Schipper et al., 2020 which assesses local terrestrial biodiversity intactness using the mean species abundance (MSA) indicator, which is influenced by six human pressures: land use, road disturbance, fragmentation, hunting, atmospheric nitrogen deposition, and climate change. At the heart of the model are established quantitative relationships between these pressures and their impacts, derived from comprehensive terrestrial biodiversity databases.
The study evaluated the changes in terrestrial biodiversity intactness, as indicated by the mean species abundance (MSA) metric, across three shared socio-economic pathways (SSPs) combined with varying levels of climate change based on representative concentration pathways (Schipper et al., 2020). Projections for SSP1-2.6, SSP3-6.0 and SSP5-8.5 out to 2050 were generated, representing the effects of land use and climate changes associated with the selected scenarios.
This Collection holds the area-weighted mean projected MSA for watershed regions at different HydroSHEDS HydroBASINS sub-basin watershed levels. Lake watersheds are removed prior to calculation of the weighted averages.