MSA (Mean Species Abundance) is a composite indicator of biodiversity intactness, defined as the mean abundance of original species relative to their abundance in undisturbed reference ecosystems. An MSA value of 1 corresponds to a pristine ecosystem (full intactness); an MSA value of 0 indicates the complete loss of original species.
MSA is articulated into distinct components measuring the impact of specific biodiversity loss drivers:
The overall MSA value is the area-weighted mean of the CLC (Corine Land Cover) classes present in the site.
MSA is calculated using the GLOBIO methodology (Global Biodiversity Model for Policy Support), developed by PBL Netherlands Environmental Assessment Agency (Alkemade et al., 2009; Schipper et al., 2020).
Calculation steps:
Current version: v2 (evolution from v0 → v1 → v2)
| Code | Name | Provider | Resolution | Availability |
|---|---|---|---|---|
WRD_GLOBX_99 | GLOBIO MSA Model | PBL Netherlands Environmental Assessment Agency | variable | on request |
WRD_CRNLC_99 | Corine Land Cover | EEA | 100 m | 1990 — 2018 |
WRD_CLCBB_99 | CLC Backbone | EEA | 100 m | 2012, 2018 |
| Indicator | Unit | Range | Inverted |
|---|---|---|---|
msa | — | [0, 30, 50, 65, 80, 100] | No |
msa_cc | — | [75, 80, 85, 90, 95, 100] | No |
msa_i | — | [66, 73, 80, 87, 94, 100] | No |
msa_f | — | [80, 84, 88, 92, 96, 100] | No |
msa_lu_plants | — | no range defined | No |
msa_lu_animals | — | no range defined | No |
msa_ha | ha | [0, 5, 10, 20, 50, 100] | Yes |
Note: msa_ha is inverted (Yes): a higher number of degraded hectares indicates a worse situation.
Quality levels for MSA (main indicator):
| Level | MSA (%) | Interpretation |
|---|---|---|
| A (Excellent) | 80 – 100 | Near-undisturbed ecosystem; high biodiversity intactness |
| B (Good) | 65 – 80 | Good intactness; original species dominant |
| C (Moderate) | 50 – 65 | Moderate intactness; measurable but non-critical anthropic impact |
| D (Poor) | 30 – 50 | Low intactness; significant reduction of original species |
| E (Critical) | 0 – 30 | Severe degradation; ecosystem strongly altered from pristine state |
Responsible: Claudio Barbieri (MSA_LU and MSA_CC), Axel Dolcemascolo (MSA_I and MSA_F)
msa
msa_cc
msa_i
msa_f
msa_lu_plants
msa_lu_animals
msa_ha
Calculated using the GLOBIO methodology (Global Biodiversity Model for Policy Support, PBL Netherlands, WRD_GLOBX_99). The CLC land cover is classified and each class is assigned MSA_LU values (with fauna and flora sub-components) from GLOBIO look-up tables calibrated through ecological meta-analysis. MSA_CC estimates climate change impact (range 0.75–1), MSA_I infrastructure effects as a function of distance (range 0.67–1), MSA_F habitat fragmentation (range 0.80–1). The final value is the area-weighted mean of CLC classes within the polygon. MSA_HA converts degradation into equivalent lost hectares (inverted indicator). Current version: v2.