Atlas · Mali
/
Methodologies
METHODOLOGIES
Fragmentation metrics
Effective mesh size, largest patch index and patch-size power law.
Method
Effective mesh size (Jaeger 2000): m = Σ aᵢ² / A, the area of the patch you would land in if you dropped a random point on mangrove. Largest patch index = largest patch ÷ total area × 100.
Power-law exponent α uses the maximum-likelihood estimator of Clauset, Shalizi & Newman (2009) for patches above a minimum size x_min.
How to interpret it
A bigger effective mesh size means a less fragmented landscape. A heavy-tailed size distribution (small α) means a few very large stands carry most of the area.
Limits. Patches cut by the mapping boundary are counted as separate patches.
Related reading
More in Methodologies
- Diversity: Shannon index and evenness
- Spatial statistics: Moran's I and Getis-Ord Gi*
- How recommendations and briefs are generated
- The official yearly series (1985–2025)
- Why Atlas totals are 2.3% higher than the official figures
- How Global Mangrove Watch maps are made
- Field plots versus the map
- Geodesic area and perimeter
Still have a question?
The AI analyst answers from these articles and from the data.
Ask Atlas