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Species & Formations
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Species & Formations
A closer look at the seven mangrove species formations mapped across the Lamu seascape (2019): how much of each there is, how it is patched together and how well the map agrees with what field teams found on the ground.
Formation classes
7
Distinct mapped classes
Mapped mangrove area
34,514 ha
60,004 polygons
Dominant by area
Rhizophora dominant
41.8% of mapped area
Evenness (Shannon, by area)
0.86
0 = one class dominates · 1 = perfectly even
How much of each formation?
Area is calculated from the stored geometry (hectares, WGS 84 ellipsoid)Mapped area by formation
Hectares
Source: WWF Kenya / KMFRI / KFS. Atlas recalculates every area from the geometry so all datasets share one unit.
Share of the number of polygons
How fragmented each formation is
Formation profile table
| Formation | Polygons | Area (ha) | Share of area | Mean patch (ha) | Median patch (ha) | Largest patch (ha) | Shape index | Centre (lat, lon) |
|---|---|---|---|---|---|---|---|---|
| Rhizophora dominant | 10,363 | 14,415.2 | 41.8% |
1.39 | 0.09 | 1,277.4 | 1.38 | -2.113, 40.932 |
| Rhizophora almost pure stand | 2,011 | 4,117.2 | 11.9% |
2.05 | 0.18 | 110.1 | 1.46 | -2.173, 40.848 |
| Avicennia dominant | 16,071 | 3,968.9 | 11.5% |
0.25 | 0.09 | 53.3 | 1.29 | -2.106, 41.031 |
| Mixture of Ceriops & Rhizophora | 5,183 | 3,833.9 | 11.1% |
0.74 | 0.09 | 164.2 | 1.38 | -2.009, 41.168 |
| Ceriops dominant | 11,015 | 3,768.5 | 10.9% |
0.34 | 0.09 | 209.6 | 1.30 | -2.174, 40.943 |
| Avicennia almost pure stand | 13,450 | 3,654.4 | 10.6% |
0.27 | 0.09 | 326.2 | 1.30 | -2.016, 41.047 |
| Mixture of Rhizophora & Sonneratiaed | 1,911 | 755.8 | 2.2% |
0.40 | 0.09 | 46.9 | 1.30 | -1.833, 41.424 |
Shape index = perimeter ÷ perimeter of a circle of the same area (1.0 = circle; higher = more irregular/elongated edge).
Patch structure
Mangrove stands are made of patches. Many small patches means a fragmented canopy.Polygons by size class
Count and area per size class
Fragmentation indicators
- Polygons
- 60,004
- Mean patch
- 0.58 ha · median 0.090 ha
- Largest patch
- 1,277.4 ha
- Tiny patches (< 0.1 ha)
- 37,924 (63.2% of polygons)
- Area in patches ≥ 10 ha
- 18,084 ha (52.4% of area)
- Area in the largest 100 patches
- 11,549 ha (33.5%)
How to read it: a long tail of tiny polygons next to a few very large ones is typical of satellite-derived classification of dense mangrove — it reflects mapping detail as much as real fragmentation.
North – south composition
Formation area in 0.1° latitude bands (about 11 km each)Does the map match the ground?
Field survey plots tested against the mapped polygon each one falls insideField plots tested
139
On a mapped polygon
103
36 outside the map
Dominant genus agrees (plots on the map)
52.4%
54 of 103 plots · at least one genus: 69%
Exact formation label agrees
19.4%
20 of 103 · field and map name classes differently
This is a simple consistency check, not a formal accuracy assessment: plot positions, formation names and dates may differ from the 2019 map.
Field formation (rows) vs mapped formation (columns)
| Field formation | Mixture of Ceriops & R... | Rhizophora dominant | Mixture of Rhizophora... | (not on a mapped polyg... | Rhizophora almost pure... | Avicennia dominant | Ceriops dominant | Avicennia almost pure... |
|---|---|---|---|---|---|---|---|---|
| Sonneratia rhizophora | 1 | 4 | 2 | 2 | 1 | |||
| Rhizophora almost pure stand | 1 | 19 | 2 | 5 | ||||
| Rhizophora dominant | 1 | 6 | 1 | 1 | 6 | 1 | ||
| Sonneratia almost pure stand | 2 | 1 | 1 | 9 | 1 | 1 | ||
| Ceriops almost pure stand | 2 | 5 | 3 | |||||
| Avicennia dominant | 1 | 2 | 5 | 5 | 1 | |||
| Ceriops dominant | 11 | 3 | 1 | 3 | ||||
| Mix ceriops rhizophora | 1 | 3 | 1 | 1 | 2 | 1 | ||
| — | 1 | |||||||
| Avicennia almost pure stand | 1 | 1 | 10 | 2 | 2 | 1 | ||
| Sand flat | 1 | |||||||
| Sand flat clear sand area | 1 |
The 15 largest mangrove patches
| # | Formation | Area (ha) | Perimeter (m) | Location | |
|---|---|---|---|---|---|
| 1 | Rhizophora dominant | 1,277.4 | 117,588 | -2.1781, 40.9883 | View on map → |
| 2 | Rhizophora dominant | 738.6 | 98,824 | -1.7883, 41.4658 | View on map → |
| 3 | Rhizophora dominant | 623.5 | 54,625 | -2.0190, 41.1700 | View on map → |
| 4 | Rhizophora dominant | 328.5 | 40,023 | -2.1155, 41.1142 | View on map → |
| 5 | Avicennia almost pure stand | 326.2 | 72,492 | -1.8996, 41.0242 | View on map → |
| 6 | Rhizophora dominant | 295.4 | 39,503 | -1.9802, 41.2558 | View on map → |
| 7 | Rhizophora dominant | 281.2 | 26,349 | -2.1061, 41.1612 | View on map → |
| 8 | Rhizophora dominant | 257.0 | 26,011 | -2.1238, 41.1386 | View on map → |
| 9 | Avicennia almost pure stand | 238.0 | 47,969 | -1.9629, 40.8283 | View on map → |
| 10 | Ceriops dominant | 209.6 | 48,871 | -2.1606, 40.9828 | View on map → |
| 11 | Rhizophora dominant | 202.9 | 30,215 | -2.2305, 40.9557 | View on map → |
| 12 | Rhizophora dominant | 192.2 | 30,110 | -1.8960, 41.3679 | View on map → |
| 13 | Rhizophora dominant | 178.7 | 24,453 | -2.2916, 40.9519 | View on map → |
| 14 | Rhizophora dominant | 174.8 | 17,999 | -2.0202, 41.2052 | View on map → |
| 15 | Mixture of Ceriops & Rhizophora | 164.2 | 49,194 | -2.0957, 41.1101 | View on map → |