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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

FormationPolygonsArea (ha)Share of areaMean patch (ha)Median patch (ha)Largest patch (ha)Shape indexCentre (lat, lon)
Rhizophora dominant 10,36314,415.2
41.8%
1.390.091,277.4 1.38-2.113, 40.932
Rhizophora almost pure stand 2,0114,117.2
11.9%
2.050.18110.1 1.46-2.173, 40.848
Avicennia dominant 16,0713,968.9
11.5%
0.250.0953.3 1.29-2.106, 41.031
Mixture of Ceriops & Rhizophora 5,1833,833.9
11.1%
0.740.09164.2 1.38-2.009, 41.168
Ceriops dominant 11,0153,768.5
10.9%
0.340.09209.6 1.30-2.174, 40.943
Avicennia almost pure stand 13,4503,654.4
10.6%
0.270.09326.2 1.30-2.016, 41.047
Mixture of Rhizophora & Sonneratiaed 1,911755.8
2.2%
0.400.0946.9 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 inside
Field 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 formationMixture of Ceriops & R...Rhizophora dominantMixture of Rhizophora...(not on a mapped polyg...Rhizophora almost pure...Avicennia dominantCeriops dominantAvicennia almost pure...
Sonneratia rhizophora14221
Rhizophora almost pure stand11925
Rhizophora dominant161161
Sonneratia almost pure stand211911
Ceriops almost pure stand253
Avicennia dominant12551
Ceriops dominant11313
Mix ceriops rhizophora131121
—1
Avicennia almost pure stand1110221
Sand flat1
Sand flat clear sand area1

The 15 largest mangrove patches

#FormationArea (ha)Perimeter (m)Location
1Rhizophora dominant1,277.4117,588-2.1781, 40.9883 View on map →
2Rhizophora dominant738.698,824-1.7883, 41.4658 View on map →
3Rhizophora dominant623.554,625-2.0190, 41.1700 View on map →
4Rhizophora dominant328.540,023-2.1155, 41.1142 View on map →
5Avicennia almost pure stand326.272,492-1.8996, 41.0242 View on map →
6Rhizophora dominant295.439,503-1.9802, 41.2558 View on map →
7Rhizophora dominant281.226,349-2.1061, 41.1612 View on map →
8Rhizophora dominant257.026,011-2.1238, 41.1386 View on map →
9Avicennia almost pure stand238.047,969-1.9629, 40.8283 View on map →
10Ceriops dominant209.648,871-2.1606, 40.9828 View on map →
11Rhizophora dominant202.930,215-2.2305, 40.9557 View on map →
12Rhizophora dominant192.230,110-1.8960, 41.3679 View on map →
13Rhizophora dominant178.724,453-2.2916, 40.9519 View on map →
14Rhizophora dominant174.817,999-2.0202, 41.2052 View on map →
15Mixture of Ceriops & Rhizophora164.249,194-2.0957, 41.1101 View on map →
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