Mangrove forests in a peri-urban setting: the case of Mombasa (Kenya)

The structure and regeneration patterns of
the peri-urban mangrove vegetation of Mombasa at
Tudor creek were studied along belt transects at two
forest sites of Kombeni and Tsalu. Based on the
species importance values, the dominant mangrove
species were Rhizophora mucronata Lam. (Rhizophoraceae)
and Avicennia marina (Forssk.) Vierh.
(Avicenniaceae). Lumnitzera racemosa Willd.,
reported in an earlier floristic survey, was not
encountered. Tree density varied from 1,264 trees
ha-1 at Kombeni to 1,301 trees ha-1 at Tsalu and
mean tree height was higher at the former site
compared to the latter. The size-class structure at both localities showed the numerical dominance of small
trees over larger trees. The spatial distribution pattern
of adults and juveniles varied greatly between sites
and showed a close to uniform pattern (Morisita's
Index Id 1) for adult trees, but a tendency to
clustered distribution (Id 1) for juveniles. The
present paper shows that unmanaged but exploited
peri-urban mangroves are structurally stressed, having
enlarged canopy gaps that are characterised by
spatial and temporal site heterogeneity that influences
regeneration, implying longer periods for canopy
closure. Diversifying uses of mangrove products and
establishing reserves as no cut zones with regulated
harvesting will minimise canopy gap sizes, and
promote conservation practices. The proposed management
strategy shall boost the ecosystem resilience
to both anthropogenic and natural stressors expected
in the peri-urban setting in the long run.