Mangrove biodiversity survey south of the Onilahy River - Frontier ...

Conclusions and recommendations
Mangrove trees are used for firewood and for making charcoal. In the East Africa region, many
mangrove forests (particularly those close to urban areas) have been subject to indiscriminate
cutting and the destruction of entire mangrove habitats (Semesi, 1996). Mangroves to the North of
Madagascar have been progressively exploited for firewood, with recent incursions into the
mangroves at Songoritelo being noted by Vasseur (1997), shrimp farming and salt extraction.
Although the pressure on the mangrove forests for charcoal remains small in this area due to the
local preference for xerophilic (terrestrial) timber (Lebigre, 1997), there is a local preference for A.
marina as a fuelwood (Frontier-Madagascar, unpublished data). Where mangroves are common
and close to centres of population (e.g. Toliara), they are subject to considerable felling activity. In
fact Salomon (1981) showed that the charcoal requirements of Toliara result in the clearance of
5,000ha of (terrestrial) forests annually; the natural xerophilic vegetation now covers only 27% of
the southwest of the country (Lebigre, 1997). As this terrestrial vegetation becomes exhausted, the
resources of the mangroves are more likely to come under threat.
Semesi and Howell (1989) state that the most destructive activities affecting mangroves are clearfelling
for rice cultivation, salt and charcoal production, aquaculture, or for firewood; whereas
selective felling for export and local construction purposes is not a major threat if adequately
controlled. Rice culture is not possible in this area (the driest in Madagascar), and can be
discounted as a threat to the mangroves. Traditional fishing in Western Madagascar relies
extensively on forest products, much of which originate from readily accessible mangroves
(Rasolofo, 1997), but there is little use of smaller mangroves for this purpose. Nor is salt
production a real concern for the tannes, since despite the favourable climate (Hamilton and
Snedacker, 1984), the dune-derived relief and access difficulties are probably enough of a logistical
barrier to discourage any large-scale operation. The major problems facing mangroves to the North
(poor agricultural practises, tree felling, salt production, and shrimp fishing and aquaculture (Iltis,
1997)) are largely absent from this section of the coastline, although the first two are present and are
likely to become increasingly important factors influencing the local environment.
The cutting of any mangrove tree technically requires a permit in Madagascar, but there is no
enforcement of this edict (Cooke et al., 2000). Mangrove wood is highly dense, an attribute that
confers resistance to fungi and termites (Semesi, 1996). For construction purposes the
Rhizophoraceae are most prized, as they most often have the forked trunk preferred for wooden
domiciles. Good management of mangrove forests has been demonstrated in Belo-sur-Mer, where
local people have exploited the resource in a sustainable manner for many decades (Henry Chartier
and Henry, 1997), and we conclude that the people living near these mangals are likewise already
engaged in an element of stewardship of their mangrove forest. With this in mind, a
recommendation can be made to the local village that the creek is dredged in order to link it with
the sea to prevent further mangal loss in Lovokampy.
The three mangals are far from a pristine condition and if they are to be conserved into the future
then management of their current diversity and restoration of a fuller diversity need to be the
priorities. These three mangals are all important sites for the proposed Man and Biosphere reserve
yet they are in a generally poor state of health being exploited by local populations and under threat
from environmental factors. Future work combining satellite imagery, GIS techniques,
hydrological, chemical and socio-economic studies, and continued biological survey work are
essential to production of a suitable management plan and monitoring scheme.
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