West African Coastal Area: Challenges and Outlook - The Land/Ocean Interactions in the Coastal Zone of West and Central Africa - page 16

Fig. 4 Proportion of coastline
according to physiography of
mangrove stands (the whole of
the study area) (SDLAO)

harrisonnii, R. racemosa, Avicennia germinans, and Lag-
uncularia racemosa, Acrostichum aureum, Conocarpus
erectus) are also distributed on the eastern coasts of tropical
America. These mangroves grow in the intertidal zone.
They cover approximately 14,000 km 2 in the zone under
study and are subject to the influence of various factors:
oceanographic, sedimentary, geomorphologic, but also and
increasingly, anthropic.
Not very diversified from a floristic point of view, these
mangrove communities nonetheless play a vital role for the
coastal ecosystems as a whole, in particular by the high net
production that characterises them, which is exported to
marine milieus and enables a rich and diverse piscifauna to
be maintained. Their physiographic characteristics (shallow
gradients, the cryptic nature of milieus that are crowded
with the roots of the mangrove trees) also make them
essential reproduction zones for a high proportion of fish
species that make up the region's fishing stocks. The small
areas of estuarine mangroves in the Gulf of Guinea, par-
ticularly in countries like Togo and Benin, are extremely
threatened and specific protection measures are required.
The pressure on the mangroves and on these coastal eco-
systems is increasing today. A distinction should be made
between:
• Biomass removal: wood for energy (supplying the nearby
urban concentrations for smoking fish or producing salt in
Guinea), for services, fisheries and the gathering of
attached organisms, molluscs and crustaceans, removal of
bark and of various species in traditional pharmacopeia.
• Conversions and clearance: artificialisation for rice pro-
duction, salt production, or shrimp farming, which is
expected to expand in the future, in particular in Guinea.
The surface area occupied by mangroves in the region is
thought to have decreased by a quarter between 1980 and
2006 (Corcoran 2009 )
The changes in the surface areas of mangroves (con-
traction

continental drought cycles or, on the contrary, abundant
rainfall. These systems are particularly dynamic and sen-
sitive to changes in mud banks, the physiognomy and
topography of which are under the influence of coastal
hydro-sediment forcing.
Preserving these original systems also conditions that of
the veritable ethno-ecosystem that characterise these areas
and their population which was largely dependent on a daily
basis on resources valorised locally through complex pro-
duction systems adapted to these particular milieus. The
contribution of these ecosystems to the subsistence strate-
gies of certain coastal societies (in Sine Saloum, Casa-
mance, the Gambia, Guinea Bissau, Guinea and Sierra
Leone) is fundamental, as much at the level of food, food
security and pharmacopeia as from a cultural point of view
(Figs. 4 and 5 ).

Five West African governments (Mauritania, the
Gambia, Guinea, Guinea Bissau and Serra Leone)
have ratified a charter that commits them to cooperate
for the protection of the mangrove in the sub-region.
This mangrove protection charter also comprises
detailed plans of action specific to each country.

Estuaries

Estuaries constitute areas of particular importance for the
interpenetration of marine and fluvial environments,
favouring different ecological processes and the exchange
of nutrients, which, depending on the season, are used by a
wide variety of fishes and crustaceans species, some at
specific stages in their life cycle. The estuaries of West
Africa are home to the major expanses of mangroves, which
are reputed for their biological productiveness and their role

or expansion) are, however, also governed by