111
Douala has a coastal nature, with the presence of water and mangroves, especially the river Wouri estuary. It is common to find dwellings surrounded by scanty
or permanent water. Much of the city is less planned and is not built sustainably: less
than 8% of the total area is occupied by condominium, multi-storey, villa and single
storey, whereas mixed construction has a surface area of 23.5% and mud/wood
construction, 20.4% (CLUVA 2010). This indicates a very poor population and
hence a high pressure on natural resources and vegetation. Plantations, parks, and
agriculture cover only a little part of the area. In the face of the rapid urban expansion for the past 20 years, it is certain that the demand for sand, soils and scoria
would remain elastic. The profitability and others facilities offered by the Douala
city favored this activity and induced the increment of quarries.
Urbanization is one of the most unfavorable factors to the conservation and evolution of terrestrial ecosystems in emerging or developing countries (Fig. 3.12). The
Cameroon coast contains four major cities with mangrove stands border agglomerations from Kribi to Limbe. Mangroves of Kribi were heavily damaged by the installation of modern buildings at the seaside (Nfotabong-Atheull 2011). The construction
of tourist complexes after the realization of the asphalt road that connects Kribi to
Edea have spared no specimen of mangroves (Din 2001). The development of the
city of Tiko destroyed mangrove mainly in the old port that was certainly attracted
people in the area. The installation of new populations favored the destruction of a
major band of mangrove.
The establishment of roads inside mangroves led to an ecological fragmentation
and isolation of two sides of mangroves that can no more exchange materials
between them. The general aspect of the vegetation (composition and structure) corresponds to a senescent stand where swamp forest species gradually invade the site.
Mangrove ecosystems could survive after fragmentation if the derivative forests are
regularly watered by daily tides. The zonation and the progressive series change and
affect deeply the structure of the forest but the composition will remain unchanged
even if the structure of trees is also affected. Species like Nypa fruticans take advantage of such phenomenon to occupy more space.
Although mangroves contribute considerably to the social and economic wellbeing of the Cameroon coastal inhabitants, their total surface area has decreased by
30% in 20 years (Spalding et al. 2010), mainly due to rapid and uncontrolled urbanization around Douala city (Din et al. 2002; Ellison and Zouh 2012; NfotabongAtheull et al. 2013).
3.4.5 Wastes
Wastes and wastewater discharged into nearby mangrove forest, marshes and rivers
can finally get into the mangroves ecosystem due to rainfalls, currents and tide
movements. Direct discharges into mangroves are frequently observed in the Wouri
estuarine mangrove. The mangrove areas are daily transformed as solid and liquid
waste disposals accepted by the Douala urban council without any restriction
3 Impact of Urbanization on the Evolution of Mangrove Ecosystems…
Douala has a coastal nature, with the presence of water and mangroves, especially the river Wouri estuary. It is common to find dwellings surrounded by scanty
or permanent water. Much of the city is less planned and is not built sustainably: less
than 8% of the total area is occupied by condominium, multi-storey, villa and single
storey, whereas mixed construction has a surface area of 23.5% and mud/wood
construction, 20.4% (CLUVA 2010). This indicates a very poor population and
hence a high pressure on natural resources and vegetation. Plantations, parks, and
agriculture cover only a little part of the area. In the face of the rapid urban expansion for the past 20 years, it is certain that the demand for sand, soils and scoria
would remain elastic. The profitability and others facilities offered by the Douala
city favored this activity and induced the increment of quarries.
Urbanization is one of the most unfavorable factors to the conservation and evolution of terrestrial ecosystems in emerging or developing countries (Fig. 3.12). The
Cameroon coast contains four major cities with mangrove stands border agglomerations from Kribi to Limbe. Mangroves of Kribi were heavily damaged by the installation of modern buildings at the seaside (Nfotabong-Atheull 2011). The construction
of tourist complexes after the realization of the asphalt road that connects Kribi to
Edea have spared no specimen of mangroves (Din 2001). The development of the
city of Tiko destroyed mangrove mainly in the old port that was certainly attracted
people in the area. The installation of new populations favored the destruction of a
major band of mangrove.
The establishment of roads inside mangroves led to an ecological fragmentation
and isolation of two sides of mangroves that can no more exchange materials
between them. The general aspect of the vegetation (composition and structure) corresponds to a senescent stand where swamp forest species gradually invade the site.
Mangrove ecosystems could survive after fragmentation if the derivative forests are
regularly watered by daily tides. The zonation and the progressive series change and
affect deeply the structure of the forest but the composition will remain unchanged
even if the structure of trees is also affected. Species like Nypa fruticans take advantage of such phenomenon to occupy more space.
Although mangroves contribute considerably to the social and economic wellbeing of the Cameroon coastal inhabitants, their total surface area has decreased by
30% in 20 years (Spalding et al. 2010), mainly due to rapid and uncontrolled urbanization around Douala city (Din et al. 2002; Ellison and Zouh 2012; NfotabongAtheull et al. 2013).
3.4.5 Wastes
Wastes and wastewater discharged into nearby mangrove forest, marshes and rivers
can finally get into the mangroves ecosystem due to rainfalls, currents and tide
movements. Direct discharges into mangroves are frequently observed in the Wouri
estuarine mangrove. The mangrove areas are daily transformed as solid and liquid
waste disposals accepted by the Douala urban council without any restriction
3 Impact of Urbanization on the Evolution of Mangrove Ecosystems…