Current status and conservation of mangroves in Africa: An overview
The inter-tidal forest communities called mangroves occurring in tropical and subtropical areas in the world cover most of the coastal regions of Africa and have been playing significant ecological, economical and socio-cultural roles in the lives of coastal communities in the continent. This paper presents an overview of current conservation status of mangroves in Africa including their coverage, biodiversity status, important threats and gaps in major conservation efforts. Recommendations are made to further combat rising threats, address sustainable use issues and restore these mangrove ecosystems.
Extent and distribution
Mangrove forests cover over 3.2 million ha in the African continent about 19% of global coverage. They are distributed in three major coastal sections: western Atlantic (1.5 million ha, 49%), central Atlantic (0.4 million ha, 14%) and eastern Indian Ocean (1.2million ha, 37%) (Figure 1). In the western Atlantic coastal section of Africa, mangroves stretch from Mauritania in the north western section of the Atlantic coast to Senegal in the Saloum Delta, Lower Casamance through Guinea Bissau, South Guinea, to the Gulf of Guinea flanking the coastlines of West and Central Africa from Liberia to Angola. Nigeria has the largest mangroves in Africa (Table 1 and Figure 2) located in the Niger delta with up to 1.0 million ha of mangrove stands in this area and plays a critical role in supporting the region’s rich wildlife. Mangrove covered countries in Eastern Africa include Somalia, Kenya, Seychelles, Tanzania, Madagascar, Mozambique and South Africa. Climatic conditions are predominantly humid and tropical but changes to more temperate conditions towards Angola and South Africa. Climatic conditions are predominantly humid and tropical but changes to more temperate conditions towards Angola. In Africa, there is some little variation in phytogeographical distribution of mangroves species across the continent. West Africa and Central Africa have three families with six species including: Avicenniaceae (Avicennia germinans – referred to as white mangroves); Combretaceae (Laguncularia racemosa, Conocarpus erectus); and Rhizophoraceae (Rhizophora harrisonii, R. mangle, R. racemosa – usually called red mangroves). R. racemosa is very dominant in this region with characteristic long and straight poles in pure stands especially in tidal estuaries. While R. harrosonii and R. mangle are small trees and shrubs respectively. In Eastern Africa there are 10 species of mangroves, the dominant species being Rhizophora mucronata, Ceriops tagal and Avicennia marina (Semesi, 1998) occupying a total of 1.1million ha (Spalding et al., 1997).
African mangroves are very diverse morphologically and in flora and fauna. A total of 17 mangrove species are found in Africa with eight species uniquely in west and central Africa while nine species are unique to eastern African costs. West and central African pure mangrove species include: Rhizophora racemosa, Rhizophora harrisonii, Rhizophora mangle; Avicennia germinans; Lagunculacia, Conocarpus erectus fern Acrostichum aureum ; and introduced palm : Nypa fucticans (Arecaceae). Pure mangrove species in eastern Africa include Avicennia marina, Avicennia officinalis, Bruguiera gymnorrhiza, Ceriops tagal, Heritiera littoralis, Lumnitzera racemosa, Rhizophora mucronata, Sonneratia alba and Xylocarpus granatum. Fauna composition is also very diverse with aquatic fauna including mammals (monkeys, antelopes, and manatees), molluscs (bivalves, oysters), crustaceans, fish; and terrestrial fauna also with mammalian, reptile and avian species especially water birds.
Mangroves are very important from various respects: biologically, with a high level of fauna biodiversity as over 80% of commercial fisheries and other aquatic species spent most or part of their life cycle in the mangroves; ecologically, they play a crucial role in fertilisation, stabilisation, filtration, regulation of microclimate and acting as food chain support and as nurseries for many fish and invertebrate species; economically, they provide a wide range of timber and non-timber forest products that support rural economies and having high ecotourism potentials.
Despite these characteristics and importance of this fragile ecosystem, African mangroves have been subjected to enormous pressures and threats within the last past decades with great losses for example over 20-30% of the mangroves in the west and central Africa have been lost in the past 25 years (Table 1). This is through many factors especially urbanisation, urban infrastructural development, quarrying, salt and sand extraction; pollution from industries, agro-industrial chemicals, petroleum and gas exploitation; absence of appropriate legislation; deforestation for fish smoking (Ajonina et Usongo, 2001 ; Ajonina et al 2005) and the proliferation of invasive species including the climate change effects accentuated by population growth. These threat factors appear to be regional from natural to human made factors with mangroves in the upper western coasts from Mauritania suffering from natural factors mainly of drought and salt intrusions. The mangroves from the gulf of guinea from Liberia to Angola suffer from fuel wood exploitation for fish smoking, wood for construction; petroleum and gas exploration and exploitation activities along the coast are also increasingly threatening these mangroves.
Eastern African mangroves also face additional threat from shrimp aquaculture from South East Asia now reaching west Africa. The major factors of loss are the spread of shrimp farms reaching now in West Africa.
The underlying root causes of mangrove degradation in Eastern Africa are associated with population pressure, poor governance, economic pressure in the rural and urban centres, poverty status of local communities and unequal distribution of resources. In addition, climate change related factors such as sea level rise and increased sedimentation have affected the fringing mangroves in Kenya, Tanzania and Mozambique (FAO, 2005). These have led to shortages of firewood and building materials, reduction in fisheries, and increased coastal erosion, loss of livelihood and increase in poverty ((Abuodha and Kairo, 2001). According to a recent assessment of global mangrove forests, Eastern Africa region has lost approximately 8% of its mangrove cover in the last 25 years on average approximately 3,000 ha per year (FAO, 2005).
General consequences of the threats
Current rates of mangrove degradation therefore seriously threaten this fragile ecosystem and reduce its resilience to mitigate climate change effects. In recent years, frequent impacts of sea surges, inundations and natural disasters recorded in the coastal areas are evidence of increased vulnerability largely attributed to human pressures. Although some governments in the region have initiated various biodiversity conservation policies, there is still inadequate provision for mangrove forests conservation. Thus maintaining a balance between the needs of the local coastal communities and the ecological potentials of the remaining mangrove ecosystems in fisheries should cause a renewed national and international ecological or economic interest for African mangrove swamps through concerted efforts.
Much efforts have been made by different actors to save these mangrove forests from further destruction: the Governments through the signature of many mangrove related legislations and international conventions including the Convention on Climate Change, the Convention on Biodiversity, the Convention on International Trade on Endangered Species, the Convention on Ozone Layer and the Ramsar Convention on the Conservation of Wetlands. Many governments have also elaborated many National Action Plans for effective implementation of these international conventions including inclusion of mangroves in protected areas where some 18 – 22 % are protected in west and central Africa (Table 1). Despite these efforts there is still not adequate policy, law and institutional provision for mangrove forests. Mangroves tend to be marginally defined and placed under many institutions with conflicting roles. For example in Cameroon it is under the responsibility of many ministries including Ministry of Forestry and Wildlife, Ministry of Environment and Nature Protection, Ministry of Tourism, Ministry of Fisheries and Animal Industries. National and international Non Governmental Organisations have also contributed through various projects and programmes on the conservation of biodiversity and sustainable management of natural resources and poverty reduction. African Mangrove Network a civil society organisation with its national focal points and operation through for example Cameroon Mangrove Network in Cameroon, Mangrove Conservation Society of Nigeria, Kwetu Center in Kenya, FACE in Liberia, AGRETAGE in Guinea etc and WAAME in Senegal hosting the Secretariat, has also been playing a prominent role in the protection of these mangroves. Most activities of the network has been largely supported by the IUCN NL (Netherlands), SSNC (Sweden) to undertake programmes ranging from mangrove regeneration, promoting income generation opportunities to management plan developments in different countries.
Conclusion and future prospects
Maintaining a balance between the needs of the local coastal communities and the ecological potentials of the remaining mangrove ecosystems is causing a renewed national and international ecological or economic interest for African mangrove swamps through already concerted efforts. These are still not enough but there is continued searching for strategies geared towards sustainable management of our mangrove forests widely degraded to near point of extinction of this rare, fragile and important ecosystem from the view point of biology, ecology and economics. The role of civil society organisation including associations, community based organisations to complement government efforts should not be overemphasised. There will be increasing role of private sector participation in the future from their passive role today. The place of research in providing needed information for management can not be overemphasised. Research should move from current descriptive nature to providing more quantitative information on the status of the resources, population dynamics and resilience to human or natural induced factors that will set sustainable use limits. Cooperation at different levels is required and the time to act to save our mangroves for further destruction is now. Let’s therefore join to save the mangroves of Africa.
By: Gordon Ajonina (1), Abdoulaye Diamé (2) and James Kairo (3)
(1)National Coordinator, Cameroon Mangrove Network
BP 54 Mouanko, Littoral Province, Cameroon
(2)Executive secretary of the AMN, POBox 26352 Dakar-Sénégal,
West Africa, firstname.lastname@example.org
(3)Mangrove System Information Service
c/o. Kenya Marine and Fisheries Research Institute
- Abuodha, P.A., Kairo, J.G. 2001 Human-induced stresses on mangrove swamps along the Kenyan coast. Hydrobiologia Vol. 458 pp. 255-265.
- Ajonina, G.N. and Usongo, L.2001. Preliminary Quantitative impact assessment of wood extraction on the mangroves of Douala-Edea forest reserve Cameroun. Tropical Biodiversity 7(2)3: 137-149.
- Ajonina, G.N., Ayissi, I. and Usongo, L. 2004. Inventory of Coastal Wetlands of Cameroon/Inventaire des Zones Humides Côtieres du Cameroun. Wetlands International Report. 68pp.
- Ajonina, P.U., Ajonina, G.N., Jin, E. Mekongo, F., Ayissi, I. and Usongo, L.2005.Gender roles and economics of exploitation, processing and marketing of bivalves and impacts on forest resources in the Douala-Edaa Wildlife Reserve, Cameroon. International Journal of Sustainable Development and World Ecology 12(2005): 161- 172
- FAO, 2005 Status and trends in mangrove area extend worldwide. Working paper No. 64. Forest Resource Division. FAO, Rome.
- Kairo, J. G., Dahdouh-Guebas, F., Bosire, J. and Koedam, N. (2001). Restoration and management of mangrove systems – a lesson for and from the East African region. South African Journal of Botany, 67: 383-389.
- Spalding, M.D., Blasco, F. and Field, C.D., eds. 1997. World Mangrove Atlas. The International Society for Mangrove Ecosystems, Okinawa, Japan. 178 pp.
- UNEP (2003). Mangroves of Eastern Africa. UNEP-Regional Seas Programme/UNEP-WCMC.
- UNEP (2007). Mangroves of Western and Central Africa. UNEP-Regional Seas Programme/UNEP-WCMC. http://www.unep-wcmc.org/resources/publications/
On WRM’s special section “African Voices on Forests” you can find further information on mangroves in several countries in the continent that our friends from the African Mangroves Network sent to share with the bulletin readers
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