Carbon pools and multiple benefits

INTRODUCTION

THE ISSUES

Mangrove forests along the west coast of Central Africa, including Cameroon, Equatorial Guinea, Sao Tome and Principe, Gabon, Republic of Congo (RoC), Democratic Republic of Congo (DRC), and Angola covered approximately 4,373 km 2 in 2007; representing 12.8% of the African mangroves or 3.2% of the total mangrove area in the world (UNEP-WCMC, 2007). According to a UNEP-WCMC (2007) report, 20-30% of mangroves in Central Africa were degraded or lost between 1980 and 2000. Major threats in the region include increasing coastal populations, uncontrolled urbanization, exploitation of mangroves for firewood, housing and fishing, pollution from hydrocarbon exploitation and oil and gas exploration. The consequences of current rates of mangrove deforestation and degradation in Central Africa are important as they threaten the livelihood security of coastal people and reduce the resilience of mangroves. Recent findings indicate that mangroves sequester several times more carbon per unit area than any productive terrestrial forest (Donato et al., 2011). Although mangroves cover only around 0.7% (approximately 137,760 km 2 ) of global tropical forests (Giri et al., 2010), degradationofmangroveecosystemspotentially contributes 0.02 – 0.12 Pg carbon emissions per year, equivalent of up to 10% of total emissions fromdeforestation globally (Donato et al., 2011). In addition, mangroves provide a range of other social and environmental benefits including regulating services (protection of coastlines from storm surges, erosion and floods; land stabilization by trapping sediments; and water

quality maintenance), provisioning services (subsistence and commercial fisheries; honey; fuelwood; building materials; and traditional medicines), cultural services (tourism, recreation and spiritual appreciation) and supporting services (cycling of nutrients and habitats for species). For many communities living in their vicinity, mangroves provide a vital source of income and resources from natural products and as fishing grounds. Multiple benefits that mangrove ecosystems provide are thus remarkable for livelihoods, food security and climate change adaptation. It is no wonder that the Total Economic Value of mangroves has been estimated at USD 9,900 per ha per year by Costanza et al., (1997) or USD 27,264–35,921 per ha per year by Sathirathai and Barbier (2001). However, loss and transformation of mangrove areas in the tropics is affecting local livelihood through shortage of firewood and building poles, reduction in fisheries and increased erosion. Recent global estimates indicate that there are about 137,760 km 2 of mangrove in the world; distributed in 118 tropical and sub- tropical countries (Giri et al., 2010). The decline of these spatially limited ecosystems due to both human and natural pressures is increasing (Valiela et al., 2001; FAO, 2007; Gilman et al., 2008), thus rapidly altering the composition, structure and function of these ecosystems and their ability to provide ecosystem services (Kairo et al., 2002; Bosire et al., 2008; Duke et al., 2007). Deforestation rates of between 1-2% per year have been reported thus precipitating a global loss of 30-50% of mangrove cover over the last half century majorly due to overharvesting and land conversion (Alongi, 2002; Duke et al., 2007; Giri et al., 2010; Polidoro et al., 2010).

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