Credits: Katie Fuller, 2009. Marine Photobank

Mangrove forests are considered highly productive ecosystems and most carbon is either buried in sediments locally and in adjacent systems or stored in forest biomass as the trees grow. Three different global estimates for carbon burial within mangrove systems all converge on a value equivalent to ^~18.4 x 10¹² g C yr^-1 when applying a global area of 160,000 km² (Chmura et al. 2003). In comparison to tropical forests, mangroves have actually been found to be more efficient at carbon sequestration (Laffoley and Grimsditch, 2009). Mangroves are thus clearly an option for countries interested in developing REDD+ readiness plans.

Unfortunately, it is estimated that more than 50 per cent of the world’s original mangrove forests have disappeared (Valiela et al. 2001), and the annual global rate of mangrove loss continues to be between one to two per cent (Spalding et al. 2010). In order to counteract the loss of mangrove forests and to provide incentives against deforestation, REDD+ projects could finance the protection of mangroves.

Apart from their value as carbon sinks, mangroves also provide many other socio-economic 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. Ecosystem services from mangroves thus translate directly into economic benefits (see Table 1).

However, the economic value of mangroves is usually ignored or under-valued when economic analyses are being made for coastal developments, despite the obvious economic arguments for including ecosystem services. The products and services mangroves provide are usually externalized and not accounted for. Therefore it is difficult to determine what people lose when mangroves are destroyed until it is too late, and often other coastal developments such as infrastructure or aquaculture are deemed more profitable despite evidence to the contrary. If mangroves are to become viable investment options, it is important that thorough economic evaluations be carried out for all ecosystem services.

Table1

Furthermore, globally standardized protocols for measuring, reporting, verifying (MRV) and monitoring carbon in mangroves need to be developed. In order for countries to receive REDD+ financing, they need to implement measuring and monitoring systems for assessing the amount of carbon stored in their forests. These systems need to be compliant with the good practice guidelines agreed under the IPCC.

Financing mangrove conservation through REDD+ can ‘unlock’ the huge economic value that exists in these ecosystems, therefore providing more value per ‘REDD+ dollar’ than solely from carbon sequestration. Instead of investing in expensive infrastructure, mangroves provide many of the same services for a lower price, and this needs to be recognized by local and national governments. It is clear that as developing countries with relatively extensive mangrove forests prepare for REDD+, it is critically important to include mangrove forests in their strategies. Few other forest systems offer as many benefits for climate, conservation and development. It is thus strongly recommended that national governments consider the incorporation of mangroves in their REDD+ readiness plans.

References
Chmura GL, Anisfeld SC, Cahoon DR, & Lynch JC (2003) Global carbon sequestration in tidal, saline wetland soils. Global Biogeochemical Cycles, 17, 1111.
Dittmar, T., and R.J. Lara (2001) Molecular evidence for lignin degradation in sulfate reducing mangrove sediments (Amazonia, Brazil), Geochim. Cosmochim. Acta 65, 1403–1414.
Giri, C, Ochieng, E, Tieszen, L, Zhu, Z, Singh, A, Loveland, T, Masek, J and Duke, N (2010) Status and distribution of mangrove forests of the world using earth observation satellite data. Global Ecology and Biogeography.
Kristensen E, Bouillon S, Dittmar T, & Marchand C (2008) Organic matter dynamics in mangrove ecosystems. Aquat. Bot. 89: 201-219.
Laffoley, D and Grimsditch, G (2009) The management of natural coastal carbon sinks. IUCN, 64pp.
Spalding M, Kainuma, M and Collins, L. (2010) World atlas of mangroves. UNEP-WCMC, Cambridge, 336 pp.
Valiela I, Bowen JL, & York JK (2001) Mangrove forests: one of the world’s threatened major tropical environments. BioScience 51: 807-815.

Gabriel Grimsditch is a Programme Officer for the UNEP Marine and Coastal Ecosystems Branch working on oceans and climate change, based in Nairobi, Kenya.