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Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems

TDA-IME Project Final Report June, 2013 serious gap in our understanding of how different species might be able to adapt to sea level rise. It is also highly relevant to mangrove rehabilitation - it would make sense to plant with species that are better able to adapt to rising sea level, provided of course, that they are also sufficiently suited to present hydrological conditions. Forest Biomass, Growth and Carbon Storage There is a large body of literature on the measurement of mangrove forest biomass and productivity, much of which is summarised by Komiyama et al. (2008). Other significant recent publications on mangrove biomass and carbon storage include Cole et al. (1999), Bouillon et al. (2008), Kauffman and Cole (2010), Donato et al. (2011) and Kauffman et al. (2011). In well-developed, closed-canopy mangrove forests, total above-ground biomass normally ranges up to around 650 t ha-1, depending on species composition, age and stand density (Komiyama et al., 2008). One stand dominated by Sonneratia and Bruguiera on the West- Pacific island of Yap has been reported to have an above-ground biomass of over 800 t ha-1 (Donato et al., 2011). Below-ground root biomass estimates are much less certain because of the difficulty of representative sampling; and also of distinguishing between living and dead roots, and other sediment detritus. Nonetheless, with the sole exception of Rhizophora apiculata monoculture plantations (Ong et al., 2004), below-ground root biomass is usually somewhat higher than above-ground biomass, indicating that mangroves as a group (with the possible exception of Rhizophora spp.) invest a great deal of carbon in building underground root systems. This feature of mangrove forests explains their acknowledged importance for carbon sequestration as a climate change mitigation response (Donato, et al., 2011). Mangrove Fauna Crustaceans and Molluscs Mangroves support a rich macro- and meio-fauna, consisting of terrestrial and aquatic (marine and freshwater groups) that include both resident and temporary resident species (Macintosh and Ashton, 2002). Faunal diversity is correlated with the high plant and habitat diversity found in the Indo-West Pacific mangroves (Jones, 1984; Reid, 1986; Ricklefs and Latham, 1993; Lee, 1998). Thus, the Indochina mangrove ecosystems are an important refugium for mangrove animals, as well as plants. A number of animals that depend on mangrove ecosystems are at risk and have been recognized in the IUCN Red List (Table 9). However, a large number of animal species related to mangroves are data deficient and thus cannot be assigned a risk status. Table 9 could be expanded considerably, but only large, well known species are included. Further research is required to fill gaps in our knowledge of these species. Mangrove habitat loss through conversion and human encroachment is a primary cause of their decline. These impacts on wildlife are likely to continue and increase as human population pressure intensifies. A crucial aspect of faunal biodiversity for transboundary mangrove management is that many species, among them crustaceans, fish, mammals and birds, use the mangrove forest ecosystem during only part of their life-cycle. The level of mangrove dependency varies depending on the species and its life cycle characteristics (Manson et al., 2005). Thus, the mangrove habitat supports many more species as visitors, or indirectly (e.g. via coastal food chains). These important support functions must be taken into account when planning conservation measures (Macintosh and Ashton, 2002). Clearly, transboundary mangrove areas can assist greatly in supporting migratory species in particular (Semmens et al., 2011). The dominant macrofauna components in terms of numbers and species in the mangrove ecosystem are crustaceans and molluscs (e.g. Sasekumar, 1974; Jones, 1984). These two 35


Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems
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