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Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems

TDA-IME Project Final Report June, 2013 determine mangrove structure also function at the ecosystem level (Hutchins and Saenger, 1987; Robertson and Alongi 1992). TABLE 5: Benefits people derive from mangrove ecosystems. Group Benefits (Goods and Services) Regulating services: Protection of beaches and coastlines from storm surges, waves, and floods; reduction of beach and soil erosion; stabilization of land by trapping sediments; water quality maintenance; sequestration of carbon dioxide; and climate regulation 17 Provisioning services: Subsistence and commercial fisheries (food, habitat, and nursery grounds for aquatic life), aquaculture, honey, fuel wood, timber and other building materials, and traditional food and medicines Cultural services: Tourism and recreation, and spiritual appreciation Supporting services: Cycling of nutrients, and habitats for species Adapted from the Millenium Environment Assessment (2005). While few would doubt the need to adopt an ecosystem-based approach to mangrove conservation and sustainable management, there is still today some confusion over what “true mangroves” are and what constitute “mangrove associates”? This distinction refers mainly to the mangrove plant community, because nearly all the mangrove animals are, de facto, associates (e.g. Soegiarto, 1999). Many species of birds, insects, mammals, fish and crustaceans use the mangrove forest opportunistically as their preferred, but not sole habitat. The mud lobster (Thalassina anomala) (Havanond, 2000) and the crab-eating frog (Rana cancrivora) (Hutchins and Saenger,1987) may be regarded as two of the few exclusive mangrove animals in Asia. In describing the mangrove flora, Tomlinson (1986) noted that true mangroves “form forests with no understory except their own seedlings”. The most useful, short definition of true mangroves is considered here to be the one given by Saenger (2002): "A mangrove is a higher plant (tree, shrub, palm, herb or fern) which (1) predominantly grows in the intertidal areas of tropical and subtropical shorelines, which (2) exhibits a marked degree of tolerance to high salt concentrations and soil anoxia, and which (3) has propagules able to survive dispersal by seawater." Tomlinson (1986) commented that Nypa is the only genus of palm with a viviparous fruit, indicating a mangrove-like specialization, a characteristic which also fits with Saenger’s definition of true mangroves. The mangrove-associated fern Acrostichum is also included, as it can be the dominant vegetation in disturbed back mangroves, or in mangroves with high elevation caused by the mound-building activities of mud lobsters (Havanond, 1987, 2000; Havanond and Aksornkoae, 1989). Similarly, three species of Acanthus (or “mangrove thistle”) are included, because this voracious climber is also typical of back-mangroves and disturbed sites with a high elevation. Excluded from Tomlinson’s definition of mangrove-associates are herbaceous or semi-woody plants that form the fringing coastal vegetation near true mangroves, and along sandy beaches; these include genera such as Ipomea, Pluchea and Sesuvium, plus grasses, rushes and sedges. However, these plants have great invasive capacity when mangrove forests become degraded and may therefore be useful indicators of mangrove habitat disturbance.


Transboundary Diagnostic Analysis of Indochina Mangrove Ecosystems
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