Palmier d'eau

As this species prefers more freshwater environments, hyper-saline conditions and strong wave action (including that caused by passing ships) can threaten this species. Although local estimates are uncertain due to differing legislative definitions of what is a 'mangrove' and to the imprecision in determining mangrove area, current consensus estimates of mangrove loss in the last quarter-century report an approximately 20% decline in mangrove areas in countries within this species range since 1980 (FAO 2007).

Sea level rise is a major threat, especially to back mangroves that have no area in which to expand. Mangrove species with a habitat on the landward margin may be particularly vulnerable to sea-level rise if owing to coastal development their movement inland is blocked. In the Sunderbans Delta of India, for example, which has a relatively high rate of sea-level rise, provides insight to what may be common elsewhere as global sea levels rise (Mukherjee 1984). There, Nypa fruticans is blocked from inland migration owing to coastal development, and its area and occurrence has been declining (K. Kathiresan pers. comm.)

All mangrove ecosystems occur within mean sea level and high tidal elevations, and have distinct species zonations that are controlled by the elevation of the substrate relative to mean sea level. This is because of associated variation in frequency of elevation, salinity and wave action (Duke et al. 1998). With rise in sea-level, the habitat requirements of each species will be disrupted, and species zones will suffer mortality at their present locations and re-establish at higher elevations in areas that were previously landward zones (Ellison 2005). If sea-level rise is a continued trend over this century, then there will be continued mortality and re-establishment of species zones. However, species that are easily dispersed and fast growing/fast producing will cope better than those which are slower growing and slower to reproduce.

In addition, mangrove area is declining globally due to a number of localized threats. The main threat is habitat destruction and removal of mangrove areas. Reasons for removal include cleared for shrimp farms, agriculture, fish ponds, rice production and salt pans, and for the development of urban and industrial areas, road construction, coconut plantations, ports, airports, and tourist resorts. Other threats include pollution from sewage effluents, solid wastes, siltation, oil, and agricultural and urban runoff. Climate change is also thought to be a threat, particularly at the edges of a species range. Natural threats include cyclones, hurricane and tsunamis.

There are no conservation measures specific to this species, but its range may include some marine and coastal protected areas. Continued monitoring and research is recommended, as well as the inclusion of mangrove areas in marine and coastal protected areas.