Habitat and Ecology
In Northern Brazil, mangrove swamps dominated by A. schaueriana provide critical habitat for the mangrove crab Ucides cordatus. This crab is collected both for subsistence use and for regional/national markets. In some areas of northern Brazil, community-based initiatives are effectively managing the crab harvest and the mangrove forests. However, in other areas, the crabs are overharvested and the mangroves are being cut relatively rapidly, further reducing habitat for the crabs (Diele et al. 2005, Glaser and Diele 2004).
IUCN Red List Assessment
Red List Category
Red List Criteria
Genetic studies of Avicennia are numerous as microsatellite loci, RAPDs, and AFLPs have been developed for this species (Ceron-Souza et al. 2006). Eastern and western Atlantic provenances of Avicennia show significant genetic differentiation, as indicated by leaf chemistry (Dodd and Bousquet-Melou 2000). Studies to date show well-defined genetic structure differentiating western Atlantic from Pacific populations across the isthmus of Panama (Dodd et al. 2002) and among populations sharing a coastline (Ceron-Souza et al. 2005).
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/ ast 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.
Research is needed to establish a minimum viable population size for the taxon. Demographic modeling could also be useful. Research on exploitation and impacts of harvesting on populations is needed. More cost/benefit analyses of mangrove conversion, particularly in Brazil, are critical because the mangrove crab (Ucides cordatus) is extensively harvested from intact mangroves for subsistence and regional markets.
New Landsat and IKONOS technology can and should be used to conduct species-based, landscape-level monitoring of deforestation (Kovacs et al. 2005). More research is needed to document Avicennia's influences on water quality, erosion control and pollution buffering. All conservation of Avicennia (indeed, any mangrove species) needs to be undertaken at the habitat level.