Ecology of Mangrove Growth and Recovery in the Lesser Antilles: State of Knowledge and Basis for Restoration Projects

Abstract

Whereas the increasing knowledge on tropical coastal wetlands highlights the ecological and economical importance of such ecosystems, anthropogenic activities within the coastal zone have caused substantial, irreversible losses of mangrove areas in the Lesser Antilles during the last decades. Such a paradox gives strength to compensatory policy efforts toward mangrove restoration. We review the available knowledge on the ecology of mangrove growth and recovery in the Lesser Antilles as a contribution to possible restoration projects in such islands. Distribution of species follows a general pattern of seaward/landward zonation according to their respective tolerance to flooding and to pore‐water salinity. An experimental study of seedling growth following simulated oil spill has documented the tolerance of Rhizophora mangle and Avicennia germinans seedlings to oil concentration in soils and the effects of natural biotic and abiotic factors on seedlings growth and survival. Monitoring mangrove recovery following hurricane Hugo has given information on growth patterns, from seedling to sapling stages, according to species and site conditions. Forest recovery was mostly due to pre‐established seedlings. For the large Rhizophora propagules, buoyancy appears to be a quite inefficient way of dispersal far inland from the sea shore or riversides. Causes of recovery failure are discussed. From these results we attempt to answer the questions when, where, how to plant mangroves, and what species to use.

Local positive feedback and the persistence and recovery of fringe Avicennia marina (Forssk.) vierh. mangroves

“…Buoyancy is regarded as an important factor as well as the period of obligate dispersal and anchoring time (Clarke and Myerscough 1991;Clarke 1993;Delgado et al 2001). A. marina propagules have an obligatory dispersal period of around 10 days (Clarke 1993;Clarke et al 2001;Hogarth 1999 (Clarke 1995). Mangroves may be able to reproduce around their fifth year.…”

“…We assume that elevation follows a simple linear slope from sea to shore along the x coordinates. Mangroves occur in the tidal regions and their shore-ward limit can be adequately described by spring high-water (De Boer et al 2000;Hogarth 1999). Hence, the system's upper boundary (H max ) is set 0.2 m above the highest spring tide and its lower boundary (H min ) 0.2 m lower than the lowest neap:…”

“…Kitaya et al (2002) measured seedling mortality on different elevations on tidal flats, and found that mortality varies strongly with elevation. Elevation correlates strongly with wave action, inundation and other related factors such as pH (Hogarth 1999). The mortality rates of seedlings can thus be represented using the relationship between elevation and mortality.…”

“…Research on mangroves has focused on zonation patterns (Bunt 1996;Ellison et al 2000;Hogarth 1999), and on relations between gradients of abiotic factors, such as salinity, and species occurrence (Blasco et al 1996;Delgado et al 2001;Hogarth 1999). Recently the decrease of mangroves (Alongi 2002;Ellison 2000) has triggered a number of studies aimed at unravelling the factors that are responsible for differences in the spatial distribution of mangroves, which could ultimately be used for restoration purposes (Bosire et al 2008;Ellison 2000;Hogarth 1999;Imbert et al 2000;Riley and Kent 1999;Twilley et al 1998;Walters 2004). In restoration it is important to understand which factors determine whether or not a certain area will allow successful reforestation.…”

Natural and anthropogenic changes to mangrove distributions in the Pioneer River Estuary (QLD, Australia)

“…Other changes, such as hydrological alterations, manifest as indirect effects of human activity: for example, the topdying of Heritiera fomes in the Ganges Delta is likely to be a result of construction of embankments (Spalding et al 1997). Other changes result from distinctly natural processes, such as extensive mangrove loss in the Lesser Antilles from hurricane damage (Imbert et al 1996;Imbert et al 2000) or rapid losses/gains from cycles of erosion and accretion at the Amazon River delta (Fromard et al 2004). Because some types of change are more likely to destabilize mangrove ecosystems and impact mangrove ecosystem services (e.g.…”