Mangrove Recovery Research Articles

Comparative study of mangrove recruitment in oil deforested areas in Guimaras, Philippines

ABSTRACT The MT Solar I oil spill that released over 2 million liters of bunker C oil in Guimaras in August 2006 affected mangrove forest in varying degrees from acute damages, sublethal stresses and long term effects. Although the incident caused only <1 ha deforestation, large scale mangrove planting has been implemented as part of response initiatives without inference to scientific assessment of the natural recovery potential of the damaged habitat. The response and intervention in the aftermath of the oil spill primarily involved planting mangroves. This study assessed the mangrove recruitment and colonization in two deforested mangrove areas in Guimaras, Philippines and evaluated whether replanting was necessary as part of intervention. Results on reconstructed age extrapolated from the internodal index showed that recruitment started to take place one and two years after the spill in Site 1 (3.33% of tagged wildings) and Site 2 (11.67%) respectively. However, the wilding establishment in the former site was impaired in the succeeding years and maintained at very low numbers (0.07–0.15 m−2) whereas wilding establishment was high in Site 2 (2.19–3.31 per m−2). The difference between sites is statistically significant (P<0.0001). The marked difference between sites is attributed to the prevailing interventions and persistent disturbances. The extraction of dead trees and downed wood in Site 1 impaired the progress of recovery and was further compounded by persistent disturbances brought by the socioeconomic activities, whereas, non-intervention in Site 2 favored the progress of natural recovery. Eight years after the incident, the colonizers in Site 2 were already reproductively mature as some already developed flowers. This study highlighted the capacity of mangroves to recover from perturbations as long as the geomorphological features of the habitats are not altered. The large-scale mangrove planting implemented in the affected areas is deemed unnecessary given that one year after the incident recruitment started to progress. Thus, future oil spill responses and interventions should carefully assess the natural recovery processes of the impacted areas first, before proceeding to large scale mangrove planting programs. Otherwise, the good intentions of implementing faster recovery of mangroves and other impacted habitats may be considered a waste of public funds and a futile effort vis-à-vis practicality.

Damage Assessment and Recovery Monitoring of the Mangrove Forests in Calauit Island Affected by Typhoon Yolanda (Haiyan)

Calauit island is one of the islands in the Calamian Group of Islands in northern Palawan. The island is truly blessed with bountiful mangrove resources which provide the Tagbanuas enormous economic and ecological importance. Not known to many, Calauit island became the exit point of typhoon Yolanda causing tremendous damage to mangrove area. The study assessed the extent of damage and the recovery potential of Calauit mangrove forests from the devastation of Typhoon Yolanda. Ten sampling quadrats were established in areas where trees were observed to be 100% defoliated. Individual trees (≥ 1cm diameter) inside each quadrat were measured and evaluated based on the assessment matrix developed in this study. Results of our assessment revealed serious damage of mangroves in Calauit island. About 60% of the mangrove forests was severely affected by Typhoon Yolanda. Eight months after the typhoon, 21% of the trees have fully-recovered crown (all branches were able to develop leaves), 70% are still defoliated and 22% were already dead. Four of the 10 quadrats showed high potential for recovery as evidenced by a lot of seedlings (≥ 25 seedlings) to serve as new regenerations. Conversely, there are four quadrats without any seedling recorded. Three monitoring plots were established for continuous monitoring of the recovery of the mangrove ecosystems. A course of actions was recommended to facilitate the recovery of mangroves in Caluit island, and to bring back the economic benefits from the forest.

Restoration versus natural regeneration in a neotropical mangrove: Effects on plant biomass and crab communities

Mangrove restoration is a powerful tool for reconstructing degraded tropical estuaries worldwide. The level of intervention necessary for rebuilding a mangrove area is still under study because this system is quite dynamic and some degraded areas are able to recover by themselves. We compared a Restored Area planted with Rhizophora mangle and a Self-recovered Area, to investigate how they would differ in respect to their plant and crab assemblages. In each area, 10 plots were randomly sampled for measuring tree richness, density, diameter at breast height and biomass, as well as crab richness and density after five years from recover. Plant height and biomass, as well as crab density, were significantly higher in the Restored in relation to the Self-recovered Area. However, tree richness was higher in the Self-recovered Area and crab assemblage reached in five years a similar composition in assisted, naturally recovered and natural areas, showing the high resilience of this important functional group. Active planting of R. mangle propagules can significantly improve mangrove recovery in sites with high propagule predation, increasing tree biomass and accelerating the return of animal functional groups such as crabs. However, if resources for active restoration are scarce, passive recovery can be a successful low cost alternative for mangrove restoration that preserves tree diversity and crab assemblages.

Mangrove history during middle- and late-Holocene in Pacific south-eastern Mexico

A paleoecological analysis of a 6-m-long sedimentary sequence from the La Encrucijada Biosphere Reserve (RBLE) from southern Pacific Mexico provides detailed information about past vegetation changes between ~6200 and 700 cal. yr BP. Highest percentages of mangrove pollen in pollen zone I (from ~6200 to 5400 cal. yr BP) suggest moister and warmer conditions than at present related with global rates of sea-level rise and northward position of the Intertropical Convergence Zone (ITCZ), suppressing El Niño-Southern Oscillation (ENSO) events. Drier conditions and decreasing rates of sea-level rise at ~5400–4500 cal. yr BP are evidenced in pollen zone II by the lowest percentages of mangrove pollen and highest presence of disturbance pollen. Recovery of mangroves and tropical forests occurred from ~4500 cal. yr BP, suggesting moister conditions. Agricultural activities are recorded around ~4900, 4700 and 2400 cal. yr BP, although human occupation was scarce in the mangrove area. ENSO variability correlates to mangrove pollen variation between 3600 and 2400 cal. yr BP. A protracted drought is observed at ~1300–700 cal. yr BP characterized by proportions in montane forest pollen and may be related with southern oscillation of the ITCZ and the Classical Mayan Demise.

Managing urban coastal areas through landscape metrics: An assessment of Mumbai's mangrove system

The loss of coastal landscapes resulting from urban sprawl has become a growing concern that is difficult to manage. The consequences of sprawl are often lasting, leading to the irreversible loss of vulnerable and valuable natural landscapes in favour of urban land. In this paper I analyse the spatiotemporal differences of the urban footprint in Mumbai, India, and compare these changes to the existent mangrove systems in the coastal stretches of metropolitan Mumbai. Based on the extracted urban footprint of the coastal mangrove regions, landscape metrics are performed to understand the impacts of urbanisation on the relative increase and decrease of mangrove systems. Of the entire mangrove system in the Mumbai Metropolitan Area, 36% has been lost to urban land since 1973. Over the four time periods studied, an area of urban sprawl comprises the southeastern border of Mumbai, where, since 2000, pressure on the wetlands has been largely aggravated. The high correlation of coastal stretches and urbanisation is one of the main reasons for the current fragile state of Mumbai's mangroves. A combination of a decrease and an increase in mangrove sites suggests that certain urban typologies, such as denser urban areas and older urban regions, are more prone to mangrove recovery, whereas unplanned urban settlements and highly fragmented urban areas lead to a less favourable mangrove landscape. A spatial accounting of the distribution of landscape metrics is proposed in this paper to understand land use transitions where (1) a significant increase of dense urban areas along Mumbai's fragile coastal stretches is reported; (2) this loss of mangroves is underpinned by urban typology over time; and (3) a combination of metrics vis-à-vis zones where mangroves increase and decrease are spatially and temporally addressed. With the increase in economic development that Mumbai has exhibited in recent decades, it is important to monitor the impacts on natural regions. This is a challenging task where spatial metrics combined with urban footprints may lead to a better understanding of the environmental impacts on coastal stretches. The current planning policies suggest that attention has been given to the mangrove systems of the MMR, equating to beneficial results if economic prosperity and preservation measures in Mumbai continue to take place.

Trapping of Rhizophora mangle Propagules by Coexisting Early Successional Species

Distributions of mangroves in coastal wetlands are influenced by abiotic conditions and the net effect of biotic interactions, including competition, facilitation, and consumer pressure. In coastal wetlands, early successional shrubs, herbs, and grasses may facilitate recruitment of mangroves through multiple mechanisms, including amelioration of environmental conditions, propagule trapping, and structural support. In Mosquito Lagoon, FL, we observed an aggregated distribution of Rhizophora mangle propagules along vegetated shorelines with Batis maritima and Sarcocornia perennis and hypothesized that this distribution was a result of propagule trapping by the vegetation. We designed a field experiment to evaluate retention of R. mangle propagules on vegetated and unvegetated shorelines in Mosquito Lagoon. Significant differences were found in the retention time of mangrove propagules at each shoreline type, with vegetated shorelines retaining propagules significantly longer than unvegetated shorelines. Results from this study help to define facilitative mechanisms which may be important in successional processes of coastal wetlands and have direct restoration applications. Successful recovery of mangroves at restoration sites may be facilitated by establishment of B. maritima and S. perennis, when natural propagule sources are available, or through planting mangrove seedlings into existing stands of these halophytes when restoration areas are propagule-limited.

Mangrove Evolution in Mayotte Island, Indian Ocean: A 60-year Synopsis Based on Aerial Photographs

The Island of Mayotte, in the Indian Ocean, is characterized by a highly diversified shoreline comprising numerous mangrove zones set within a vast coral reef and lagoon complex. An analysis of aerial photographs covering the period from 1950 to 2011 shows marked variability in the evolution of these mangroves and clear spatial differences in the dynamics of these communities over the 60-year period of analysis. The northern part of the island shows stability or a slight increase in mangrove area whereas the southern and western shores of the island have been characterized by a clear regression in mangroves. The total surface area of mangroves on Mayotte (7.03 km2 in 2011) has diminished overall by about 5 %, a relatively moderate figure relative to the world context of increasing diminution of mangrove area. The pattern of evolution of mangroves in Mayotte is explained jointly by development pressures on the coast and spatial variability in mangrove recovery determined by hydrological conditions and exposure to waves on this reef-fringed island. Mayotte Island acquired the status of a French administrative department in 2011 subject to both French and European Community legislation on the environment. In consequence, mangroves are now much better protected from future urbanization.

Assessment of Mangrove Recovery in Cyclone-Affected Areas of the Ayeyarwady Delta, Myanmar

Assessment of Mangrove Recovery in Cyclone-Affected Areas of the Ayeyarwady Delta, Myanmar

Restoration and recovery of hurricane-damaged mangroves using the knickpoint retreat effect and tides as dredging tools

In 2001, a hurricane moved a large sand dune, blocking the sole outlet channel of a mangrove. In the absence of daily tidal flow, the two ponds containing the mangrove vegetation evaporated, the secondary drainage channels were lost, and a salt crust formed on the bed of the ponds. The mangrove lost most of its trees and the remaining suffered from osmotic shock that led to defoliation. Restoration involved creating a knickpoint retreat (waterfall retreat effect) and tidal flow as a dredging mechanism to restore the outlet and form secondary channels in the ponds. During a very low tide, we deepened the mouth of the outlet channel by 1 m below high tide level to form a small waterfall when high tides receded. During successive tides, this one-step knickpoint deteriorated and formed a series of low rapids. With a steep gradient, the rapids retreated upstream into the ponds, first reopening the outlet channel and then carving new secondary channels in the pond mud flat. The excavation process of the outlet channel was repeated three times and was sufficient to effectively improve the hydrology of the entire pond system; allowing adequate flooding and draining of the mangrove ponds. Hydrology analysis tested by the Engelund–Hansen sediment transport formula established that the output of sediment from the ecosystem is greater than the input of sand into the mangroves. This is keeping the main channel continuously open. After eight years, tidal flow continues to keep the channels open; the salt crust has disappeared; the trees have recovered, and a large area of new vegetation has emerged.

Contrasting responses of two Caribbean mangroves to sea-level rise in the Guajira Peninsula (Colombian Caribbean)

Local geomorphology plays an important role in the response of mangrove communities to both sea-level rise and precipitation changes, mostly because it exerts an important control of the erosion–progradation balance. Here we present contrasting changes in the palynological records of two sediment cores retrieved from locations occupied by mangroves in the northeastern Caribbean coast of Colombia: Calancala and Navío Quebrado. Sediments were treated with standard procedures used in palynologycal analysis, and dated with AMS 14C and 210Pb. Age-depth models of both cores were constructed by linear interpolation between dated samples. The main modern differences between the studied sites are fresh water availability and sediment supply throughout the year. While Calancala, located at the Ranchería River Delta, has direct fresh water influence throughout the year, coastal lagoon Navío Quebrado is only sporadically influenced by fresh water sources. According to our findings, two main factors contributed to mangrove establishment in the Colombian Caribbean: i) high and accelerated sea-level rise around 6000calyr BP originating coastal lagoons that favored mangrove establishment, and ii) marine still stand and high precipitation around 3000calyr BP leading to a second wave of mangrove expansion. A drought between about 2850 and 2450calyr BP and the strengthening of easterly trade winds caused a change from Rhizophora-dominated to Avicennia-dominated stands. Increased precipitation after 2500calyr BP and subsequent increase of fluvial sediment input promoted recovery of Rhizophora-dominated mangroves. Sea-level rise during the last 150yr has caused landward mangrove expansions in deltas and progradation of coastal environments. However, the general pattern shows a net loss of mangrove vegetation as the result of coastal erosion.

Geoinformatics in mangrove monitoring: damage and recovery after the 2004 Indian Ocean tsunami in Phang Nga, Thailand

Abstract. In the aftermath of the 2004 Indian Ocean Tsunami, it has been proven that mangrove ecosystems provide protection against coastal disasters by acting as bioshields. Satellite data have been effectively used to detect, assess, and monitor the changes in mangroves during the pre- and post- tsunami periods. However, not much information regarding mangrove restoration or reforestation is available. Rather than undertaking time-consuming fieldwork, this study proposed using geoinformatic technologies such as Remote Sensing (RS), Geographic Information System (GIS), and Global Positioning System (GPS) to monitor the mangrove recovery. The analysis focused only on the tsunami-impacted mangrove areas along the western coast of the Tai Muang, Takuapa and Khuraburi Districts of Phang Nga Province, southern region of Thailand. The results consisted of 2 parts, first: the supervised classification of main land uses, namely forest, mangrove, agricultural land, built-up area, bare soil, water body, and miscellaneous covers in ASTER images, was conducted using the maximum likelihood method with higher than 75 % for overall accuracy. Once the confusion between classes was improved in post-processing, the accuracy of mangrove class was greater than 85 % for all dates. The results showed that the mangrove area in 2005 was reduced by approximately 5 % (1054.5 ha) from 2003 due to the impact of the 2004 Indian Ocean Tsunami. Although the recovery program (replacing the same species of dead mangrove trees, mainly the Rhizophora apiculata Bl and Rhizophora mucronata Poir, in situ) had started by mid-2005, the areas gradually decreased to approximately 7–8 % in 2006 and 2010 compared with the reference year of 2003. Second, the recovery trend was observed in the Normalized Difference Vegetation Index (NDVI) fluctuation curve and the supporting field survey data. The recovery patterns were summarized into 2 categories: (i) gradually recovery, and (ii) fluctuating recovery. The gradually recovery category that implied the homogeneous pattern or uniform reforestation was observed in the seriously damaged area where most of the mangrove trees were swept away during the tsunami. This pattern covered approximately 50.35 % of the total reforested area. The NDVI time series of the uniform or homogeneous reforested mangrove at the sampled plots has gradually increased after 2005. The fluctuating recovery category that implied the heterogeneous pattern or non-uniform reforestation was observed in partially damaged areas where some of the mangrove trees were swept away and broken but still some trees were remained in the area. The heterogeneous patterns covered approximately 49.65 % of the total reforested area.

Monitoring of the impacts, responses, and recovery of mangroves affected by M/T Solar I oil spill in Guimaras, Philippines

Abstract The M/T Solar I oil spill on August 11, 2006 in Guimaras released more than 2 million liters of Bunker C affected the environmentally critical areas including mangroves. Acute effects involved massive mortality of mangroves that accounted to 0.932 ha in 2006. This paper reports the monitoring studies from August 2006 to May 2010 within Taklong Island National Marine Reserve (TINMR) in Nueva Valencia, Guimaras, Philippines. Total petroleum hydrocarbons (TPHs) in mangrove sediment showed a rapid degree of weathering to evaporative loss and microbial degradation. Oil spill heavily impacted site have “high recovery potential” given that hydrocarbon in sediments showed a rapid degradation and is now within the safe limits based on National Oceanic and Atmospheric Administration (NOAA) standard. There's an improvement in mangrove community structure, however it remains a question to be taken conclusively as a sign of “recovery” considering monthly and yearly variations, thus, the need of a continued mo...

Mapping and Monitoring Louisiana's Mangroves in the Aftermath of the 2010 Gulf of Mexico Oil Spill

GIRI, C.; LONG, J., and TIESZEN, L., 2011. Mapping and monitoring Louisiana’s mangroves in the aftermath of the 2010 Gulf of Mexico oil spill. Journal of Coastal Research, 27(6), 1059–1064. West Palm Beach (Florida), ISSN 0749-0208. Information regarding the present condition, historical status, and dynamics of mangrove forests is needed to study the impacts of the Gulf of Mexico oil spill and other stressors affecting mangrove ecosystems. Such information is unavailable for Louisiana at sufficient spatial and thematic detail. We prepared mangrove forest distribution maps of Louisiana (prior to the oil spill) at 1 m and 30 m spatial resolution using aerial photographs and Landsat satellite data, respectively. Image classification was performed using a decision-tree classification approach. We also prepared land-cover change pairs for 1983, 1984, and every 2 y from 1984 to 2010 depicting ‘‘ecosystem shifts’’ (e.g., expansion, retraction, and disappearance). This new spatiotemporal information could be used to assess short-term and long-term impacts of the oil spill on mangroves. Finally, we propose an operational methodology based on remote sensing (Landsat, Advanced Spaceborne Thermal Emission and Reflection Radiometer [ASTER], hyperspectral, light detection and ranging [LIDAR], aerial photographs, and field inventory data) to monitor the existing and emerging mangrove areas and their disturbance and regrowth patterns. Several parameters such as spatial distribution, ecosystem shifts, species composition, and tree height/biomass could be measured to assess the impact of the oil spill and mangrove recovery and restoration. Future research priorities will be to quantify the impacts and recovery of mangroves considering multiple stressors and perturbations, including oil spill, winter freeze, sea-level rise, land subsidence, and land-use/land-cover change for the entire Gulf Coast. www.JCRonline.org

The Effects of Reduced Tidal Flushing on Mangrove Structure and Function Across a Disturbance Gradient

The effects of reduced tidal flushing on post-hurricane mangrove recovery were measured across a gradient of hurricane disturbance (in order of decreasing wind intensity: Captiva, North Sanibel, Central Sanibel, and East Sanibel). Each region consisted of replicate study plots with either reduced tidal exchange (tidally restricted location) or an open tidal connection (tidally unrestricted location). Locations with reduced tidal exchange displayed significantly lower (two-way ANOVA, p ≤ 0.0001) tidal amplitude, decreased seedling densities, and decreased productivity (recruitment, growth, and litter fall) when compared to the tidally unrestricted locations. Results also indicated significant regional variations in measures of mangrove stand structure (seedlings and canopy) and productivity (recruitment, growth, and litter fall) up to 4-years post-hurricane disturbance. These findings suggest that the legacy effects from hurricane disturbance vary with degree of wind intensity, acting both independently and synergistically with the effects of tidal restriction to influence post-hurricane mangrove structure and function.

The Biogeomorphology of Mangroves and Their Role in Natural Hazards Mitigation

AbstractAlong low‐relief coasts in tropical regions, mangroves occupy the biogeographical landscape usually occupied by salt‐marsh or cypress ecosystems in more temperate regions. Over 50 species of mangroves are found worldwide. In tropical regions, mangroves are the prevalent coastal wetland ecosystem, overshadowed in the public mind by tropical rainforests and coral reefs. Mangroves exist on the tropical rims of all continents except Antarctica. Numerous species of mangroves exist; collectively they create large ecosystems such as the Sundarbans in Bangladesh and India that provide habitats for endangered species, including the Bengal Tiger. As biogeomorphological agents, mangroves interact with tidal flows to entrap and stabilize sediment, create humus, and alter tropical coastal environments. Mangrove sediments and pollen entrapped therein record substantial sea‐level rises and falls during the Holocene, including a mid‐Holocene highstand, and a regression associated with the Little Ice Age. Mangroves provide habitats for a variety of coastal creatures, including crabs, juvenile fish, and sponges. Worldwide, the mangrove ecosystem is threatened by anthropogenic activities such as aquaculture, urban development, and forestry. Removal of mangroves not only endangers sensitive ecosystems, but also reduces the protection from natural hazards that mangroves offer. Tsunami and storm surges from tropical cyclones are dissipated by the intertwined root systems of the mangroves, limiting the destructive potential of the surging water, although the extent of protection offered by mangroves is controversial. The natural protection of the mangroves has proven superior to man‐made objects to deflect tsunami and storm surge. Mangrove revegetation efforts are underway in numerous countries, most notably Bangladesh, Vietnam, Thailand, and Tanzania. A variety of remote‐sensing platforms provide the ability to monitor mangrove recovery or decline around the world. The ultimate results of anthropogenic influences on mangroves remain to be seen.

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

While mangrove restoration efforts are reasonably successful, failure often occurs in high wave energy situations. Due to differences in wave energy, seedling mortality rates vary strongly with position on the intertidal flat between high water spring and high water neap elevations. However, a local positive feedback can be present between the pneumatophores of adult mangroves and the survival of mangrove seedlings to trigger recovery. In this study, a mangrove population of Avicennia marina is modelled to determine the effects of seedling mortality and local positive feedback on mangrove recovery. The model uses life history data and dispersal to simulate population dynamics. The mangrove range limits are determined by high water spring and high water neap levels. The results indicate that within these limits mangrove populations with life-history parameter values as derived from literature are indeed capable of fast growth under conditions with low seedling mortality. Local positive feedback has then a small positive influence on population recovery after mangrove loss. If, however, mortality rates increase, such as in high wave energy situations, the importance of a positive feedback increases. The model shows that a positive feedback may, given high seedling mortality rates, be an important factor for mangrove recovery. While a positive feedback may enable mangrove persistence in unfavourable conditions, destruction of adult mangroves can remove the positive feedback, which would render the system uninhabitable and practically prohibits reforestation of such areas. The model results and the presence of positive feedbacks and their importance for population dynamics in harsh conditions indicate that investigating and understanding possible feedbacks could be crucial for successful restoration efforts.

Recuperação de manguezais: um estudo de caso na baixada santista de São Paulo, Brasil

We wanted to know about the possibility of mangrove recovery in Cubatao, Baixada Santista, Sao Paulo. We planted propagules and transplanted seedlings of Rhizophora mangle in three experiment stands in Cubatao. The results showed higher survival and development in two stands. After, we made preliminaries plantations with another specie of mangrove Laguncularia racemosa. Then, we and local fisherman community planted R. mangle in bigger stands. The results and conclusions of this job are important for contribute politics of development and preservation in Baixada Santista, Sao Paulo.

Spill Response that Benefits the Long-Term Recovery of Oiled Mangroves

ABSTRACT We revisited three sites in Florida and Puerto Rico that were oiled 23 to 29 years ago, analyzing them and the published literature to determine that mangroves follow a 6 to 25 year recovery cycle. We reviewed response methods and determined that the use of offshore dispersants, the booming of tidal creeks and inlets, the use of onshore sorbents, low-pressure flushing and the manual collection of oily debris provide benefits for recovery at least in the short term. Non-beneficial response efforts that have degraded mangroves include forest cutting, heavy equipment and personnel traffic, tree burning, onshore use of chemicals, and plantings in toxic soil. Perhaps the most detrimental response effort studied was the impoundment of basin forests that has resulted in long-term losses and slow recovery rates. The intertidal use of dispersants has been shown to be beneficial to mangroves, however their use has also caused damages to nearshore environments such as coral reefs. In summary, once the oil has reached sheltered mangrove forests there exist only short-term benefits from traditional response efforts. More likely there are only non-beneficial results compared to natural attenuation. We conclude that the only longterm beneficial response method appears to be a combination of non-intrusive oil collection and booming techniques in heavily oiled, sheltered areas with closely monitored natural recovery in forests more lighly oiled. This should be paired with mitigation programs involving habitat creation either in unoiled areas or in the impact zone following the attenuation of oil and removal of debris from the deteriorating forests.

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

AbstractWhereas 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.

The Mangrove Ecosystem of the Ciénaga Grande de Santa Marta (Colombia): Observations on Regeneration and Trace Metals in Sediment

Alteration of water flows and consequent hypersalinization caused the death of nearly 70% of mangroves at the Ciénaga Grande de Santa Marta, Colombia. Efforts to rehabilitate the ecosystem have been made through the construction of freshwater channels. Mangrove recovery was observed along a freshwater channel and at a small lagoon behind the beach ridge. Factors identified in this study influencing mangrove regeneration are: salinity of surface water, duration and height of flooding, leaching property of soils, dispersal of propagules and presence of fertile trees. Besides mangrove regeneration, a notable extension of freshwater plants was observed in the channel. Trace metal concentrations in sediments from the Magdalena River and its area of influence were investigated before the complete opening of the first channel. A relative comparison indicated that the highest concentrations of Cd, Cu, Ni and Zn were above international recommended limits. However, metal concentrations found in sediments at Cları́n Channel did not affect the mangrove recovery.