Main potential impacts on seagrasses from dredging and sand mining include physical removal and/o... more Main potential impacts on seagrasses from dredging and sand mining include physical removal and/or burial of vegetation and effects of increased turbidity and sedimentation. For seagrasses, the critical threshold for turbidity and sedimentation, as well as the duration that seagrasses can survive periods of high turbidity or excessive sedimentation vary greatly among species. Larger, slow-growing climax species with substantial carbohydrate reserves show greater resilience to such events than smaller opportunistic species, but the latter display much faster post-dredging recovery when water quality conditions return to their original state. A review of 45 case studies worldwide, accounting for a total loss of 21,023 ha of seagrass vegetation due to dredging, is indicative of the scale of the impact of dredging on seagrasses. In recent years, tighter control in the form of strict regulations, proper enforcement and monitoring, and mitigating measures together with proper impact assessment and development of new environmental dredging techniques help to prevent or minimize adverse impacts on seagrasses. Costs of such measures are difficult to estimate, but seem negligible in comparison with costs of seagrass restoration programmes, which are typically small-scale in approach and often have limited success. Copying of dredging criteria used in one geographic area to a dredging operation in another may in some cases lead to exaggerated limitations resulting in unnecessary costs and delays in dredging operations, or in other cases could prove damaging to seagrass ecosystems. Meaningful criteria to limit the extent and turbidity of dredging plumes and their effects will always require site-specific evaluations and should take into account the natural variability of local background turbidity.
We analyzed current best practices and recommendations used in the implementation of mangrove reh... more We analyzed current best practices and recommendations used in the implementation of mangrove rehabilitation and restoration (R/R) projects in the Atlantic-East Pacific (AEP) and the Indo-West Pacific biogeographic regions during the last 20 years. Comprehensive literature and World Wide Web searches were performed identifying 90 sites around the world where R/R actions have been implemented. For each site, we analyzed the sources of damage/impact and classified the origin as natural (siltation, erosion, the direct and indirect effect of tropical storms or tsunamis) or anthropogenic (pollution, land use policies, overharvesting, aquaculture, altered hydrology and hydroperiod). In most cases, the causes of damage were a complex mixture associated to erosion, hydrological impairment, deforestation, siltation, and land conversion for aquaculture and other land uses. The area extension of mangrove sites undergoing restoration or just afforestation ranged from few square meters to several thousand hectares. Numerous projects were implemented without an underlying science-based approach and were often ill-prepared and unsuccessful. Although there is no “one-size-fits-all” solution to restore or rehabilitate mangrove wetlands, published studies (particularly peer reviewed) provide useful insights into designing R/R projects with clearly defined and prioritized management objectives based on a diagnostic of the source of damage/deterioration. A critical step is to develop a decision tree that serves as a guide to optimize the use of available funding in the development, implementation, and monitoring of R/R protocols to set clear objectives, goals and deadlines. These steps should be part of a robust research agenda based on sound ecological theory and reliable monitoring practices, including the participation of local communities. Any monitoring and reporting program should address spatial and temporal replication that explicitly includes reference sites near the target restoration site. The results of each R/R project, whether successful or not, should be published, as they are critical sources of data and information for further development of mangrove R/R practices and methods within the community of restoration ecology science. We urge the continental level implementation of guidelines to advance international initiatives aimed to protect and conserve one the most productive and threatened coastal ecosystems in the world.
Keywords: Geographical distribution Land use change Monitoring Reference sites Rehabilitation Restoration
Main potential impacts on seagrasses from dredging and sand mining include physical removal and/o... more Main potential impacts on seagrasses from dredging and sand mining include physical removal and/or burial of vegetation and effects of increased turbidity and sedimentation. For seagrasses, the critical threshold for turbidity and sedimentation, as well as the duration that seagrasses can survive periods of high turbidity or excessive sedimentation vary greatly among species. Larger, slow-growing climax species with substantial carbohydrate reserves show greater resilience to such events than smaller opportunistic species, but the latter display much faster post-dredging recovery when water quality conditions return to their original state. A review of 45 case studies worldwide, accounting for a total loss of 21,023 ha of seagrass vegetation due to dredging, is indicative of the scale of the impact of dredging on seagrasses. In recent years, tighter control in the form of strict regulations, proper enforcement and monitoring, and mitigating measures together with proper impact assessment and development of new environmental dredging techniques help to prevent or minimize adverse impacts on seagrasses. Costs of such measures are difficult to estimate, but seem negligible in comparison with costs of seagrass restoration programmes, which are typically small-scale in approach and often have limited success. Copying of dredging criteria used in one geographic area to a dredging operation in another may in some cases lead to exaggerated limitations resulting in unnecessary costs and delays in dredging operations, or in other cases could prove damaging to seagrass ecosystems. Meaningful criteria to limit the extent and turbidity of dredging plumes and their effects will always require site-specific evaluations and should take into account the natural variability of local background turbidity.
We analyzed current best practices and recommendations used in the implementation of mangrove reh... more We analyzed current best practices and recommendations used in the implementation of mangrove rehabilitation and restoration (R/R) projects in the Atlantic-East Pacific (AEP) and the Indo-West Pacific biogeographic regions during the last 20 years. Comprehensive literature and World Wide Web searches were performed identifying 90 sites around the world where R/R actions have been implemented. For each site, we analyzed the sources of damage/impact and classified the origin as natural (siltation, erosion, the direct and indirect effect of tropical storms or tsunamis) or anthropogenic (pollution, land use policies, overharvesting, aquaculture, altered hydrology and hydroperiod). In most cases, the causes of damage were a complex mixture associated to erosion, hydrological impairment, deforestation, siltation, and land conversion for aquaculture and other land uses. The area extension of mangrove sites undergoing restoration or just afforestation ranged from few square meters to several thousand hectares. Numerous projects were implemented without an underlying science-based approach and were often ill-prepared and unsuccessful. Although there is no “one-size-fits-all” solution to restore or rehabilitate mangrove wetlands, published studies (particularly peer reviewed) provide useful insights into designing R/R projects with clearly defined and prioritized management objectives based on a diagnostic of the source of damage/deterioration. A critical step is to develop a decision tree that serves as a guide to optimize the use of available funding in the development, implementation, and monitoring of R/R protocols to set clear objectives, goals and deadlines. These steps should be part of a robust research agenda based on sound ecological theory and reliable monitoring practices, including the participation of local communities. Any monitoring and reporting program should address spatial and temporal replication that explicitly includes reference sites near the target restoration site. The results of each R/R project, whether successful or not, should be published, as they are critical sources of data and information for further development of mangrove R/R practices and methods within the community of restoration ecology science. We urge the continental level implementation of guidelines to advance international initiatives aimed to protect and conserve one the most productive and threatened coastal ecosystems in the world.
Keywords: Geographical distribution Land use change Monitoring Reference sites Rehabilitation Restoration
Uploads
Papers by Roy Lewis
Books by Roy Lewis
Keywords: Geographical distribution Land use change Monitoring Reference sites Rehabilitation Restoration
Keywords: Geographical distribution Land use change Monitoring Reference sites Rehabilitation Restoration