Have mangrove restoration projects worked? An in-depth study in Sri Lanka

This study investigated the effectiveness of mangrove planting initiatives in Sri Lanka. All the lagoons and estuaries in Sri Lanka were included in the study. We documented all agencies and locations, involved in mangrove planting efforts, along with the major drivers of these planting initiatives, their extents, and the possible causes of the success or failure of planting. An adapted three-step framework and a field survey consisting of vegetation and soil surveys and questionnaires were used to evaluate the objectives. We found that about 1,000–1,200 ha of mangroves, representing 23 project sites with 67 planting efforts, have been under restoration with the participation of several governmental and nongovernmental organizations. However, about 200–220 ha showed successful mangrove restoration. Nine out of 23 project sites (i.e. 36/67 planting efforts) showed no surviving plants. The level of survival of the restoration project sites ranged from 0 to 78% and only three sites, that is, Kalpitiya, Pambala, and Negombo, showed a level of survival higher than 50%. Survival rates were significantly correlated with post-care. Planting mangrove seedlings at the incorrect topography often entails inappropriate soil conditions for mangroves. Survival rates showed significant correlations with a range of soil parameters except soil pH. Disturbance and stress caused by cattle trampling, browsing, algal accumulation, and insect attacks, factors that may themselves relate to choosing sites with inappropriate topography and hydrology, were common to most sites. The findings are a stark illustration of the frequent mismatch between the purported aims of restoration initiatives and the realities on the ground.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The effects of salinity on growth and survival of mangrove seedlings changes with age

Six-wide ranging mangrove species, Rhizophora apiculata, R. mucronata, Avicennia marina, A. officinalis, Bruguiera gymnorrhiza, and B. sexangula, were selected to study the growth and survival of seedlings under three contrasting salinity treatments over a 30-week period: low (3-5psu), moderate (15-17psu) and high (33-36psu). Seedlings grown under high salinity exhibited significantly lower performance (p < 0.05) in survival rates, cumulative shoot height, mean growth rates, mean total leaf area, and mean dry weight, compared to those under low and moderate salinity regimes. Th e low salinity treatment provided the best conditions for initial establishment and growth of the seedlings of all species until 15-20 weeks of age. However, the same seedlings showed better performance under moderate salinity after 15-20 weeks of age (shift in optimal salinity), implying that adaptation to salt and physiological needs of mangrove seedlings varies with age. These results have practical implications of use in raising up mangrove nurse species for planting since it indicates that seedlings should get low salinity water until four to five months of age and then moderately saline water, in order to achieve maximum growth and survival

Stress-induced carbon starvation in Rhizophora mucronata Lam. seedlings under conditions of prolonged submergence and water deficiency: survive or succumb

The behaviour of carbohydrate metabolism in a plant, particularly its total starch content, total soluble sugar (TSS) content and their utilisation, is of great importance in coping with abiotic stress conditions. With this in mind, we studied total starch and TSS contents, survival, growth, biomass accumulation and stomatal conductance in Rhizophora mucronata under conditions of prolonged submergence and water stress for a period of 11 months. The experiment was designed in such a way as to include three replicates per each treatment level, about 1600 young mangrove plants being subjected to study in the process. Under conditions of prolonged submergence and high levels of water stress, a small number of mangrove plants survived and they were promptly exhausted due to higher starch utilisation rates (0.75–1.05% dry mass/month). Although TSS content was increased under these intense stress conditions, it was not matched by increased seedling growth or biomass production; instead, a significant reduction in growth (i.e. ∼78%) and dry matter content was observed in stressed seedlings as compared to young plants in the respective controls. It follows that the intense increase of TSS content might be due to the direct conversion of starch to soluble sugars in order to produce metabolic energy for tolerance mechanisms like osmoregulation and root anatomical adaptations under stress conditions. This indicates that more energy is allocated for plant maintenance than for growth and biomass production under stress conditions, which might be a good acclimatory strategy to rescue young mangrove plants at the early phase. However, stomatal closure under stress conditions may have caused restricted photosynthesis. Therefore, stress–induced starch degradation may upsurge, which in turn might lead in the long-run to carbon starvation, a condition lethal to mangrove seedlings.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Understanding the ethnobiological importance of mangroves to coastal communities: A case study from Southern and North-western Sri Lanka

Ethnobiological knowledge is an important part of people's capacity to manage, conserve, and improve the governance of mangrove ecosystems. This paper assesses the ethnobiological importance of mangroves to coastal communities adjacent to seven mangrove forests in Southern and North-western Sri Lanka. 197 households were interviewed, and respondents identified various mangrove ecosystem goods and services. Fruit juice produced from Sonneratia spp. and salads made with Acrostichum aureum L. young leaves constitutes valuable edible products in both regions. Rhizophora mucronata Lamk. and Lumnitzera racemosa Willd., were employed as alternative sources of fuel. Other uses of mangroves include wood for construction, chemical, and medicinal products. However, the usage extent was significantly higher in the Southern province (87.6%) compared to the North-western province (51%). Five indices were developed to understand the ethnobiological knowledge of respondents (Mangrove Use Index, Perception Index, Regulation Awareness Index, and Knowledge Index, Mangrove Dynamics Index). Except for the Mangrove Use Index, the rest of the indices were significantly different between the provinces. Communities with higher mangrove knowledge showed lesser usage. Respondents had negative attitudes towards the regulations that limit/did not allow the community to enter mangrove forests. Community participation, ethnobiological importance, and perspectives regarding how the community wants to manage mangrove forests should be taken into account to avoid conflicts in the future. Considering local perceptions and translating them into mangrove management regulations can be effective in guiding sustainable mangrove management in Sri Lanka as well as in other countries in the world

A social network analysis of mangrove management stakeholders in Sri Lanka's Northern Province

The sustainable management of complex social-ecological systems (SES) typically requires coordination and collaboration between various groups of stakeholders. Yet, research on collaborative stakeholder networks and their linkages with sustainable mangrove management strategies is lacking in Sri Lanka. This study presents a social network analysis (SNA) of mangrove management stakeholders and their perceptions of both existing and preferred collaborative relationships (or ties) between stakeholder groups, in the Northern Province of Sri Lanka. It further illustrates how SNA can be used to identify stakeholder collaboration and their potential role(s) in mangrove management. The perspectives of all key stakeholders have an impact on how mangroves need to be managed. Therefore, it is crucial to identify and meet with all key stakeholders in the early stages of management processes to understand their needs and constraints. Our findings indicate that the government departments mandated to conserve mangroves are not only formally appointed key stakeholders but are also perceived as central by others. Communication barriers, lack of awareness regarding the importance of mangroves, and shortages in staff and resources for conservation were major constraints to the existing mangrove management network. We highlight the potential of other stakeholders (i.e., non-mandated government stakeholders, non-governmental organizations (NGOs), and private organizations) in improving and influencing the social network in order to increase the diffusion of information. Despite existing resource extraction activities, private organizations were less represented in the mangrove management network of our study. After considering stakeholders’ expectations and requirements, we suggest the inclusion of a bridging organization such as an “Environment Network Unit” or the establishment of bridging entities in the universities and research institutes. We also recommend certain government organizations (i.e., Central Environmental Authority) to take up the role of bridging. This may help to facilitate the incorporation of relatively marginalized stakeholders in an effort to foster sustainable mangrove management in the Northern Province of Sri Lanka and beyond

Island-wide coastal vulnerability assessment of Sri Lanka reveals that sand dunes, planted trees and natural vegetation may play a role as potential barriers against ocean surges

Since the Indian Ocean tsunami on 26 December 2004, there have been continuous efforts to upgrade the (tsunami) early warning systems as well as their accessibility in local and regional places in South and Southeast Asia. Meanwhile, the protection offered by coastal vegetation like mangroves to the people, property and physical landscape was also recognized and prioritized by both public and private authorities at various governance levels. As more than 90% of the Sri Lankan coastline is vulnerable to water-related impacts and existing bioshields like mangroves are potentially able to protect less than one-third of it, if at all they are in good condition, an attempt was made to build knowledge on the other potential natural barriers along the coast. In this context, a ca. 2 km belt of the entire coast was digitized, classified and assessed for vulnerability in relation to the existing land-use/cover. First, a visually interpreted land-use/cover map comprising 16 classes was developed using Google Earth imagery (Landsat-5, 2003). Second, based on the Global Digital Elevation Model data from the ASTER satellite, the land-use/cover map was further re-classified for elevation demarcation into waterless, run-up and flooded areas. And finally, both vulnerable and less vulnerable areas were identified by taking into account the average wave heights that the 2004 tsunami reached in the country (North: 5.5 m, South: 7 m, East: 5 m and West: 3.75 m). Among the selected areas studied, Jaffna and Kaluvanchikudy-Komari are found to be vulnerable and, Trincomalee, Yala and Puttalam are less vulnerable. While vulnerability was largely associated with the conditions devoid of natural barriers, the less vulnerable areas had mangroves, Casuarina, dense vegetation and/or sand dunes as land cover, all of which might prove effective against ocean surges. However, these land cover types should never be considered as providing full protection against the type of threats that can be expected. As the present study provides only base-line information on island-wide vulnerability of areas to water-related impacts, further investigation and validation along similar research lines are needed to establish a blueprint for future preparedness

Island-wide coastal vulnerability assessment of Sri Lanka reveals sand dunes, planted trees and natural vegetation as potential barriers against ocean surges

info:eu-repo/semantics/publishe

Heavy metal pollution in selected upland tributaries of Sri Lanka: comprehension towards the localization of sources of pollution

This study aimed to assess the heavy metal (HM) profile of the main upland tributaries of three major rivers, the Mahaweli, the Deduru and the Gin Rivers, which are commonly used for urban water supply in Sri Lanka. The HM profiles of arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) were investigated by ICP-MS. Land-use classification was performed to locate the main sources of pollution. Mean pH, TDS and conductivity showed significant inter-site mean differences (p, 0.001). The mean contents of the HMs, considering all rivers, were observed in the order [Hg] .[As] .[Pb] .[Cd] at the sources and [As] .[Hg] .[Pb] .[Cd] at the river mouths. Particularly, in the Mahaweli River, the mean As content was 0.08 + 0.05 μg·L-1 and showed an increasing trend from the source to the river mouth. In the Deduru River, the mean Hg content was 0.14 + 0.15 μg·L-1, and of all rivers studied, the highest content of 0.50 + 0.17 μg·L-1 was recorded. The Gin River showed significant inter-site mean differences (p, 0.05) in [Pb], [As] and [Hg]. In all rivers studied, [As] was significantly higher in water samples collected near agricultural lands and urban areas as compared with the other land-use/cover types, which was further proved by a significant positive correlation (coefficient ¼ 0.479, p ¼ 0.0325). We, therefore, emphasized that HM pollution is more likely due to anthropogenic activities in the upper catchment with less lithogenic contamination. However, national water quality management should be further strengthened and new policy enforcement is emphasized.SCOPUS: ar.jinfo:eu-repo/semantics/publishe