Empowerment of Abandoned Ponds for Sustainable Mangrove Rehabilitation Activities in Percut Sei Tuan, Deli Serdang, Indonesia

Mangrove ecosystems provide important functions for ecosystem service. However, the degradation of mangrove forests, especially conversion to aquaculture ponds is a driver for deforestation. Therefore, this study aimed to analyze the mangrove vegetation and duration of inundation in ponds before and after rehabilitation activities were conducted on abandoned ponds. In this analysis, we used the census method to collect structural data, the Important Value Index (IVI), composition and structure, and the diversity index. To determine the duration of inundation at the observation sites in a pond in Tanjung Rejo, Percut Sei Tuan village, we deployed one water logger and two Mini Buoys at ponds. At the observation site, eight pure mangrove species have been founded, namely Avicennia alba, A. marina, Bruguiera gymnorrhiza, Excoecaria agallocha, Rhizophora apiculata, R. mucronata, R. stylosa, and Nypa fruticans. The main species was A. marina which is a total of 756 idv/ha at the seedling stage 52.81 idv/ha at the sapling stage, and 268.09 idv/ha at the tree level. The highest IVI has founded in seedlings, saplings, and trees at A. marina, which was 99.30%. 80.41% and 94.49%, respectively. Rehabilitated Avicennia spp that grew only 2.4% from 2000 seedlings. The low growth of seedlings was influenced by the pond condition which was always in a state of flooding. The current study provides important information that in carrying out planting or rehabilitation activities it is necessary to determine which inundation rotation should be a priority considered

Dynamic System for Silvofishery Pond Feasibility in North Sumatera, Indonesia

Silvofishery is the planting of mangroves in pond area. The commodities selected for silvofishery ponds include tiger shrimp, milkfish, and mangrove crab. The purpose of this research was to find the best silvofishery system based on the average net present value (NPV) using a dynamic model simulation and provide information about the effect of price changes or production of selected commodities on silvofishery. The results of this research showed that tiger shrimp and mud crab are the best and most feasible combinations for silvofishery, having an average NPV of $755.71/ha/year. Meanwhile, silvofishery using tiger shrimp has an average NPV of$332.28/ha/year, and the silvofishery combination of milkfish and tiger shrimp has an average NPV of $-216.45/ha/year. The effect of price increases the variable cost price by 63.3%, which indicates that the silvofishery combination of tiger shrimp and mud crab is still feasible to run. The decline in the selling price of the commodities of tiger shrimps and mud crab by 70% and 50%, respectively, makes this combination still feasible to operate. On the other hand, the surrounding community’s level of consumption greatly affects the level of sale of the silvofishery commodity. Environmental management must also be practiced as best as possible to maintain the functioning of the environment around the ponds to avoid major losses, and periodic maintenance must be done by managers to achieve the production targets. The present study suggested that pond farmers must be wise in making decisions to implement the appropriate combination of silvofishery

Macrozoobenthic community assemblage as key indicator for mangrove restoration success in North Sumatra and Aceh, Indonesia

The recognition of the high value of mangrove forests and the wide array of ecosystem services they provide has motivated investment in worldwide restoration efforts. However, current metrics of functional restoration (other than seedling survival rates and plant community composition) are often not readily available for local community managers, highlighting an urgency to identify easy-to-measure indicators to assess the functionality of restored mangroves. The macrozoobenthic community, could be such practical indicator, as macrozoobenthic communities are sensitive to changes in their environment, and can be easily surveyed within local managing programs. Focusing on three main mangrove management conditions (natural, planted and naturally regenerated) in North Sumatra and the province of Aceh, Indonesia, we compared vegetation and macrozoobenthic community diversity indices and identified environmental variables that best describe the forest management conditions and their associated macrozoobenthic community assemblage. Results showed that community assemblage, rather than macrozoobenthic diversity index, was associated with management conditions. The highest dissimilarity in macrozoobenthic community assemblages occurred between planted vs. natural mangroves, with non-significant dissimilarity between natural and naturally regenerated mangroves. The Lined Nerite gastropod (Nerita balteata) was identified as an indicator of natural mangroves, and the invasive Giant African snail (Achatina fulica), was abundant in mangrove plantations, but also in natural mangroves bordering harbors, oil palm plantations and aquaculture ponds, suggesting associated anthropogenic pressures. This study showed that the macrozoobenthic community can be used as restoration indicator and, could serve as a baseline to empower monitoring activities and community-based adaptive management practices to improve the outcomes of restoration efforts

Evaluation of Plant Growth and Potential of Carbon Storage in the Restored Mangrove of an Abandoned Pond in Lubuk Kertang, North Sumatra, Indonesia

Mangrove forest in Lubuk Kertang Village, West Brandan sub-district has been converted around 20 ha annually (1996–2016) into various non-forest land use. Rehabilitation can be a solution to restore the condition of the ecosystem so that it can resume its ecological and economic functions. This paper discusses the evaluation of mangrove rehabilitation carried out by planting 6000 propagules in December 2015 and 5000 seedlings in May 2016 with Rhizophora apiculata species in abandoned ponds. Monitoring was carried out every 6 months from 2016 to 2022. In the restored area, 11 true mangrove species and 3 associated mangrove species were found. The percentage of plants that survived after seven years was 69.42% for planting using propagules and 86.38% for planting with seedlings. The total biomass carbon stocks stored by 7-year-old plants using propagules was 51.18 Mg ha−1, while the carbon stored by planting using seedlings was 56.79 Mg ha−1. Soil carbon stocks at the planted site with propagules were 506.89 ± 250.74 MgC ha−1, and at the planted site with seedlings were 461.85 ± 102.23 MgC ha−1. The total ecosystem carbon stocks (including aboveground carbon) in the planted site using propagules were 558.07 MgC ha−1, while planting using seedlings were 518.64 MgC ha−1. The dataset and findings on the carbon storage evaluation of mangrove rehabilitation will be useful for blue carbon research community and policymakers in the context of the climate change mitigation strategy for Indonesia