Managing Rapid Sedimentation Through Mangrove Assisted Colonization as Carbon Sequestration Strategy in the Ajkwa Estuary, Papua, Indonesia

Abstract

The Ajkwa Estuary is in the Mimika Regency, Central Papua Province, Indonesia. As with many estuaries in the world, the Ajkwa Estuary is a productive ecosystem with a large variety of biodiversity that plays an important role as an ecosystem services provider, and the extensification of the system might lead to environmental challenges. The Ajkwa Estuary has experienced ecosystem changes due to the sedimentation of natural and mine-related sediments. This study investigates a novel approach to sedimentation management through the construction of Estuary Structures consisting of Geotube and Bamboo E-Groins to localize the sedimentation process at designated areas. This in turn provides areas for further mangrove colonization which acts to sequester carbon from the atmosphere. The results show that the construction of 2,700 meters of Geotube and 2,800 meters of bamboo-based E-groins structures have successfully increased sedimentation up to 1,5 m of elevation, creating areas suitable for the mangrove colonization process. Mangrove seedlings planted at new deposition areas around these estuary structures have shown a 90% survival rate. The aboveground carbon stock was calculated from a 500-ha mangrove-assisted colonization area and indicated that the vegetation could potentially sequester up to 20,919 atmospheric tons of CO2 equivalent to or equal to 5,716 tons of carbon stock. Based on the projection, a total of 5,000 hectares of new colonization area will be targeted for sediment deposition and mangrove colonization, which could contribute to 6,562,000 tons C equal to the absorption of 24,016,920 tons CO2 equivalent.

Keywords: carbon sequestration, estuary structure, mangrove, sedimentation, Ajkwa estuary