Economic valuation from direct use of mangrove forest restoration in Balikpapan Bay, East Kalimantan, Indonesia

Background: The mangrove forests in Balikpapan Bay, Indonesia, have been used as a source of livelihood for local community more than 150 years. Since the natural products of the mangrove forest, such as wood and seafood, are not able to meet the economic needs of the local community, some areas have been converted into brackish water ponds with traditional aquaculture systems. The growth of brackish water ponds over the last five decades has been identified as the main cause of ecosystem destruction. However, the mangrove ecosystem has been restored naturally through tidal action and seeds falling from mangrove trees. Methods: This study focused on the mangrove tree species Rhizophora apiculata, with ages ranging from 3 to 40 years. Initially, the study site (area, 1 ha) was plotted. The study sample size included 30% of the local population, chosen by systematic random sampling. The data collection was undertaken as follows: 1) measurement of the diameter and height of mangrove trees; 2) observation of local fish auctions; and 3) interviewing of fishers and local communities regarding the direct use of the natural products of the mangrove ecosystem. Results: It is suggested that the total income from wood production is IDR 742,425,000 year (-1) or US $0.933 person (-1) day (-1). Furthermore, the total income from fishing is IDR 1,080,353,280 year (-1) or US $1.43 person (-1) day (-1). Pre-thinning income level for wood harvesting is still low. The income difference between wood production and fishing resulted in the rate of overfishing reaching 45.5%. The highest observed wood production was reached at the age of 25 years, and the highest value of mean annual increment (MAI) is 5.39 m (3 )ha (-1 )at the age of 40 years. Conclusions: This study showed that tree thinning, ranging from 90 to 350 trees ha (-1), can increase the value of MAI by around 24.5%.