Valuation of Mangrove Ecosystems along the Coast of the Mekong Delta in Vietnam - an approach combining socio-economic and remote sensing methods

Kurzfassung

Mangrove ecosystem is among the most productive and valuable eosystems in the world.The services provided by mangrove ecosystems to human well-being are well acknowledged in literature. Mangrove forests provide not only direct use values such as timber materials and fisheries resources but also indirect use values, for instance coastal protection, carbon sequestration as well as biodiversity. Although mangrove forests play an important role in providing goods and services to humans in both direct and indirect ways, they are declining at alarming rates. Overexploitation of mangrove for timber, urban development, increase population in coastal areas, and especially conversion to aquaculture are the major threats to mangrove forests worldwide. Over the last two decades, many studies on the valuation of mangrove ecosystems using different valuation approaches have been carried out in order to increase the awareness of decision makers to mangrove ecosystems. This dissertation investigates a new approach for quantifying the value of mangrove ecosystem services using remote sensing and household socio-economic data. Specifically, the method differentiates mangrove cover fractions in a mangrove-aquaculture integrated farming system in Ca Mau Province, Mekong Delta using an object-based approach. Ca Mau Province serves as an interesting case study as it has special conditions. First, it is the Province that hosts one of the largest mangrove forest areas in the Mekong Delta. Second, mangrove forests in this Province have been declining rapidly due to expansion of shrimp farming. Last, it is the Province that has special characteristics of the integrated mangrove-quaculture farming system, where mangroves are planted in a shrimp pond with different mangroves densities. This dissertation reviews a comprehensive overview of methods applied for the valuation of mangrove ecosystem services undertaken for the last decades. The main findings of this research include the following: 1) a need for site/landscape-specific valuation of mangrove ecosystem due to the socio-economic context as well as inconsistency in the value-transfer approach; monetary valuation should be used to increase awareness of the importance of mangrove ecosystems to decision akers/local communities. 2) developed an object-based approach for estimating the percentage of mangroves in mixed mangrove-aquaculture farming systems. This approach is a first attempt to quantitatively estimate mangrove percentages within the special mangrove-aquaculture farming system in the Mekong Delta of Vietnam. The method comprises multi-resolution segmentation and classification of SPOT5 data using a decision tree approach as well as local knowledge from the region of interest. The results demonstrate that the predominantly mono-cultivation areas, i.e., above 70% or below 30% mangrove forests, were detected with high accuracies compared with existing approaches, 3) the valuation of mangrove ecosystem services using combined approach of remote sensing and socio-economic household survey data. The total estimated value was US$ 600 million/year for 187,533 ha with the mean value was US$3,000/ha/year, which significantly greater than gross domestic product (GDP) of the Province (US$ 1.25 million in 2010). The results demonstrate advancements in remote sensing techniques in combination with household survey data in quantifying the value of mangrove ecosystems. However, future challenges remain before this approach can be applied in monitoring the extent of mangrove and estimating the total economic value of the mangrove ecosystem. Based on these results, future research should focus on the integration of additional geodata, such as cadastral maps in the segmentation process, or emerging remote sensing technologies such as LiDAR or hyper-spectral data to characterize mangrove species and structure. Primary research on the valuation of recreation, water filtration or biodiversity needs to be done in order to estimate the total economic value of mangrove ecosystems.