B. The Economic Valuation ApproachAs discussed in the introduction,the totaleconomic value of the remaining 400 ha ofmangroves to the local community may com-prise many diverse benefits. However,due tolimited data,the case study of the Tha PoVillage was able to estimate only the value ofthree key economic benefits: the value to thevillagers of their direct use of wood and non-timber products from the forest and the eco-logical values of the mangrove area in termsof off-shore fishery linkages and coastlineprotection. These values of the mangrove for-est were estimated to obtain the net benefitsof protecting the remaining mangrove area,which in turn are compared to the returns ofthe alternative use of the mangroves,which inthis case is conversion to shrimp farming. Therest of this section discusses the economicvaluation of the three key benefits to local vil-lagers of protecting the remaining mangrovearea. Section III contains the estimation ofthe returns from converting the mangroves toshrimp farming.TABLE 1Net Income from the Major Mangrove Products Collected by Tha Po HouseholdsAverage AnnualReturns per Total Annual NetNumber of Households Household Income of VillageProducts Engaged in Collection (US $) (US $)Fish 11 385 4235Shrimp 3 2079 6237Crab 13 1279 16627Molluscs 6 17 102Honey 88a55 4840Wood for fishing gear 44a9 396aEstimated from survey sample.C. Local Direct Use Value ofForest ResourcesThe direct use value of mangroveresources was assumed to be equivalent tothe net income generated from the forests interms of various wood and nonwood prod-ucts. If the extracted products were sold,market prices were used to calculate the netincome generated (gross income is minus thecost of extraction). If the products were usedonly for subsistence,the gross income wasestimated based on surrogate prices,that is,the market prices of the closest substitute.To estimate these local use values,twofield surveys were conducted. The first wasa detailed household survey that took placein February 1996 to obtain data on the fre-quency and quantity of the different prod-ucts collected from the mangroves,as wellas the labor input used in collecting theseproducts. The follow-up survey in June 1996used in-depth household interviews to acquiremore specific data. The surveys revealed thatthe major products collected by the house-holds were various fishery products,honey,and wood for fishing gear. The second sur-vey also revealed that the villagers collectedfuel wood,although most of the intervieweesstated that the quality of the wood found inthe remaining forest area was not suitablefor fuel wood,so they actually collected onlysmall amounts. Moreover,as the trees are rel-atively small,the villagers could not use themfor timber,except for repairing fishing gear.