Welfare impact of climate change on capture fisheries in Vietnam

Change in social surplus: DSS ¼ DCS þ DPS ð13Þ Demand function About 85% of Vietnam’s total catches are for domestic use, and the rest, 15%, is for export [2]. It is acceptable to assume that the own-price elasticity of total demand for fisheries equals its domestic one. Total market demand, by economic principles, is the sum of individual house- hold demands. Therefore, we assume that the individual households and the total market for wild fish bear identical demand elasticities. We recall the demand function from Eq (2): ln QD ¼ ln AD þ εD ln P ð2Þ In microeconomics, the consumer’s Marshallian demand depends on its price, consumer income, and prices of substitutes. Household demand also varies on household size, number of children, and other factors such as region, urban/rural location, occupation, employment, education, age, race, religion, crop, and availability of fishery shops [78]. Data from Vietnam Household Living Standards Survey (VHLSS) in 2018 [79] are exploited to develop the household demand function. The survey covered 9,399 households, representative at national, regional, urban, rural, and provincial levels. The survey collected information on household’s income, expenditure and other issues during four periods, each period in one quarter from the first to the fourth quarter in 2018 through face-to-face inter- views conducted by interviewers with household heads and household members. After omit- ting missing values, the final sample for the demand function regression model has 8,288 observations.

The dependent variable is fishery consumption quantity in 12 months in logarithm form, irrespective of capture or culture. In Vietnam, substitutes for fishery products are often pork and chicken. Therefore, the fishery demand function has the following form: lnQfish ¼ b0 þ b1 lnPfish þ b2 lnY þ b3 lnPpork þ b4 lnPchicken þ Pn i¼5biXi þ εt ð14Þ whereas Qfish is household fish intake in 12 months (kg); Pfish is fish price paid by household (thousand dongs per kg); Y is the household income per capita (thousand dongs); Ppork and Pchicken are prices of substitutes, which are pork and chicken (thousand dongs per kg); Xi is a set of other independent variables. Following Cheng and Capps [78], Xi include dum- mies for five geographical regions: Red River Delta, North Central and Coastal Central, Cen- tral Highland, Southeast, and Mekong Delta (Northwest region is the base category); coastal provinces, number of household members, and characteristics of household head such as gen- der, age, education, marital status, and occupation (self-employed in agriculture, self- employed in non-agriculture or service sector; non-self-employment is the base category); βk are coefficients, in which β1 is the own-price elasticity, and εt is the error term. Results Impact of climate change on potential catches The long-run form of the ARDL model indicates the long-run impact of climate change on catch fisheries. The results are presented in Table 2. PLOS ONE Welfare impact of climate change on capture fisheries in Vietnam

PLOS ONE | https://doi.org/10.1371/journal.pone.0264997 April 25, 2022 7 / 20