Welfare impact of climate change on capture fisheries in Vietnam

From Eq (12), we have: PS1 PS0 ¼ að1þεSÞ εS εD bð 1 εDÞ εS εD > 1 $ a > b 1þεD εS εD ð22Þ Eq (22) is correct since a > 1 > b 1þεD εS εD . Therefore, when demand increases, producer surplus increases. We recall Eq (10): CS1 CS0 ¼ a 1 P1þεD 1 P1þεD 0 Pmax1þεD P1þεD 0 � � ð10Þ Eq (10) is increasing in a. When a = 1, CS1 CS0 < 1. When a is large enough, then CS1 CS0 > 1, which means that consumers start to gain if their demand surpasses a certain threshold. Table 5 summarises the dynamics of producer and consumer welfares, with respect to an increase in a while b keeps constant from the previous results. Discussions and conclusions The research results confirm the adverse impact of climate change on catch yield. Temperature rise is the primary cause of the declining production since it triggers tropical fish to migrate to more comfortable areas and the rest to reduce their sizes and stocks [4, 7, 54, 56, 58, 59]. The impact of temperature increases with time and severity of climate change scenarios. The cap- ture yield will reduce 35% from now to mid-century under the RCP4.5. This result is close to Cheung et al.’s (2010) projection that the catch potential in the Pacific Ocean in 10N–30N will decrease up to 30% until 2055 under the B1 (equivalent to RCP4.5) scenario. The worst sce- nario predicts that there will be no capture by the end of the century. This forecast is not sur- prising, as it has recently been almost no river capture in Vietnam. The negative impacts of sea surface temperature, rainfall, typhoons, and wind speed on

catch yields are also found in various literature in Vietnam [61] and other places [17, 27, 42, 47, 62–64, 71, 73, 84]. For instance, Garza-Gil, Torralba-Cano [84] report a 10% rise in tem- perature leading to a 1.4% annual decrease in the European sardine fishery’s profit. The total Taiwan trout population is likely to decline from 1612 to 974 if precipitation increases by 0.6 mm per day and the temperature increases by 0.9˚C [73]. Meynecke, Grubert [64] indicate that a high SOI value enhances the productivity of giant mud crab (Scylla Serrata) catches in Northern Australia. Alnafissa, Kotb [47] realize an increase of 10% in the wind speed heading to a decrease of 6.8% in fish production in Saudi Arabia. The welfare impacts of climate change on producers and consumers depend significantly on the change in wild fish demand. If the demand curve remains unchanged, then the drop in supply induces fishery price increase, creating tremendous loss to consumers, from 7 to 9 billion USD by 2035 and from 10 to 18 billion USD in 2065 (PPP, 2018). If the demand decreases, mainly due to the substitution effect of the aquaculture expansion, consumers also suffer from loss. If the demand increases, Table 5. The dynamics of producer and consumer welfares under climate change. a < b < 1 a = b < 1 b < a < 1 a = 1 a > 1 Consumer surplus – – – – – then + Producer surplus – – – then + + + Social surplus – – – – – then + https://doi.org/10.1371/journal.pone.0264997.t005 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 15 / 20