Potential socioeconomic impacts from ocean acidification and climate change effects on Atlantic Canadian fisheries

risk assessments addressing ocean acidification’s impacts on fisheries [17], wherein risk is defined as the intersection of a hazard, exposure to the hazard, and vulnerability to the hazard (following the IPCC Working Group II report: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation—Chapter 2: Determinants of Risk: Expo- sure and Vulnerability. [18]). Vulnerability in turn encompassed two sub-components: sensi- tivity and adaptive capacity. This assessment follows similar definitions with the potential impact being defined as the combination of social vulnerability and biophysical exposure to the hazard of climate change and ocean acidification. The potential impact is not an absolute measurement, rather it is a metric for a relative comparison of how susceptible the provinces are to changing conditions. In the framework developed for Atlantic Canada, the exposure component represented the modelled OA and climate change-driven effects on the fisheries as determined through analy- sis of DBEM outputs. The sensitivity and adaptive capacity terms were used to describe the social factors that may obstruct or fortify communities’ responses to changes in fisheries. In total, the impact index was informed by six separate indicators: one for exposure, two for sen- sitivity, and three for adaptive capacity (Fig 4). Within each individual component of the framework, the sub-components or indicators were equally weighted. This weighting inher- ently implies that the indicators contribute equally to potential impacts in the region. In reality,

this is unlikely to be the case, however without strong support for preferential weights, equal weighting was selected as the most straightforward and neutral system [42,43] (Fig 4). Although a cumulative impact index was constructed, the biophysical and social factors should be considered as representing two distinct aspects of potential impact [14,18]. The combined index represents where these two dimensions overlap to have the highest effect. The biophysical indicator (i.e., exposure) represents where the most prominent changes in the resource will occur; and the social indicators (i.e., vulnerability) highlight where the expected changes are likely to have the highest impact given the current socioeconomic setting. Two of the provinces, NB and NS, border two separate DFO management areas (the Gulf and the Maritime management areas; Fig 2). For the purposes of this analysis, these two prov- inces were sub-divided into gulf (NB-gulf; NS-gulf) and maritime (NB-mar; NS-mar) provin- cial sub-sections. However, both sub-sections of the respective provinces rely on the same social data because these data were not available at a resolution that would have allowed sepa- rate treatments within the provinces. The sub-sections were exposed separately to potential changes in both relevant DFO management areas. Exposure indicator construction. The most significant divergence from previous risk/ vulnerability assessments of potential impacts from OA was the inclusion of a biophysical model to inform the exposure and hazard components of the framework simultaneously. Past

assessments have used an expected change in ocean chemistry to represent OA (the hazard) and used this in concert with the importance of OA susceptible fisheries (the exposure) to link the OA phenomenon with fisheries [11,14,15,17]. In this assessment, the biophysical model directly applied the expected climate change impact (including OA) onto the relevant fisheries. This allowed the change in fisheries landings to be explicitly incorporated into the framework. Thus the hazard and exposure terms were essentially incorporated into a single term (collec- tively referred to as ‘exposure’ throughout this assessment). A single indicator to account for all of the assessed species was constructed. To reflect the very different current economic contributions of individual species to total landed value, the proportion of the total shellfish value derived from each species was calculated and multiplied by its DBEM-predicted relative change for each management area. These value-scaled changes were summed across all assessed species (Eq 2). This was repeated separately for 2050 and 2090 and both RCP climate scenarios to obtain four exposure indicator scores per OA and climate change impacts on Atlantic Canadian fisheries PLOS ONE | https://doi.org/10.1371/journal.pone.0226544 January 10, 2020 7 / 29