Realistic fisheries management reforms could mitigate the impacts of climate change in most countries

Introduction Marine fisheries provide a vital source of food for over half the world’s population and support the livelihoods of over 56 million people globally [1]. However, the ability for marine fisheries to provide these services is threatened by climate change [2], compromising the contribution of the oceans to sustainable development goals [3]. Ocean warming has already reduced the productivity of many fisheries around the globe, with some regions having experienced up to 35% declines in maximum sustainable yield [4]. An ensemble of marine ecosystem models forecasts continued decreases in marine animal biomass of 4.8% to 17.2% by 2100 under low- to high-end emissions scenarios, respectively [5]. In general, productivity is predicted to decrease in tropical and temperate regions and increase towards the poles [5], as marine organisms shift distributions to maintain their thermal niches [6–8]. These regional shifts in productivity, range, and fishing opportunity will result in regional discrepancies in food and profits from fisheries [9]. Under current policies, these effects will be unevenly distributed with tropical developing countries and small island developing states exhibiting the greatest vulnerability to the impacts of climate change on fisheries [10–12]. The response of fishers and managers to these changes could either exacerbate or mitigate the impacts of climate change on human society and must be considered in forecasts of cli- mate impacts on marine fisheries [13,14]. For example, a failure to reduce harvest rates in

response to decreasing productivity could increase the risk of overfishing [15], which could subsequently reduce the resilience of stocks to climate change [4] and result in reduced long-term yields [16]. Similarly, a failure to establish transboundary institutions for manag- ing stocks shifting distributions across territorial boundaries could result in the degradation of management and stock health, catch, and profits [17,18]. In both cases, failing to adapt fisheries management to climate change would exacerbate the impacts of the underlying shifts in productivity on human society. On the other hand, jointly reforming fisheries man- agement and adapting it to account for these climate-driven shifts in productivity and distri- bution could reduce, or even reverse, the negative impacts of climate change on communities dependent on fishing [13,19]. Gaines et al. [19] provided a critical step towards understanding the opportunities for fish- eries reforms to mitigate the impacts of climate change at a global-level. They showed, at a global scale, that business-as-usual fisheries management would exacerbate the negative impacts of climate change, but that climate-adaptive fisheries reforms would maintain global fisheries health, harvest, and profits into the future under all but the most severe emissions scenario evaluated (RCP 8.5). However, the effectiveness and feasibility of these reforms is likely to vary regionally, with higher capacity, poleward countries gaining productivity and

lower capacity, tropical countries losing productivity. Furthermore, the benefits documented by Gaines et al. [19] are likely optimistic, as they assume real-time adaptations to shifting pro- ductivity. This degree of adaptation potential is unlikely even in the United States where stock assessments are conducted every two to five years [20] and do not frequently include environ- mental or ecosystem information [21]. Thus, a critical next step in understanding the potential for fisheries reform to mitigate the impacts of climate change on human livelihoods is to exam- ine the performance of more realistic productivity adaptations at the country-level. Here, we use the Gaines et al. [19] climate-linked bioeconomic model to evaluate the impacts of climate change and management reform on fisheries representing 156 countries, 779 marine fish and invertebrate species, and approximately 58.2% of reported global catch (45.6 of 78.4 mt in 2012; [1]). The evaluated management scenarios address shifting productiv- ity and distributions along a gradient from no adaptation (a.k.a., business-as-usual manage- ment) to full adaptation, including scenarios with realistic intervals between management PLOS ONE Realistic fisheries management reforms could mitigate the impacts of climate change in most countries PLOS ONE | https://doi.org/10.1371/journal.pone.0224347 March 5, 2020 2 / 21 analysis, decision to publish, or preparation of the manuscript. Competing interests: C.C. is a trustee for Environmental Defense Fund and Global Fishing Watch, is senior fellow at the Property and

Environment Research Center, and is a research associate with the National Bureau of Economic Research. S.D.G. is a trustee of the National Marine Sanctuary Foundation, Rare, Resources Legacy Fund, and COMPASS. This does not alter our adherence to PLOS ONE policies on sharing data and materials. All other authors declare that they have no competing interests.