Methods
Our interdisciplinary team comprised researchers across career stages and from different environmental and social disciplines. We collaborated over a series of workshops and meetings in 2018 and 2019 that were organised as part of the Future Seas project (https://futureseas2030.org/). This project aimed at developing mobilising narratives across key challenges for the future of our ocean (one of which is developing the offshore Blue Economy) and involved more than 100 scientists. Working in such extended group allowed for inputs from Future Seas participants beyond those directly involved in this paper.
We followed the methods tested and agreed during the first Future Seas workshop and common to all challenges (Nash et al. 2020a). We developed two plausible futures in 2030 for the offshore Blue Economy and defined a pathway to action. The first of these futures is the anticipated business as usual based on current trajectories (Plankque et al. 2019) and informed by published evidence. The second is an optimistic but technically achievable more sustainable future aligned as much as possible with SDGs and informed by existing and emerging knowledge. We used a predictive approach to develop the business as usual scenario and a normative approach to build the more sustainable scenario (Börjeson et al. 2006). A range of assumptions negotiated among Future Seas participants and common to all challenges constrain the futures. Example of these assumptions are that population and resource use will continue to increase to 2030, and that the globe is locked into climate change of at least 1.5°C by 2030. A full list of assumptions can be found in Nash et al. (2020a).
1. Scenario development
As a first step towards scenarios development, we identified key drivers that society can influence and that will impact the offshore Blue Economy over the Oceans Decade (by 2030; UNESCO 2019) (Table 1). To do so, we brainstormed drivers of change in six categories: political, economic, social, technological, legal, and environmental (PESTLE analysis). Following brainstorming, we revised our detailed drivers and grouped them into broader categories. Last, we mapped these categorised drivers on a graph of low-to-high-influence versus low-to-high-impact axes, and we selected those that society can most influence and that are characterised by a high degree of impact on the offshore Blue Economy.
Once satisfied with our selection, we determined shifts in the intensity and direction of drivers that will lead to the different futures. This resulted in a table of key drivers and their behaviour in the context of the business as usual and the more sustainable future. This table became the starting point for developing the narrative around the alternative futures (Table 1). To guide the definition of the business as usual and the more sustainable future, we also looked to the SDGs. We identified which of the globally important goals the offshore Blue Economy has the greatest potential to influence (Fig. 2 and Table 1) and we discussed to what extent they might be achieved in each future (Table S1). We gave less consideration to SDGs that are more relevant to other papers of this special issue (e.g. Farmery et al. 2020 focusing on SDG Zero Hunger, Alexander et al. 2020 considering equity as per SDG 10, and Trebilco et al. 2020 discussing climate actions).
We acknowledge that the evolution of the COVID-19 pandemic is causing major changes to economies and socioecological systems at the global scale. It has changed growth rates and has seen calls for a redirection during recovery, thus potentially pulled society away from the business as usual path as outlined here and based on evidence prior to the pandemic. Free from any defined trajectory, society has a choice to make. It can return to the business as usual trajectory prior to COVID-19 in the next few years; or it can consider the current disruption to the global ocean, environment and society because of COVID-19 as an opportunity to switch to a different trajectory in the coming decade (as discussed in Pecl et al. 2020). The sustainable future presented here is one option for such a shift.
2.  Pathway towards a more sustainable future
We used a backcasting technique to identify tangible actions that support society in moving towards the more sustainable future. Backcasting is commonly used to define pathways that require knowledge of the end-point to determine the measures needed to reach that point (Robinson 1990). As a first step and guided by our vision of a more sustainable future, we brainstormed actions required to achieve this future and we identified who among the actors of the offshore Blue Economy (civil society, government, non-government and international organisation, industry, academia) should take each action. Next, we asked how long it would take for each action to be implemented and we placed each action on a 2021-2030 timeline, coinciding with the UN Decade of Ocean Science. Last, we identified the risks of taking actions. The aim of this last step was to promote a deep consideration of all aspects of an action (gains and losses), and to isolate actions that might lead to unintended outcomes and path dependency or that require additional precursors or enabling actions.
Both the process of scenario development and that of identification of tangible actions were iterative and involved repeated revisions of constituent steps and components (drivers, characteristics and descriptions of futures, and actions).