One of the most pronounced effects of climate change on the world's oceans is the (generally) poleward movement of species and fishery stocks in response to increasing water temperatures. In some regions, such redistributions are already causing dramatic shifts in marine socioecological systems, profoundly altering ecosystem structure and function, challenging domestic and international fisheries, and impacting on human communities. Such effects are expected to become increasingly widespread as waters continue to warm and species ranges continue to shift. Actions taken over the coming decade (2021-2030) can help us adapt to species redistributions and minimise negative impacts on ecosystems and human communities, achieving a more sustainable future in the face of ecosystem change. We describe key drivers related to climate-driven species redistributions that are likely to have a high impact and influence on whether a sustainable future is achievable by 2030. We posit two different futures-a 'business as usual' future and a technically achievable and more sustainable future, aligned with the Sustainable Development Goals. We then identify concrete actions that provide a

Coastal Indigenous and Traditional communities are starting to see changes to their lives from climate change, whether this is from species range changes or displacement from land changes. For many of these communities, the ability to adequately adapt to these changes is limited by the governance structures they are required to live within, which differ from their customary practices and culture. In November 2019, a group of Indigenous and Traditional Peoples, attended the Future Seas 2030 workshop and discussed the consequences of climate change, the biggest barriers for their communities, and barriers for using traditional knowledge in order to contribute towards a more sustainable future that in the end will benefit all of earth’s people. The aim of this workshop was to highlight and give a voice to the various backgrounds and real-life situations impacting on some of the world’s Indigenous and Traditional communities whose connection with the oceans and coasts have been disrupted. This paper presents these issues of oppression, colonisation, language and agency, making it difficult for these groups to contribute to the current management of oceans and coasts, and asks scientists and practitioners in this space to be allies and enable the needed shift to earth’s guardians taking a leading role in nurturing her for our future.

We would like to acknowledge the tireless work of Halfdan Pedersen who worked as our translator with our Greenlandic colleague Nuunoq. Without him the input from Attu would not have been able to be included.

Proactive and coordinated action to mitigate and adapt to climate change will be essential for achieving the healthy, resilient, safe, sustainably harvested and biodiverse ocean that the UN Decade of Ocean Science and sustainable development goals (SDGs) seek. Ocean-based mitigation actions could contribute 12% of the emissions reductions required by 2030 to keep warming to less than 1.5 ºC but, because substantial warming is already locked in, extensive adaptation action is also needed. Here, as part of the Future Seas project, we use a “foresighting/hindcasting” technique to describe two scenarios for 2030 in the context of climate change mitigation and adaptation for ocean systems. The “business-as-usual” future is expected if current trends continue, while an alternative future could be realised if society were to effectively use available data and knowledge to push as far as possible towards achieving the UN SDGs. We identify three drivers that differentiate between these alternative futures: (i) appetite for climate action, (ii) handling extreme events, and (iii) climate interventions. Actions that could navigate towards the optimistic, sustainable and technically achievable future include: proactive creation and enhancement of economic incentives for mitigation and adaptation; supporting the proliferation of local initiatives to spur a global transformation; enhancing proactive coastal adaptation management; investing in research to support adaptation to emerging risks; deploying marine-based renewable energy; deploying marine-based negative emissions technologies; developing and assessing solar radiation management approaches; and deploying appropriate solar radiation management approaches to help safeguard critical ecosystems. Supplementary Information The online version contains supplementary material available at 10.1007/s11160-021-09678-4.

Proactive and coordinated action to mitigate and adapt to climate change will be essential for achieving the healthy, resilient, safe, sustainably harvested and biodiverse ocean that the UN Decade of Ocean Science and sustainable development goals (SDGs) seek. Ocean-based mitigation actions could contribute 12% of the emissions reductions required by 2030 to keep warming to less than 1.5ºC but, because substantial warming is already locked in, extensive adaptation action is also needed. Here, as part of the Future Seas project, we use a "foresighting/hindcasting" technique to describe two scenarios for 2030 in the context of climate change mitigation and adaptation for ocean systems. The "business-as-usual" future is expected if current trends continue, while an alternative future could be realised if we were to effectively use available data and knowledge to push as far as possible towards achieving the UN SDGs. We identify three drivers that differentiate between these alternative futures: (i) appetite for climate action, (ii) handling extreme events and (iii) climate interventions. Actions that could navigate towards the optimistic, sustainable and technically achievable future include: