A sustainable blue economy may not be possible in Tanzania without cutting emissions

Highlights • Climate-adaptive marine spatial management is necessary to reduce negative impacts on nature reliant livelihoods. • We assessed climate-driven risks and opportunities for conservation, artisanal fisheries and seaweed farming across Tanzania. • Ocean modelling spatial meta-analysis was used to detect the emergence of a climate signal affecting these sectors. • Participatory mapping assessed how coastal communities may be perceiving climate-driven change in these areas. • Few areas exhibit climate resilience or opportunities for sectoral growth under higher emissions. • Climate-smart spatial management may promote adaptation in some of Tanzania’s most vulnerable coastal areas. Abstract Balancing blue growth with the conservation of wild species and habitats is a key challenge for global ocean management. This is exacerbated in Global South nations, such as Tanzania, where climate-driven ocean change requires delicate marine spatial planning (MSP) trade-offs to ensure climate resilience of marine resources relied upon by coastal communities. Here, we identified challenges and opportunities that climate change presents to the near-term spatial management of Tanzania's artisanal fishing sector, marine protected areas and seaweed farming. Specifically, spatial meta-analysis of climate modelling for the region was carried out to estimate the natural distribution of climate resilience in the marine resources that support these socially important sectors. We estimated changes within the next 20 and 40 years, using modelling projections forced under global emissions trajectories, as well as a wealth of GIS and habitat suitability data derived from globally distributed programmes. Multi-decadal analyses indicated that long-term climate change trends and extreme weather present important challenges to the activity of these sectors, locally and regionally. Only in few instances did we identify areas exhibiting climate resilience and opportunities for sectoral expansion. Including these climate change refugia and bright spots in effective ocean management strategies may serve as nature-based solutions: promoting adaptive capacity in some of Tanzania's most vulnerable economic sectors; creating wage-gaining opportunities that promote gender parity; and delivering some economic benefits of a thriving ocean where possible. Without curbs in global emissions, however, a bleak future may emerge for globally valuable biodiversity hosted in Tanzania, and for its coastal communities, despite the expansion of protected areas or curbs in other pressures. Growing a sustainable ocean economy in this part of the Global South remains a substantial challenge without global decarbonization.