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Abstract Kelp forests are one of the earth’s most productive ecosystems and are at great risk from climate change, yet little is known regarding their current conservation status and global future threats. Here, by combining a global remote sensing dataset of floating kelp forests with climate data and projections, we find that exposure to projected marine heatwaves will increase ~6 to ~16 times in the long term (2081–2100) compared to contemporary (2001–2020) exposure. While exposure will intensify across all regions, some southern hemisphere areas which have lower exposure to contemporary and projected marine heatwaves may provide climate refugia for floating kelp forests. Under these escalating threats, less than 3% of global floating kelp forests are currently within highly restrictive marine protected areas (MPAs), the most effective MPAs for protecting biodiversity. Our findings emphasize the urgent need to increase the global protection of floating kelp forests and set bolder climate adaptation goals. 

ABSTRACT Under accelerating threats from climate‐change impacts, marine protected areas (MPAs) have been proposed as climate‐adaptation tools to enhance the resilience of marine ecosystems. Yet, debate persists as to whether and how MPAs may promote resilience to climate shocks. Here, we use 38 years of satellite‐derived kelp cover to empirically test whether a network of 58 temperate coastal MPAs in Central and Southern California enhances the resistance of kelp forest ecosystems to, and their recovery from, the unprecedented 2014–2016 marine heatwave regime that occurred in the region. We also leverage a 22‐year time series of subtidal community surveys to mechanistically understand whether trophic cascades explain emergent patterns in kelp forest resilience within MPAs. We find that fully protected MPAs significantly enhance kelp forests' resistance to and recovery from marine heatwaves in Southern California, but not in Central California. Differences in regional responses to the heatwaves are partly explained by three‐level trophic interactions comprising kelp, urchins, and predators of urchins. Urchin densities in Southern California MPAs are lower within fully protected MPAs during and after the heatwave, while the abundances of their main predators—lobster and sheephead—are higher. In Central California, a region without lobster or sheephead, there is no significant difference in urchin or kelp densities within MPAs as the current urchin predator, the sea otter, is protected statewide. Our analyses show that fully protected MPAs can be effective climate‐adaptation tools, but their ability to enhance resilience to extreme climate events depends upon region‐specific environmental and trophic interactions. As nations progress to protect 30% of the oceans by 2030, scientists and managers should consider whether protection will increase resilience to climate‐change impacts given their local ecological contexts, and what additional measures may be needed. 

Blue food systems are crucial for meeting global social and environmental goals. Both small-scale marine fisheries (SSFs) and aquaculture contribute to these goals, with SSFs supporting hundreds of millions of people and aquaculture currently expanding in the marine environment. Here we examine the interactions between SSFs and aquaculture, and the possible combined benefits and trade-offs of these interactions, along three pathways: (1) resource access and rights allocation; (2) markets and supply chains; and (3) exposure to and management of risks. Analysis of 46 diverse case studies showcase positive and negative interaction outcomes, often through competition for space or in the marketplace, which are context-dependent and determined by multiple factors, as further corroborated by qualitative modeling. Results of our mixed methods approach underscore the need to anticipate and manage interactions between SSFs and aquaculture deliberately to avoid negative socio-economic and environmental outcomes, promote synergies to enhance food production and other benefits, and ensure equitable benefit distribution. 

The COVID-19 pandemic exposed the fragility of global and domestic seafood markets. We examined the main impacts and responses of the small-scale fisheries (SSF) sector, and found that mitigation and preparedness strategies should be prioritised to boost resilience in SSF. We provide five policy options and considerations: (1) improving access to insurance and financial services; (2) strengthening local and regional markets and supporting infrastructure; (3) recognising fisheries as an essential service; (4) integrating disaster risk management into fisheries management systems; and (5) investing in Indigenous and locally-led fisheries management. Response and recovery measures need to explicitly build strategies to maintain or boost inclusion and equity in SSF. 

The global food production system is increasingly strained by abrupt and unpredictable weather events, which hinder communities' ability to adapt to climate variations. Despite advances in meteorological predictions, many communities lack the academic knowledge or infrastructure to interpret these complex models. This gap highlights the need for solutions that make climate forecasts more accessible and actionable, especially for communities reliant on natural resources. This study explores the potential of enhancing seasonal climate forecasts by integrating local ecological knowledge (LEK) with scientific data. Specifically, we combined ethnobiological information gathered between 2022 and 2024 with existing oceanographic and ecological data to create an ethnobiological calendar for four fishing cooperatives. An ethnographic approach was used to understand the population's ethnobiological knowledge and their perceptions of marine heatwaves and climate change impacts. Coastal monitoring data was collected using moorings that recorded temperature over a 14-year period (2010–2024). To characterize giant kelp dynamics, we used an existing dataset of multispectral Landsat images, which estimates the surface canopy biomass of giant kelp forests. Ecological monitoring was conducted annually every summer from 2006 to 2023 to record the in situ abundance of ecologically and economically important invertebrate and fish species. Combining oceanographic, ecological, and ethnographic data, allowed for alligning fishers' observations with recorded marine heatwave events and ecological shifts. Our findings revealed that these observations closely matched documented marine heatwave data and corresponding ecological changes. The integration of LEK with scientific oceanographic data can significantly improved our understanding of dynamic climate regimes, offering contextually relevant information that enhances the reliability and utility of seasonal climate forecasts. By incorporating yearly data into an ethnobiological calendar, we promote more inclusive, community-based approaches to environmental management, advocating for the integration of LEK in climate adaptation efforts, emphasizing its crucial role in strengthening resilience strategies against climatic shocks. 

Ocean warming is increasing organismal oxygen demand, yet at the same time the ocean’s oxygen supply is decreasing. For a patch of habitat to remain viable, there must be a minimum level of environmental oxygen available for an organism to fuel its metabolic demand—quantified as its critical oxygen partial pressure (pO_2crit). The temperature-dependence ofpO_2critsets an absolute lower boundary on aerobically viable ocean space for a species, yet whether certain life stages or geographically distant populations differ in their temperature-dependent hypoxia tolerance remains largely unknown. To address these questions, we used the purple sea urchinStrongylocentrotus purpuratusas a model species and measuredpO_2critfor 3 populations of adult urchins (Clallam Bay, WA [n = 39], Monterey Bay, CA [91], San Diego, CA [34]) spanning 5-22°C and for key embryonic and larval developmental phases (blastula [n = 11], gastrula [21], prism [31], early-pluteus [21], late-pluteus [14], settled [12]) at temperatures of 10-19°C. We found that temperature-dependent hypoxia tolerance is consistent among adult populations exposed to different temperature and oxygen regimes, despite variable basal oxygen demands, suggesting differential capacity to provision oxygen. Moreover, we did not detect evidence for a hypoxia tolerance bottleneck for any developmental phase. Earlier larval phases are associated with higher hypoxia tolerance and greater temperature sensitivity, while this pattern shifts towards lower hypoxia tolerance and reduced temperature sensitivity as larvae develop. Our results indicate that, at least forS. purpuratus,models quantifying aerobically viable habitat based onpO_2crit-temperature relationships from a single adult population will conservatively estimate viable habitat.