Extreme weather events are increasing in frequency and intensity, but their ecological impacts remain less well understood than those of gradual climate change, largely owing to the challenge of studying unpredictable, short-lived events. The 2021 western North American heatwave is among the most extreme on record globally, yet a broad assessment of its ecological consequences is lacking. Here we synthesize meteorological, ecological, hydrological and wildfire data, along with process-based modelling, to quantify the heatwave and its impacts across the region. Our meta-analysis of 32 terrestrial and marine taxa reveals that over 75% were negatively impacted, but species responses ranged widely, from 99% declines to 89% increases. This variability reflects differences in organisms' thermal sensitivities, response capacities and exposures, with the latter dependent on geography, microclimate and refugia. Impacts tended to be greater for sessile marine invertebrates, algae and plants than for birds and mammals. At the ecosystem scale, changes in gross primary productivity ranged from 30% increases in cooler, wetter areas to 75% decreases in warmer, arid ones. Streamflow from snow and ice melt increased 40% during the heatwave before dropping below average, whereas wildfire activity surged 37% during the heatwave and 395% the following week. Our results underscore the urgent need for enhanced coordinated approaches to predict, detect and manage increasing heatwaves.

Natural climate solutions (NCS) are increasingly recognized as important for combatting climate change, but ocean-based pathways remain underrepresented in national strategies for conservation and climate change mitigation. Here, we present a transferable national assessment framework for blue carbon, applied to Canada, that maps blue carbon ecosystem extents, quantifies national carbon stocks and sequestration potential, and evaluates the benefits of increasing their spatial protection. We estimated that 10,952.5 Tg C (95% CI: 7,035.7 – 16,098.7 Tg C) is stored in the top 30 cm of Canada’s marine soils and sediments, with marine macrophytes, including kelp forests, additionally sequestering 7.7 Tg C yr-1 (95% CI: 5.6 – 25.1 Tg C yr-1). Expanding protection of blue carbon ecosystems to 30% by 2030, in line with the Kunming-Montreal Post-2020 Global Biodiversity Framework, could provide a practical pathway for incorporating blue carbon into national NCS portfolios. If current rates of habitat loss and disturbances were effectively abated in these areas, this could provide 106.9 Tg CO2e (95% CI: 94.1 – 234.9 Tg CO2e) in cumulative climate mitigation benefits by 2050. Our approach provides a foundation for integrating blue carbon into national climate and conservation strategies.

ABSTRACT The dual crises of climate change and biodiversity loss continue despite overwhelming scientific evidence of their impacts on human well‐being and planetary health. Those of us working in the fields of conservation and ecology are acutely aware that current efforts to avert these crises are profoundly inadequate. But how are we, as professionals working in these fields, responding? We engage in many different activities from generating knowledge and educating students to communicating research findings. Some of us work to implement science‐based evidence and advocate for policy change. A few of us engage in activism. In this perspective, we explore how to increase our impact by re‐prioritizing how we spend our time on various activities and focus our efforts on actions most likely to lead to positive change. We offer an exercise to self‐reflect and identify pathways to increase our impact. The escalating crises demand an urgent re‐think from us all in how we currently spend our time.

Climate change is restructuring ecological communities globally, yet the impacts are often underestimated or poorly resolved due to the lack of historical baselines. In temperate oceans, biologically diverse and socioeconomically important kelp forests are the marine ecosystem most threatened by climate change. However, long-term historical baselines for kelp forests are lacking and the processes driving community-level changes remain poorly resolved. Here, using recently discovered aerial imagery and subtidal quadrat data from 1972, we recreated historical baselines for kelps and associated benthic macroalgae in a global hotspot within the northern Salish Sea (British Columbia, Canada). We resurveyed the same sites in 2023 to quantify community shifts, showing that a half-century ago, bull kelp (Nereocystis luetkeana) formed expansive kelp forests in the region (>550 ha), none of which remain today. Satellite time series of bull kelp show that the majority was lost between 1972 and 1984. These data increase baselines of bull kelp canopy extent in this area by more than 10-fold. Changes to the benthic kelp forest assemblage were mainly driven by loss of the dominant kelp, Saccharina latissima (-78%), across all depths. Historically abundant species of red algae also decreased substantially (e.g., Mazzaella splendens [-98.5%] and Plocamium pacificum, [-62.1%]), largely above three meters depth. Applying the community temperature index (CTI) to this half-century comparison, we show that CTI of the kelp forest community (+1.4°C; 95% CI: 0.43-2.37°C) had tracked increases of summer SST (+1.66°C; 95% CI: 1.20-2.13°C) more closely than winter SST (+0.65°C; 95% CI: 0.46-0.84°C), indicating that temperatures during the hottest summer months are likely driving community shifts. The abundance of cold-affinity species decreased more than warm-affinity species abundance had increased, indicating that the subtidal kelp forest community was predominantly restructured by deborealization, rather than tropicalization. Community deborealization may be prevalent in temperate hotspots that are disjunct from areas with similar climatology, creating colonization barriers for warm-affinity species. Our study underscores the importance of historical data for understanding the true magnitude of climate change impacts and suggests that deborealization of temperate kelp forest communities may be more common than has previously been recognized.

Kelp forests are among the most extensive and productive coastal ecosystems, yet they remain underrepresented in global conservation policy despite widespread declines driven by interacting global- (i.e., ocean warming, marine heatwaves) to local-scale stressors. At the same time, kelp conservation and restoration efforts are expanding rapidly across regions, but measures of success and syntheses tend to primarily focus on ecological conditions and trends, not on conservation and restoration actions. To fill this gap, we developed a comparative global dataset of kelp conservation initiatives based on expert-derived regional narratives from 209 participants spanning 35 regions with kelp forests. We applied a structured presence–absence scoring framework across six domains: conservation actions, restoration approaches, governance actors, conservation objectives, social dimensions, and funding structures, supplemented by regional expert knowledge to enable cross-regional comparison. Across regions, conservation was characterised by strong emphasis on monitoring (86

Habitat complexity plays a critical role in coral reef ecosystems by enhancing habitat availability, increasing ecological resilience, and offering coastal protection. Structure-from-motion (SfM) photogrammetry has become a standard approach for quantifying habitat complexity in reef monitoring programs. However, a major bottleneck remains in the two-dimensional (2D) classification of benthic cover in three-dimensional (3D) models, where experts are required to manually annotate individual colonies and identify coral species or taxonomic groups. With recent advances in deep learning and computer vision, automated classification of benthic habitats is possible. While some semi-automated tools exist, they are often limited in scope or do not provide semantic segmentation. In this investigation, we trained a convolutional neural network with the ResNet101 architecture on three years (2015, 2017, and 2019) of human-annotated 2D orthomosaics from Kiritimati, Kiribati. Our model accuracy ranged from 71% to 95%, with an overall accuracy of 84% and a mean intersection of union of 0.82, despite highly imbalanced training data, and it demonstrated successful generalizability when applied to new, untrained 2023 plots. Successful automation depends on training data that captures local ecological variation. As coral monitoring efforts move toward standardized workflows, locally developed models will be key to achieving fully automated, high-resolution classification of benthic communities across diverse reef environments.

With the increased frequency of marine heatwaves and related coral mass mortality events, it is imperative that we improve our understanding of coral reef recovery processes including how benthic community compositions can change over time. Coral reef benthic communities are influenced by many abiotic factors, but on most reefs local anthropogenic disturbances overshadow these factors thus obscuring their influence. Here, we leverage a dataset from a coral reef with very minimal local anthropogenic disturbance - the uninhabited southern coast of the world's largest atoll (Kiritimati) - to assess spatial variation in benthic community composition three years after the mass coral mortality event driven by the 2015-2016 El Niño. Across forereef sites ranging from 7 to 22 m, scleractinian coral cover remained very low (6.9 +/- 0.4 % SE) while soft coral cover was < 1%. Coral cover was highest at deep sites (18-22 m compared to sites at 7-10 m depth) and exposed locations, where stress-tolerant corals likely made up a larger proportion of the coral community before the mass mortality event. Higher cover of crustose coralline algae at shallow exposed sites, fleshy macroalgae at deep sites, and turf algae at exposed locations were consistent with taxa-specific preferences for light, wave action, and sedimentation. The abundances of the most common genera of juvenile coral (Acropora and Pocillopora) were still low (< 1 juvenile colony per genus per site) and varied only with depth. These findings demonstrate how variation in pre-mortality coral composition can lead to differences in post-mortality benthic communities on low disturbance coral reefs. ### Competing Interest Statement The authors have declared no competing interest.

Coral reefs are threatened by climate change and chronic local human disturbances. Although some laboratory studies have investigated the effects of combined stressors, such as nutrient enrichment and heat stress, on growth and survival of early life stage corals, in situ studies remain limited. To assess the influence of multiple stressors on juvenile corals, we quantified densities of corals ≤ 5 cm at 18 forereef sites with different exposure levels to underlying chronic local human disturbance before, during, and after the 2015-2016 El Niño. This marine heatwave caused prolonged heat stress and devastating losses of coral cover on the shallow forereef's of Kiritimati, in the central equatorial Pacific Ocean. Here, we enumerated a total of 7732 juvenile corals from 13 different families. Over 80% of corals were from four families: 70% from Agariciidae, Merulinidae, or Poritidae, which all have stress-tolerant life history strategies, and 11% from Acroporidae which has a competitive life-history strategy. Both local disturbance and heat stress were significantly negatively related to juvenile coral densities. Prior to the heatwave, juvenile densities were on average 72% lower at the most disturbed sites (7.2 ± 1.9 m-2) compared to the least disturbed ones (15.3 ± 3.8 m-2). Overall, juvenile corals had a lower bleaching prevalence and lower mortality during the heatwave when compared to their adult counterparts. Still, the heatwave resulted in the loss of half (49%) of all juvenile corals, with those corals with competitive or weedy life history strategies undergoing greater declines than stress-tolerant ones. Although juvenile coral densities increased slightly in the year following the heatwave, the effect was statistically non-significant. Our results highlight the influence of chronic local anthropogenic and marine heatwaves on juvenile coral densities.

Climate change is causing significant losses of coastal foundation species globally, heightening the need for their restoration. Despite the urgency, it remains unclear if enhancing genetic diversity by using distant source populations will improve restoration outcomes, or if local sources will perform better regardless of their diversity. We conducted a reciprocal transplant with Giant kelp ( Macrocystis pyrifera ) between a warm and cool microclimate 7 km apart in Barkley Sound, British Columbia, and tracked survivorship and growth over 6 months. We seeded kelp gametophyte cultures from the warm and cool site onto small rocks (i.e. “green gravel”) in a nursery, then outplanted them into experimental plots nearby the sites where the parents were collected. The number of parents used to make the cultures was also manipulated (two vs. 10) to simulate different levels of genetic diversity (average heterozygosity). Overall, we found inconsistent evidence for local adaptation between microclimates, and possibly signs of maladaptation in kelp from the warm site. Kelp from the more genetically diverse population at the cooler site survived 16% better and grew 8% larger regardless of the outplant site. Kelp grew up to 223% larger at the cool site but had higher mortality due to either urchin grazing or gravel turnover from swell. Surprisingly, kelp produced from two‐parent cultures survived 278% better than kelp from 10‐parent cultures at 6 months, despite higher observed rates of selfing. Our study provides new insights into factors influencing the restoration of these important temperate coastal foundation species.

Globally, shellfisheries are increasingly important for food, nutrition, and livelihoods. However, sustainable management of these fisheries is threatened by human activities, including climate change, overexploitation, and disruptions to natural ecosystems. Indigenous archaeological records of shellfish are ubiquitous but underutilized data sources that could expand and inform current management practices by extending or providing missing baselines for how species populations and ecosystem interactions may have changed over time. Here, we merge palaeobiological and archaeological methodologies to evaluate relative abundances of crabs and their clam prey over the past 3000 years on western Vancouver Island in the Northeast Pacific. We examine archaeological and recent shells of butter (Saxidomus gigantea) and littleneck clams (Leukoma staminea) from three locations in the Broken Group Islands, (Barkley Sound, Vancouver Island, BC, Canada) and quantify relative crab relative abundance through time by examining predation traces on clam shells. Our results indicate crab and clam population resilience despite substantial localized human harvesting pressures over approximately 3000 years, with clams increasing in abundance over time despite sustained intensive harvest. In contrast to studies in other regions of the eastern Pacific that observed recent decreases in modern crab abundances, evidence from the Broken Group Islands suggests crab populations remain stable over 3000 years, with slight but non-significant increases since the 19th century. These results are consistent with the well-established, long-term relationships Indigenous people had with shellfish resources and underscore the importance of including archaeological and paleobiological data/approaches in current conservation efforts to understand human impacts on coastal resources and ecosystems.

Predicting changes in species distributions under climate change relies on high-quality climate projections. In this case study of coastal British Columbia, we prepare and evaluate two sets of climate data - a priori bias corrected and non bias corrected dynamically downscaled historical projections of Community Earth System Model 2 simulations. We compare these datasets with downscaled ERA5 reanalysis focusing on commonly used inputs to species distribution models (SDM), namely, bioclimatic (BIOCLIM) variables and climate extreme indices. Our results show improvements for mean BIOCLIM variables when a priori bias correction is applied. However, modest improvements are observed in terms of variability and extreme indices. Overall, our findings suggest that a priori bias corrected dynamically downscaled climate projections provide more accurate input to SDMs, and thus can improve the reliability of these important ecological models.

Marine conserved areas (MCAs) can provide a range of ecological and socio-economic benefits, including climate change mitigation from the protection and enhancement of natural carbon storage. Canada's MCA network is expanding to encompass 30% of its Exclusive Economic Zone by 2030. At present, the network aims to integrate climate change mitigation by protecting coastal vegetated blue carbon ecosystems (saltmarsh, seagrass, kelp). Here, we argue that incorporating unvegetated seabed sediments could bring similar benefits. Seabed sediments can store and/or accumulate high densities of organic carbon, and due to their large spatial extent, contain carbon stores orders of magnitude larger than coastal vegetated habitats. We estimate that currently designated MCAs encompass only 10.8% of Canada's seabed sediment organic carbon stocks on the continental margin, and only 13.4% of areas with high carbon densities. Proposed MCAs would cover an additional 8.8% and 6.1% of total stocks and high carbon areas, respectively. We identify an additional set of high-priority seabed areas for future research and potential protection, ranking their importance based on carbon stocks, proxies for lability, and ecological/biological significance. The incorporation of seabed sediments into MCA networks could support climate change mitigation by preventing future releases of stored carbon.

Mobile bottom fishing causes substantial disturbances to seabed sediments–one of the world’s largest organic carbon stores. We estimate that 2.1 and 32.0 Mt of carbon is disturbed by annual fishing activities in the Canadian Pacific and Atlantic, respectively. A net increase in carbon remineralisation from this disturbance could negatively impact the oceanic sink for CO 2 . Due to high uncertainty in estimating the scale of remineralisation, we construct a semiquantitative measure of relative carbon risk to describe potential differences between locations and fisheries. In the Pacific, shrimp trawling caused the largest total carbon disturbance and risk; groundfish trawling had large total disturbance but lowest mean disturbance and risk per unit effort (PUE); scallop dredging had the smallest total impacts but highest disturbance and risk PUE. In the Atlantic, shrimp trawling dominated total impacts; however, mean disturbance PUE was highest for scallop and clam dredging, and mean risk PUE was highest for groundfish trawling. High spatial variation in these results would allow a targeted management approach. While uncertainties remain, precautionary risk-based ecosystem management should be implemented.

Habitat degradation and overexploitation are key drivers of biodiversity loss globally. Negative, human-driven changes in habitat quality, species abundance, and community composition are well-documented across systems. While it is understood that human stressors destabilize consumer-resource interactions, how energy pathways and food webs may reorganize in hyperdiverse tropical systems in response to human disturbance remains poorly understood due to their complexity and past methodological limitations. Leveraging recent advances in molecular isotope techniques, we performed an ecosystem-scale natural experiment to evaluate how human disturbance reorganizes carbon pathways and trophic structure in a hyperdiverse tropical system, Kiritimati Island, the world's largest atoll. We specifically employed novel integrations of bulk tissue and amino acid-specific stable isotope analyses applied to six nominally generalist fish species sampled across Kiritimati's well-documented human disturbance gradient. Sampled fish species comprised 48% of carnivorous reef fish biomass. Essential amino acid stable carbon isotope (δ13CEAA) fingerprinting and Bayesian stable isotope mixing models indicated that the proportional contribution of the carbon sources supporting five of the six sampled fish species did not vary across the disturbance gradient. Energy disproportionately (>80%) originated from planktonic production and microbially reworked detritus for most species, with only minor contributions of carbon sourced from coral and epilithic algal matrices. Reef fish trophic ecology was also consistent across the atoll, with species maintaining isotopic niches (size and position) and trophic positions across the atoll despite significant human disturbance-mediated changes in community composition and habitat complexity. Our findings suggest that the energy channels connecting basal resources to upper trophic level generalist consumers can be highly conserved following significant human disturbance in hyperdiverse tropical systems. On coral atolls, specifically, robust planktonic or detrital energy channels may buffer nominally generalist carnivorous reef fishes from some negative effects of chronic local human disturbance, promoting the maintenance of dominant energy fluxes in disturbed habitats. These results illustrate that disturbance-mediated changes in ecosystem structure and function do not universally destabilize broad energy fluxes and trophic relationships in hyperdiverse ecosystems. On the contrary, there appear to be mechanisms that promote stability, such as broad reliance on system-dominant production sources.

Kelp forests offer substantial carbon fixation, with the potential to contribute to natural climate solutions (NCS). However, to be included in national NCS inventories, governments must first quantify the kelp-derived carbon stocks and fluxes leading to carbon sequestration. Here, we present a blueprint for assessing the national blue carbon capacity of kelp forests in which data synthesis and Bayesian hierarchical modeling enable estimates of kelp carbon production, storage, and export capacity from limited data. Applying this blueprint to Canada's extensive coastline, we estimate kelps hold 0.6 to 2.8 Tg C in short-term biomass, producing 1.1 to 6.2 Tg C yr-1, of which 0.04 to 0.4 Tg C yr-1 could be exported to the deep ocean. While modest compared to terrestrial sinks, our findings suggest kelps have comparable carbon sequestration to marine and freshwater wetlands, warranting further consideration in Canada's NCS inventories. Our transparent, reproducible blueprint represents an important step towards accurate carbon accounting for kelp forests.

Quantification and mapping of surficial seabed sediment organic carbon have wide-scale relevance for marine ecology, geology and environmental resource management, with carbon densities and accumulation rates being a major indicator of geological history, ecological function and ecosystem service provisioning, including the potential to contribute to nature-based climate change mitigation. While global analyses can appear to provide a definitive understanding of the spatial distribution of sediment carbon, regional maps may be constructed at finer resolutions and can utilise targeted data syntheses and refined spatial data products and therefore have the potential to improve these estimates. Here, we report a national systematic review of data on organic carbon content in seabed sediments across Canada and combine this with a synthesis and unification of the best available data on sediment composition, seafloor morphology, hydrology, chemistry and geographic settings within a machine learning mapping framework. Predictive quantitative maps of mud content, dry bulk density, organic carbon content and organic carbon density were produced along with cell-specific estimates of their uncertainty at 200 m resolution across 4 489 235 km2 of the Canadian continental margin (92.6 % of the seafloor area above 2500 m) (https://doi.org/10.5683/SP3/ICHVVA, Epstein et al., 2024). Fine-scale variation in carbon stocks was identified across the Canadian continental margin, particularly in the Pacific Ocean and Atlantic Ocean regions. Overall, we estimate the standing stock of organic carbon in the top 30 cm of surficial seabed sediments across the Canadian shelf and slope to be 10.9 Gt (7.0–16.0 Gt). Increased empirical sediment data collection and higher precision in spatial environmental data layers could significantly reduce uncertainty and increase accuracy in these products over time.

Ecological data are being opportunistically synthesised at unprecedented scales in response to the global biodiversity and climate crises. Such syntheses are often only possible through large-scale, international, multidisciplinary collaborations and provide important pathways for addressing urgent conservation questions. Although large collaborative data syntheses can lead to high-impact successes, they can also be plagued with difficulties. Challenges include the standardisation of data originally collected for different purposes, integration and interpretation of knowledge sourced across different disciplines and spatio-temporal scales, and management of differing perspectives from contributors with distinct academic and cultural backgrounds. Here, we use the collective expertise of a global team of conservation ecologists and practitioners to highlight common benefits and hurdles that arise with the development of opportunistic collaborative syntheses. We outline a framework of “best practice” for developing such collaborations, encompassing the design, implementation, and deliverable phases. Our framework addresses common challenges, highlighting key actions for successful collaboration and emphasizing the support requirements. We identify funding as a major constraint to sustaining the large, international, multidisciplinary teams required to advance collaborative syntheses in a just, equitable, diverse, and inclusive way. We further advocate for thinking strategically from the outset and highlight the need for reshaping funding agendas to prioritize the structures required to propel global scientific networks. Our framework will advance the science needed for ecological conservation and the sustainable use of global natural resources by supporting proto-groups initiating new syntheses, leaders and participants of ongoing projects, and funders who want to facilitate such collaborations in the future.

Coral reefs are in global decline primarily due to climate change. Herbivory is often viewed as key to maintaining coral-dominated reefs, and herbivore management is gaining traction as a possible strategy for promoting reef resilience. The functional impact of herbivorous fishes has typically been inferred from total biomass, but robust estimates of ecological processes are needed to better inform management targets. Here, we provide a framework to calculate rates of herbivory across Pacific reefs. We synthesized available observations of foraging metrics in relation to fish body size and found considerable variation, even among closely related species. We then applied these allometric functions to survey data and calculated rates of herbivory for acanthurids and scarines, which make up the vast majority of herbivorous fish biomass in the Pacific. Estimated rates of algal consumption, area scraped, and bioerosion varied across islands, with noticeable differences that may align with the relative influence of human population density among underlying herbivore functional groups. We found no evidence of compensatory relationships among herbivore processes whereby decreasing rates in one type of herbivory is offset by increasing rates in another. We observed nonlinear, positive relationships between fish biomass and rates of herbivory. Yet, for a given biomass, the corresponding rates of herbivory varied among regions, and we observed instances where islands with the greatest biomass did not also have the highest rates of herbivory. Islands with the largest size classes of herbivores did not consistently exhibit greater rates of herbivory, and we did not find a clear, consistent pattern between the number of fish species and corresponding rates of herbivore processes. Cropping Acanthurus spp. provided the greatest proportion of algal consumption at every island, yet no single species accounted for the majority of this process, whereas we identified parrotfish species that provided >75% of scraping or bioerosion at certain islands. Our results emphasize the importance of considering the species and size composition of herbivore assemblages when estimating processes, rather than relying on total biomass alone. Lastly, we highlight gaps in foraging observations and additional work needed to further broaden our ability to quantify the ecological processes of herbivores.