The Arctic region, a pivotal component of the Earth's climate system, is experiencing rapid and unprecedented changes driven by climate change (Meredith et al. 2019 IPCC).The Arctic Council has, through its report to Ministers in 2019, acknowledged that climate change will affect ecosystems and ecosystem services and that this is key to human livelihoods in the Arctic.As a follow up on this the Arctic Council, through its working groups Arctic Monitoring and Assessment Programme (AMAP) and Conservation of Arctic Flora and Fauna (CAFF), decided to initiate an assessment and a process with a focus on how climate change affects Arctic ecosystems and feedbacks and inform strategies for adaptation and resiliency. Forming part of this assessment process this special issue investigated the complex dynamics of Arctic ecosystems, focusing on marine, terrestrial, and atmosphere-ecosystem interactions. As sea ice diminishes and temperatures increase, the equilibrium of these ecosystems is disrupted, resulting in significant alterations in biodiversity, species distribution, and ecological processes. This collection of studies elucidates the critical role of ice algae in marine food webs, the intricate feedback loops between tundra ecosystems and the climate, and the importance of methane emissions in global climate feedback mechanisms. By addressing key knowledge gaps and emphasizing the necessity for adaptive management strategies, this issue provides a comprehensive understanding of the challenges and opportunities confronting Arctic ecosystems in the context of a rapidly changing environment.The role of the productivity of Arctic marine ecosystems is crucial. Here ice algae play an important role and particularly in their contributions to both benthic and pelagic food webs amidst changing sea ice conditions (Niemi et al. 2024). Ice algae serve as a high-quality carbon source for benthic organisms, especially during the ice melt period, which triggers benthic growth and reproduction. Further research is needed to understand the dynamics of ice algae production, degradation, and their interactions with other carbon sources to fully grasp their impact on ecosystem functioning. Importantly, more research is needed to understand the consequences of climate induced changes in sea-ice dynamics for ice algae supply and the sympagic-benthic-pelagic coupling. Pecuchet et al. (2025) reviews the increasing frequency, intensity, and duration of marine heatwaves (MHWs) in the Arctic and Subarctic regions, highlighting their unique dynamics influenced by sea ice and ocean-atmospheric interactions. Sea ice loss and narrow thermal niches of high-arctic organisms make the Arctic marginal seas highly exposed and vulnerable to MHWs. The ecological impacts of MHWs are significant and include shifts in species distribution, declines in marine life, and alterations in food webs. It emphasizes the need for long-term studies to understand the cumulative effects of MHWs and their interactions with other climate variables and human activities (Pecuchet et al. 2025) and calls for adaptive management strategies to enhance ecosystem resilience against MHWs.Climate change impacts the migratory patterns of Arctic marine vertebrates, including fishes, seabirds, and marine mammals, by altering resource availability and ecosystem dynamics due to declining sea ice, more open water patterns as well as changing ocean conditions (Kuletz et al. 2024) . These changes affect the timing and spatial extent of the northward migration during summer with consequences for the endemic Arctic ecosystems. The reduction of sea ice will also influence human activities with increase in vessel traffic, oil, gas and mining exploration and extractions etc. that can affect spatial distributions and migratory patterns of endemic Arctic species, including species of importance to local and indigenous communities and lifestyle. Conservation strategies are therefore necessary to address these challenges, with particular attention to the implications for indigenous communities reliant on these species.In Arctic and Subarctic ecosystems, climate change-induced migration patterns of marine vertebrates highlight the phenomenon of borealization discussed in a further paper in this issue (Husson et al. 2024), where Arctic ecosystems acquire characteristics typical of southern boreal ecosystems. Species redistribution driven by thermal preferences leads to significant changes in biodiversity and ecosystem functioning. Adaptive management strategies are essential to address the ecological and socio-economic consequences of these changes, especially for local human communities dependent on these ecosystems.Biotic interactions play a critical role in shaping feedback loops between tundra ecosystems and the climate system, especially in the context of rapid Arctic climate change. Schmidt et al. (Schmidt et al. 2024) identify key feedback loops between climate and tundra ecosystems as albedo, carbon dynamics, and permafrost thaw and how vegetation, decomposers and herbivores significantly influence these processes. Current ecosystem models often neglect these biotic influences, leading to inaccurate predictions of ecosystem responses to climate change. A comprehensive understanding of these interactions is essential for improving the accuracy of climate and ecosystem models.Significant environmental changes are occurring in Arctic landscapes, particularly concerning soil carbon dynamics and vegetation greenness. The unprecedented summer of 2023, marking the first time global temperatures exceeded 1.5°C, underscores the urgent need to understand also the implications of extreme fire regimes on biodiversity and ecosystem functions (Baltzer et al. 2025). Changing fire regimes affect the ecological resistance and resilience of boreal ecosystems, with pyrodiversity and post-fire residual vegetation playing important roles. While large boreal wildfires can enhance biodiversity through varied burn severity, they also pose risks of compositional changes and recruitment failures in forest ecosystems.) presents a spatial analysis showing there is a small spatial overlap between hydroclimate and ecosystem monitoring. In-situ monitoring of climate and hydrological variables is in general sparse, especially at higher latitudes. The catchment-based approach is recommended for studying hydroclimate-ecosystem interactions, but its application is limited due to the spatial mismatch in monitoring data. Some regions with dense monitoring networks can serve as starting points for catchment-based studies, such as northern Fennoscandia, Greenland, Alaska, and parts of Canada and Russia (Mård et al. this issue).Methane emissions from the Arctic-Boreal region, encompassing both terrestrial and marine sources such as wetlands, lakes, and permafrost, play a significant role in global climate feedback mechanisms. Anaerobic conditions in organic soils, particularly in waterlogged environments, facilitate methanogenesis. Parmentier et al. ( 2024) discuss the uncertainties surrounding future methane emissions due to climate change and the complex interactions between various environmental factors. Disturbances like wildfires and animal activity also impact methane dynamics, highlighting the need for a comprehensive understanding of methane sources and sinks.Interactions between climate change, aeolian dust, and Arctic ecosystems are crucial, with dust playing a significant role in ecological processes. Understanding carbon cycling patterns, particularly in relation to permafrost thaw and greenhouse gas dynamics, is crucial. Discrepancies between bottom-up and top-down greenhouse gas estimates highlight the need for improved modeling approaches. Enhanced research is necessary to accurately quantify greenhouse gas budgets in permafrost regions. Catchment scale studies are highly appropriate for such studies as also discussed by Mård et al. (this issue).There are significant knowledge and data gaps regarding the spatial and temporal extent of borealization across the Arctic, particularly in the Siberian seas and Canadian Arctic regions. Limited data availability is noted for winter and polar night processes, as well as transition periods between ice-free and ice-covered seasons. The understanding of microbial communities, epibenthos, and infauna is underdeveloped, necessitating more research resources to characterize these ecosystem components. The adaptive capacities of species to climate change and their phenotypic plasticity remain poorly understood, impacting predictions of species responses.Amid climate change, there is limited understanding of how altered spatial organization and migratory patterns in Arctic shelf and pelagic ecosystems affect predator-prey relationships, inter and intra specific competition and food web dynamics. The impacts of increased human activity in previously ice-covered areas on Arctic ecosystems remain underexplored. The adaptability of Arctic marine vertebrates to unpredictable physical and biological conditions is not fully understood, necessitating further research.There are substantial knowledge gaps regarding the subsurface mechanisms of marine heatwaves (MHWs) in Arctic regions. The predictability and forecasting of MHWs in the Arctic remain poorly understood. Challenges exist in identifying MHWs due to sea ice cover limiting open-water days.Defining relevant MHW thresholds is difficult due to low sea temperature variability. Further research is needed on the detection and mechanisms of MHWs in polar regions. The ecological impacts of MHWs on various taxa are still not fully understood. There is a need to improve predictive models for better management and conservation strategies.Focused research is needed to predict future coupling between marine sub-webs, considering trophic markers of multiple carbon sources due to ongoing sea-ice change. The extent to which ice algal supply increases with multi-year ice replacement requires further investigation, particularly regarding the photophysiology of ice-algal species. The impact of variations in ice algae supply on benthic biodiversity and biomass, as well as the responses to changing food source diversity and predatorprey interactions, necessitates mechanistic studies. Understanding the influence of light-driven phenology on ice algae production, degradation, and quality is critical.There is a significant research gap in the integration of biotic influences into climate and ecosystem models, particularly regarding feedback loops between tundra ecosystems and the atmosphere. A thorough meta-analysis on biotic influences on feedback loops in high-latitude ecosystems is needed, focusing on the magnitude and direction of impacts. Many biotic influences appear patchy in space and time, hindering a comprehensive understanding of their roles in ecosystem responses to climate change. Capturing complex feedback networks and interactions between biotic and abiotic components in future modeling efforts is essential.The strength and longevity of greening trends, local declines in productivity, and the impact of disturbances and extreme events remain uncertain. Key knowledge gaps and uncertainties persist concerning the historical and future state of tundra ecosystems and their connection to spatiotemporal variability in greening trends. Improved integration of field-based datasets, particularly outside traditionally well-studied areas, is needed, currently hindered by access and collaboration barriers. Understanding how intensifying disturbances will interact with climate-driven greening over the long term is crucial.Key knowledge gaps regarding the direct effects of changing fire regimes on wildlife taxa necessitate additional baseline data collection to better understand these impacts. There is an urgent need to improve understanding of the impacts of burning conditions experienced in 2023 on northern habitats and associated wildlife communities. The complexities between climate, wildfire, and vegetation, as well as their direct and indirect effects, require further exploration to inform conservation and management actions. Developing ecological forecasting tools to anticipate land cover changes and their impacts on wildlife is essential.There is a significant lack of in-situ monitoring stations for key hydroclimate variables like precipitation and snow cover, particularly in remote and northern areas. Groundwater monitoring is primarily conducted near research stations and municipal areas, with limited data sharing and representation of larger spatial variations. Ecosystem monitoring is concentrated around accessible regions and research stations, leading to potential biases in understanding Arctic ecosystems.There is a significant lack of knowledge regarding the total surface area and location of wetlands, which hampers accurate methane budget assessments in the Arctic-Boreal region. This has led to reliance on outdated wetland maps. Further, temporal data gaps, particularly in winter, are problematic as they may account for up to half of annual emissions. The heterogeneous nature of Arctic landscapes complicates current monitoring efforts, making upscaling and process modeling challenging. The temperature-dependent consumption of atmospheric methane by dry soils adds further uncertainty to emission estimates.A better understanding of the complex counterbalancing feedback related to Arctic dust is needed, particularly how increased dust emissions affect climate interactions. There is a lack of characterization of low latitude dust source emissions, such as road and agricultural dust, complicating the interpretation of dust loadings. Future research should focus on the optical properties of various dust types compared to black carbon to estimate their climatic significance. Cross-sectional networking among atmospheric dust experts and soil and cryospheric experts is essential for identifying current and future dust source locations and particle properties.Significant gaps exist in the spatial and temporal coverage of in-situ greenhouse gas (GHG) measurements, particularly during winter and shoulder seasons. At the catchment scale uncertainties surrounding lateral methane transport from wet tundra, lakes and peatlands are compounded by a limited understanding of dissolved methane dynamics, necessitating further investigation. The roles of winter fluxes, lateral transport of carbon, disturbance regimes, and herbivore interactions in the Net Ecosystem Carbon Balance (NECB) of Arctic-boreal ecosystems require greater attention to reduce discrepancies in GHG estimates.The papers in this special issue have outlined both specific and broader recommendations for future research. In the policy brief that introduced the special issue, a number of action points were identified (Fauchald et al., this issue). Here these action points are merged with foci identified in the individual papers. These foci should advance the overarching theme of fostering further efforts at the intersection of biodiversity, ecosystem studies, and cumulative climate feedbacks. The suggestions include: To further quantify changes in ice algae and assess impacts on trophic structures and phenology effects. To investigate benthic species adaptability to changing food sources and long-term climate impacts on migratory patterns. To develop monitoring programs for shifting migratory routes, new wintering areas, and interactions during migrations, as part of a coordinated pan-Arctic monitoring effort. To work on the detection, mechanisms, and effects of marine heatwaves (MHWs) on species resilience and interactions with stressors. To improve predictive models for ocean carbon cycle, borealization extent, nutrient limitations, and integrate biotic interactions and feedback loops. To improve predictive models for changes in migration patterns and distribution of species of importance for local and indigenous communities as well as species of socioeconomic and cultural importance. To adapt monitoring to ecosystem components of local community importance and study socioeconomic consequences of ecological transformations, including capacity building for ecosystembased management. To prioritize coordinated ecological and hydroclimatic monitoring in regions most vulnerable to climate change to improve spatial coverage and data quality, supported by a central data repository and online knowledge hub. To utilize advances in satellite remote sensing, drones, and machine learning to enhance monitoring capabilities and fill spatial gaps. To focus on smaller catchments or sub-catchments with available monitoring data to improve detection, interpretation, and projection of linked hydroclimate-ecosystem dynamics. To foster cross-disciplinary research efforts to better understand the complex interactions between climate, cryosphere, water, and ecosystems in the Arctic. To investigate relationships between vegetation changes, soil food webs, carbon dynamics, and greening trends. To advance novel sensor capabilities and integrated monitoring approaches for GHG budgeting and flux measurements.
Christensen et al. (Wed,) studied this question.