Since 1979, the Arctic has been warming nearly four times faster than the global average (Rantanen et al., 2022). This cold part of the globe is shaped and characterized by frozen water in the form of sea ice, ice sheets, glaciers, ice on rivers and lakes, permafrost, and snow. However, the Arctic cryosphere is melting at an accelerating rate with profound consequences for the global climate as well as for Arctic nature and people (CAFF, 2013; CAFF, 2017; AMAP, 2017c; AMAP, 2021). In the short term, the changes cause massive ecosystem perturbations which feed back to the climate system with a potential to accelerate local to regional changes in climate and greenhouse gas emissions and affect regional to global-scale climate systems. The resulting impacts on Arctic ecosystem services, livelihoods and wellbeing are accelerating and will have far-reaching consequences for Arctic residents and local communities. Impacts include changes in food security, economic and social wellbeing, cultural preservation, safety, human health, cultural ecosystem services, sense of place, transportation and infrastructure (AMAP, 2017b; AMAP, 2017a; AMAP, 2018).

In this context, the Arctic Council decided to initiate a joint assessment to be conducted by the two Arctic Council working groups; AMAP (Arctic Monitoring Assessment Program) and CAFF (Conservation of Arctic Flora and Fauna) with the over-arching objective to “assess how climate change affects Arctic ecosystems and feedbacks and inform strategies for adaptation and resiliency”. As a part of this assessment, scientific experts have, in this Special Issue of Frontiers in Environmental Science, reviewed the scientific literature to address how the current climatic drivers affect Arctic ecosystems and how these changes feed back to the climate system. The papers include marine, terrestrial and freshwater ecosystems and cover a wide range of climate-induced changes.

Together, the reviews in this Special Issue highlight the rapid and widespread environmental changes unfolding across the Arctic. While a global reduction in fossil fuel emissions could slow these developments and provide valuable time for adaptation, many of the observed changes have already reached -or are approaching -tipping points beyond which they may become irreversible.

In the following, we synthesize the major trends and uncertainties in Arctic marine and terrestrial ecosystems, highlighting the need for coordinated monitoring, future planning and adaptations. In an accompanying editorial synthesis at the end of this Special Issue we summarize current status as portrayed by the papers presented here (Christensen et al., 2025).

As sea ice diminishes from the Arctic Ocean, marine algae experience larger ice-free areas and longer growing season (Ardyna and Arrigo, 2020; Attard et al., 2024). Sustained by increased influx of nutrients, net primary production in the Arctic Ocean has increased by 57% from 1998 to 2018 (Lewis et al., 2020). Whether this increase in plant production will contribute to higher production of fish, shellfish, marine mammals and seabirds, as well as increased sequestration and storage of carbon in the bottom sediments is, however, highly uncertain and depend on complex interactions between the climatic drivers and the marine ecosystem (Ardyna and Arrigo, 2020; Oziel et al., 2025) (Figure 1; Table 1).

The rich sub-Arctic marine ecosystems, such as the Barents and Bering Seas support some of the world’s richest fisheries, and one scenario under climate warming, is that these rich systems simply move north and replace the historically less productive high-Arctic and ice-dominated ecosystems. However, the massive perturbation triggered by warming, ocean acidification and the melting of the Arctic cryosphere is likely to push the marine ecosystem into less stable and undesirable states. In a worst-case scenario, the Arctic marine ecosystems could as a response to these drivers turn into simplified systems dominated by opportunistic algae, high microbial activity, low diversity of plants and animals, turbid waters and expanding low-oxygen areas (see Breitburg et al., 2018; Reusch et al., 2018). This situation mirrors the changes observed in coastal areas world-wide (Breitburg et al., 2018). However, while climate warming, human eutrophication and over-fishing are the culprits in warmer seas, the changes in the Arctic are currently governed by ice-melting, seawater freshening, nutrient input, ocean acidification and warming (Figure 1).

The outcome of the climate-induced changes would depend on the initial state of the ecosystem, the pace and magnitude of the environmental changes, and not least the evolving pressures from emerging human activities in the Arctic, including increased pressures from fishing (Fauchald et al., 2021). To effectively document and understand ongoing changes, coordinated pan-Arctic monitoring and predictive modeling of climatic drivers and marine ecosystem responses are essential. In addition, it is crucial to assess how emerging human activities—such as industrial fishing, shipping, tourism, and the extraction of oil and mineral resources—interact with climate drivers to change the ecosystems. Equally important is the co-creation of scenarios, pathways, and solutions that support a more sustainable future for the Arctic Ocean.

In response to permafrost thaw, shorter periods with snow cover, and warmer summers, the tundra has gradually become greener over the past 40 years (Frost et al., 2025). The Arctic greening serves as a proxy for increased production and biomass of plants, reflecting a shift in vegetation cover, often linked to the expansion of deciduous shrubs. This “borealization” of the terrestrial Arctic ecosystem is occurring alongside a range of ecological disturbances that are expected to intensify in the coming decades, including wildfires (Baltzer et al., 2025), insect outbreaks (Vindstad et al., 2019), and extreme climatic events (Christensen et al., 2021).

The climate induced changes in the tundra ecosystem feed back to the climate system through biotic process such as microbial activity and herbivory (Schmidt et al., 2024). The most significant of these feedbacks is linked to permafrost thaw (Schuur et al., 2022). The Arctic permafrost holds approximately one-third of the world’s soil organic carbon (Schuur et al., 2015). As it thaws, this carbon becomes exposed to microbial decomposition, releasing carbon dioxide and methane into the atmosphere. These greenhouse gas emissions further accelerate global warming, creating a reinforcing feedback loop. The strength of this climate feedback depends on the magnitude of the emissions, the ratio of methane to carbon dioxide released (Parmentier et al., 2024), and the extent to which these emissions are offset by increased carbon uptake by accumulated plant biomass through Arctic greening (Schuur et al., 2022; See et al., 2024; López-Blanco et al., 2025).

Above the permafrost, the tundra holds a relatively thin and wet active layer, where most microbial and hydrological activity takes place. As the underlying permafrost thaws, the active layer deepens, altering tundra hydrology by promoting the drainage of soil, wetlands, and shallow lakes. These changes in Arctic hydrology could cause atmospheric climate feedback through reduction in cloudiness, which can be in the same order of magnitude as the permafrost carbon feedback (de Vrese et al., 2023; de Vrese et al., 2024). Moreover, the drainage of the tundra causes a shift to more aerobic microbial activity, resulting in reduced methane emissions relative to carbon dioxide (Parmentier et al., 2024). Finally, expanding woody vegetation, drier soils and increased lightning activity are contributing to more frequent, intense, and widespread Arctic wildfires (Kim et al., 2024; Baltzer et al., 2025). Besides having a pervasive effect on the vegetation (Heim et al., 2025), wildfires promote further melting of the permafrost and increase the emission of greenhouse gasses and aerosols.

Feedback loops between the ecosystem and the climate system, lagged ecosystem responses, and massive perturbations from wildfires, changed hydrology, species invasions and a thawing cryosphere will cause abrupt, unexpected and pervasive shifts in Arctic terrestrial ecosystems (Figure 2; Table 2). The magnitude of potential impacts, combined with significant uncertainties, underscores the need for a precautionary approach to development of human activities. Effective policy must be grounded in continuously updated knowledge drawn from coordinated pan-Arctic monitoring and predictive modeling, as well as future scenarios and preferred pathways co-developed by local residents and scientific experts. The spatial heterogeneity across Arctic regions offers valuable opportunities for shared learning, where regional experiences, local and indigenous knowledge, and bottom-up adaptations can inform and strengthen a collective response to ongoing changes.

Climate change is driving profound transformations in Arctic marine ecosystems, with increased primary production but growing risks of biodiversity loss and ecosystem instability. While boreal species may expand northward, potentially benefiting fisheries, this shift could disrupt food webs and reduce ecosystem resilience. Ocean acidification, deoxygenation, and harmful algal blooms threaten marine life and carbon storage capacity. Regional outcomes will depend on ecosystem vulnerability, climate dynamics, and human activities such as fishing, shipping and resource extraction. In this regard, cross-sector adaptation planning through ecosystem-based management by national and local governments could play a key role. There is a need for policymakers to prioritize coordinated pan-Arctic monitoring, scenario development, and adaptive and sustainable governance to safeguard the future of the Arctic Ocean.

Arctic terrestrial ecosystems are undergoing rapid and unpredictable transformations due to permafrost thaw, vegetation shifts, and intensifying disturbances such as wildfires and extreme weather. These changes create powerful climate feedbacks, notably through greenhouse gas emissions from thawing permafrost, which risk accelerating global warming. The spatially variable and lagged responses of ecosystems complicate predictions and demand flexible, regionally informed policy approaches. A precautionary stance is essential, supported by coordinated pan-Arctic monitoring, scenario planning, and inclusive co-development with local communities. Policymakers must integrate scientific and indigenous knowledge to guide sustainable Arctic development under growing uncertainty.

To effectively prepare for, navigate, and adapt to these transformations, we argue that the Arctic States, through the Arctic Council, should take the following three actions:

Establish coordinated pan-Arctic monitoring and predictive modeling of key climatic drivers, human activities, and their combined impacts on Arctic socio-ecological systems. This action should include: