The Earth’s climate is strongly affected by the partitioning of carbon between its mobile reservoirs, primarily between the atmosphere and the ocean. The distribution between the reservoirs is being massively perturbed by human activities, primarily due to fossil fuel emissions, with a range of consequences, including ocean warming and acidification, sea-level rise and coastal erosion, and changes in ocean productivity. These changes directly impact valuable habitats in many coastal regions and threaten the important services the habitats provide to mankind. Among the most productive and diverse systems are coral reefs and vegetated habitats, including saltmarshes, seagrass meadows, and mangroves. Coral reefs are particularly vulnerable to ocean warming and acidification. Vegetated habitats are receiving heightened attention for their ability to sequester carbon, but they are being impacted by land-use change, sea-level rise, and climate change. Overall, coasts play an important, but poorly quantified, role in the global cycling of carbon. Carbon reservoirs on land and in the ocean are connected through the so-called land–ocean aquatic continuum, which includes rivers, estuaries, and the coastal ocean. Terrestrial carbon from soils and rocks enters this continuum via inland water networks and is subject to transformations and exchanges with the atmosphere and sediments during its journey along the aquatic continuum. The expansive permafrost regions, comprised of ground on land and in the seabed that has been frozen for many years, are of increasing concern because they store vast amounts of carbon that is being mobilized due to warming. Quantitative estimates of these transformations and exchanges are relatively uncertain, in large part because the systems are diverse and the fluxes are highly variable in space and time, making observation at the necessary spatial and temporal coverage challenging. But despite their uncertainty, existing estimates point to an important role of these systems in global carbon cycling.
Katja Fennel, Tyler Cyronak, Michael DeGrandpre, David T. Ho, Goulven G. Laruelle, Damien Maher, and Julia Moriarty
The fish fauna of the Baltic Sea reflects its 9 KY history of Arctic and temperate conditions and is a mixture of species that have invaded from the Atlantic and the continental watersheds. In spite of the challenging environmental conditions, such as low salinity in the entire Baltic Sea and varying temperature conditions, limiting the possibilities for successful reproduction, the number of species is comparably high. Except for the Baltic Ice Lake and certain stages of the cold Yoldia Sea and freshwater Ancylus Lake, the fish fauna of the Baltic Sea, as recorded by archaeological and historical notes, has to a large extent remained unchanged. Some freshwater and cold-water species such as Arctic char may have disappeared while others, such as fourhorned sculpin and eelpout, have adapted and persist as “ice age relicts.” There are few viable introductions of novel species; the round goby may be the most conspicuous invasive species. The extinction rate is still low; the loss of sturgeon and the common skate within the HELCOM (the Helsinki Commission) area is due to fishing, and, for the riverine sturgeon, due to damming. Since the formation of the Baltic Sea, fishing has played an essential role in supplying coastal settlements and their hinterlands and in trading. The archaeological and historical records have indicated fishing conducted with varying intensity using different methods. Herring fishing has been a significant economic driver from the Middle Ages onward. Recent archaeological findings indicate that organized fishing was established at the outer archipelagos along the present Swedish east coast on predominately herring and cod archipelagos for self-sufficiency shortly before or during the Viking Age, and later to engage in barter. The fact that the cod abundance has sometimes been sufficient for letting cod fishing be the most important fishery in the northern Baltic Proper alongside the fishery on herring may indicate that the eastern cod stock had relatively high productivity even when the Baltic Sea was significantly less eutrophic than it has been since the mid-20th century. This preindustrial variability in cod abundance suggests that climatic changes leading to changes in inflows of oceanic water may have affected salinity levels in the Baltic Sea. Fisheries show substantial variability, especially over the last century. Fish production may have increased due to nutrient enrichment of the Baltic Sea. Higher yields have also been obtained due to higher fishing intensity and technological changes. Fishing has, therefore, become a major driver in shaping fish stocks. The eutrophication of the Baltic Sea, leading to higher primary productivity and increasing water temperature and reductions in ice cover, may have led to changes in ecosystem structure and productivity. It should be underscored that such changes may also be amplified by the increasing fishing pressure on the cornerstone species such as herring, leading to significant disruptions in the food web.
Elisabeth Lipiatou and Anastasios Kentarchos
Although the first European Union Framework Programme (FP) for research and technological development was created in 1984, it was the second FP (FP2) in 1987 that devoted resources to climatological research for the first time. The start of FP2 coincided with the establishment of the Intergovernmental Panel on Climate Change in 1988, aimed at providing a comprehensive assessment on the state of knowledge of the science of climate change. FP-funded research was not an end in itself but a means for the European Union (EU) to achieve common objectives based on the principle of cross-border research cooperation and coordination to reduce fragmentation and effectively tackle common challenges. Since 1987, climate science has been present in all nine FPs (as of 2023) following an evolutionary process as goals, priority areas, and financial and implementation instruments have constantly changed to adapt to new needs. A research- and technology-oriented Europe was gradually created including in the area of climate science. There has historically been a strong intrinsic link, there has been a strong, intrinsic link between research and environmental and climate policies. Climate science under the FPs, focusing initially on oceans, the carbon cycle, and atmospheric processes, has increased tremendously both in scope and scale, encompassing a broad range of areas over time, such as climate modeling, polar research, ocean acidification, regional seas and oceans, impacts and adaptation, decarbonization pathways, socioeconomic analyses, sustainability, observations, and climate services. The creation and evolution of the EU’s FPs has played a critical role in establishing Europe’s leading position on climate science by means of promoting excellence, increasing the relevance of climate research for policymaking, and building long-lasting communities and platforms across Europe and beyond as international cooperation has been a key feature of the FPs. No other group of countries collaborates on climate science at such scale. Due to their inherited long-term planning and cross-national nature, the FPs have provided a stable framework for advancing climate science by incentivizing scientists and institutions with diverse expertise to work together, creating the necessary critical mass to tackle the increasing complex and interdisciplinary nature of climate science, rationalizing resource allocation, and setting norms and standards for scientific collaboration. It is hard to imagine in retrospect how a similar level of impact could have been achieved solely at a national level. Looking ahead and capitalizing on the rich experience and lessons learned since the 1980s, important challenges and opportunities need to be addressed. These include critical gaps in knowledge, even higher integration of disciplines, use of new technologies and artificial intelligence for state-of-the-art data analysis and modeling, capturing interlinkages with sustainable development goals, better coordination between national and EU agendas, higher mobility of researchers and ideas from across Europe and beyond, and stronger interactions between scientists and nonscientific entities (public authorities, the private sector, financial institutions, and civil society) in order to better communicate climate science and proactively translate new knowledge into actionable plans.
Harald Pauli and Stephan R.P. Halloy
High mountains (i.e., mountains that reach above the climatic treeline) are regions where many interests converge. Their treeless alpine landscapes and ecosystems are key areas for biodiversity, they act as water sources and reservoirs, and they are cultural and religious icons. Yet, mountain environments are threatened by global stressors such as land use impacts and anthropogenic climate change, including associated species redistributions and invasions. High mountains are warming faster than lower elevations. The number of frost days is declining, glaciers are retreating, and snow is remaining for shorter periods, while CO2 partial pressure is increasing. All of these factors affect the way in which ecosystems prosper or degrade. Thanks to the compression of thermal belts and to topographic ruggedness that favors habitat heterogeneity, mountains have a high diversity of biotic communities and species richness at the landscape level. In tropical to temperature regions, high mountains are biogeographically much like islands. With small habitat areas, species tend to be distributed patchily, with populations evolving independently from those on other isolated summits. Although high mountain areas strongly differ in size, geological age, bedrock, glacial history, solar radiation, precipitation patterns, wind exposure, length of growing season, and biotic features, they are all governed by low-temperature conditions. Combined with their distribution over all climate zones on Earth, mountain habitats and their biota, therefore, represent an excellent natural indicator system for tracing the ecological impacts of global climate change. As temperatures rise, plants and animals migrate upward (and poleward). Plant and animal populations on small, isolated mountains have nowhere to go if climates warm and push them upslope. On the other hand, habitat heterogeneity may buffer against biodiversity losses by providing a multitude of potential refugia for species which become increasingly maladapted to their present habitats. Global-scale approaches to monitor climate and biotic change in high mountains as well as modeling and experimental studies are helping explain the nature of these changes. Such studies have found that species from lower elevations are colonizing habitats on mountain summits at an accelerating pace, with five times faster rates than half a century ago. Further, repeated in situ surveys in permanent plots showed a widespread transformation of alpine plant community assemblages toward more warmth-demanding and/or less cold-adapted species. Concurrently to widespread increases in overall species richness, high-elevation plant species have declined in abundance and frequency. Strongly cold-adapted plant species may directly suffer from warmer and longer growing seasons through weak abilities to adjust respiration rates to warmer conditions. Combined effects of warming and decreasing water availability will amplify detrimental effects of climatic stresses on alpine biota. Many of the dwarf and slow-growing species, however, will be affected when taller and faster-growing species from lower elevations invade and prosper with warming in alpine environments and, thus, threaten to outcompete locally established species. Warming conditions will also encourage land use changes and upward movement of agriculture, while loss of snow is a loss to ski fields and scenic tourism.