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Owing to a long history of anthropogenic pressures, freshwater ecosystems are among the most vulnerable to biodiversity loss1. Mitigation measures, including wastewater treatment and hydromorphological restoration, have aimed to improve environmental quality and foster the recovery of freshwater biodiversity2. Here, using 1,816 time series of freshwater invertebrate communities collected across 22 European countries between 1968 and 2020, we quantified temporal trends in taxonomic and functional diversity and their responses to environmental pressures and gradients. We observed overall increases in taxon richness (0.73% per year), functional richness (2.4% per year) and abundance (1.17% per year). However, these increases primarily occurred before the 2010s, and have since plateaued. Freshwater communities downstream of dams, urban areas and cropland were less likely to experience recovery. Communities at sites with faster rates of warming had fewer gains in taxon richness, functional richness and abundance. Although biodiversity gains in the 1990s and 2000s probably reflect the effectiveness of water-quality improvements and restoration projects, the decelerating trajectory in the 2010s suggests that the current measures offer diminishing returns. Given new and persistent pressures on freshwater ecosystems, including emerging pollutants, climate change and the spread of invasive species, we call for additional mitigation to revive the recovery of freshwater biodiversity.

For more than five decades, research has been conducted at Ny-Ålesund, in Svalbard, Norway, to understand the structure and functioning of High-Arctic ecosystems and the profound impacts on them of environmental change. Terrestrial, freshwater, glacial and marine ecosystems are accessible year-round from Ny-Ålesund, providing unique opportunities for interdisciplinary observational and experimental studies along physical, chemical, hydrological and climatic gradients. Here, we synthesize terrestrial and freshwater research at Ny-Ålesund and review current knowledge of biodiversity patterns, species population dynamics and interactions, ecosystem processes, biogeochemical cycles and anthropogenic impacts. There is now strong evidence of past and ongoing biotic changes caused by climate change, including negative effects on populations of many taxa and impacts of rain-on-snow events across multiple trophic levels. While species-level characteristics and responses are well understood for macro-organisms, major knowledge gaps exist for microbes, invertebrates and ecosystem-level processes. In order to fill current knowledge gaps, we recommend (1) maintaining monitoring efforts, while establishing a long-term ecosystem-based monitoring programme; (2) gaining a mechanistic understanding of environmental change impacts on processes and linkages in food webs; (3) identifying trophic interactions and cascades across ecosystems; and (4) integrating long-term data on microbial, invertebrate and freshwater communities, along with measurements of carbon and nutrient fluxes among soils, atmosphere, freshwaters and the marine environment. The synthesis here shows that the Ny-Ålesund study system has the characteristics needed to fill these gaps in knowledge, thereby enhancing our understanding of High-Arctic ecosystems and their responses to environmental variability and change.

Introduction: Allowing young drivers to gain experience while being supervised by an experienced driver is a widely used measure to try to reduce crash risk. On 1 January 2017, the Danish licensing system was updated to allow licensing at age 17 with post-license supervised driving until solo driving at age 18. Method: Based on data from the Danish Driving License register and Statistics Denmark, including the entire population, the purpose of this study is to determine if sociodemographic characteristics and a history of violations and crash involvement among youth predict licensing at age 17. A second purpose is to estimate the time period from licensing until the driver turns 18 and to explore changes in license demand in the context of Denmark’s updated licensing system. Results: An increasing proportion choose to license at the age of 17, but the proportion below 19 with a driver’s license is unchanged. On average, the license is obtained 5.3 months before turning 18. Living in rural areas, with both parents, and in a family with several cars and higher income increases the likelihood of licensing at age 17. Young people with a history of involvement in non-traffic-related accidents or violations are more likely to license at age 17. Conclusion: Lowering the license age to allow supervised driving increases early licensing. The average time period from licensing until the driver turns 18 is less than six months. Sociodemographic characteristics predict early licensing. Practical implications: Minimum requirements for the time period from licensing until the driver turns 18 are needed to support a safety benefit. Follow-up studies mapping supervised driving, crash involvement, and possible changes in crash risk associated with the change in the Danish licensing system are needed to specify the requirements.

Local biodiversity trends over time are likely to be decoupled from global trends, as local processes may compensate or counteract global change. We analyze 161 long-term biological time series (15–91 years) collected across Europe, using a comprehensive dataset comprising ~6,200 marine, freshwater and terrestrial taxa. We test whether (i) local long-term biodiversity trends are consistent among biogeoregions, realms and taxonomic groups, and (ii) changes in biodiversity correlate with regional climate and local conditions. Our results reveal that local trends of abundance, richness and diversity differ among biogeoregions, realms and taxonomic groups, demonstrating that biodiversity changes at local scale are often complex and cannot be easily generalized. However, we find increases in richness and abundance with increasing temperature and naturalness as well as a clear spatial pattern in changes in community composition (i.e. temporal taxonomic turnover) in most biogeoregions of Northern and Eastern Europe.

1. Herbivorous zooplankton maintain a rather constant elemental composition in their body mass as compared with the variability commonly encountered in their food. Furthermore, their high phosphorus (P) and nitrogen (N) content means that they often face an excess of carbon (C) in their diet. Regulation of this surplus of energy may occur via modulation of assimilation efficiency, or postassimilation by increased respiration (CO2) and/or excretion dissolved organic carbon, DOC. Whereas several studies have examined the effect of elemental imbalance in the genus Daphnia, few have examined other zooplankton taxa. 2. We investigated whether the rotifer Brachionus calyciflorus uses increased respiration as a means of stoichiometrically regulating excess dietary C. Growth rate and respiration were measured under different food qualities (C : N and C : P ratios). 3. Both C : N and C : P ratios in food had strong effects on growth rate, demonstrating strong nutrient limitation of rotifer growth when nutrient elements were depleted in the diet and indicating the need for stoichiometric regulation of excess ingested C. 4. Respiration measurements, supported by a stoichiometric model, indicated that excess C was not released as CO2 in B. calyciflorus and that nutrient balance must therefore be maintained by other means such as excretion of DOC or egestion in faecal material.

1. Herbivorous zooplankton face considerable temporal and spatial variation in food quality, to which they respond by adapting their life histories. Zooplankton may even take up mineral nutrients directly, and use these to counter the effects of algal nutrient limitation (mineral compensation). This study examined the life history of the rotifer Brachionus calyciflorus fed phosphorus-, and nitrogen-limited Scenedesmus obliquus (Chlorophyta), and investigated whether B. calyciflorus was capable of mineral compensation. 2. Both phosphorus- and nitrogen-limited algae gave similar life history responses: somatic growth and reproduction were reduced, whereas lifespan remained unaffected. 3. No evidence was found for mineral compensation in B. calyciflorus in relation to detrimental life history effects, so mineral compensation does not seem to be relevant for this species under field conditions. 4. The similarity in life history responses of B. calyciflorus and the low levels of -3 PUFAs in both phosphorus- and nitrogen-depleted algae suggest that -3 PUFAs were limiting to B. calyciflorus, although other (bio)chemicals or mineral nutrients may also have been important. 5. No trade-off was observed between life span and reproduction during algal nutrient limitation. Reduced population growth rates of B. calyciflorus were caused by shorter reproductive periods. [KEYWORDS: food quality growth reproduction Scenedesmus obliquus stoichiometry], 1. Herbivorous zooplankton face considerable temporal and spatial variation in food quality, to which they respond by adapting their life histories. Zooplankton may even take up mineral nutrients directly, and use these to counter the effects of algal nutrient limitation (mineral compensation). This study examined the life history of the rotifer Brachionus calyciflorus fed phosphorus-, and nitrogen-limited Scenedesmus obliquus (Chlorophyta), and investigated whether B. calyciflorus was capable of mineral compensation. 2. Both phosphorus- and nitrogen-limited algae gave similar life history responses: somatic growth and reproduction were reduced, whereas lifespan remained unaffected. 3. No evidence was found for mineral compensation in B. calyciflorus in relation to detrimental life history effects, so mineral compensation does not seem to be relevant for this species under field conditions. 4. The similarity in life history responses of B. calyciflorus and the low levels of -3 PUFAs in both phosphorus- and nitrogen-depleted algae suggest that -3 PUFAs were limiting to B. calyciflorus, although other (bio)chemicals or mineral nutrients may also have been important. 5. No trade-off was observed between life span and reproduction during algal nutrient limitation. Reduced population growth rates of B. calyciflorus were caused by shorter reproductive periods. [KEYWORDS: food quality growth reproduction Scenedesmus obliquus stoichiometry]