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In this contribution we quantify the potential to reduce the discharge of excess nutrients with European wastewater, by modelling pollution, greenhouse gas emissions and the costs of measures under various scenarios. We analyse two types of strategies, namely extending the requirement of nutrient removal to broader areas and increasing the removal efficiency of nitrogen and phosphorus. As the former strategy usually entails some infrastructural investment while the latter entails an optimization of the existing processes, the two imply different costs, and increasing efficiency usually shows a better cost–benefit ratio. In any case, actions increasing nutrient removal are expected to pay for themselves in terms of the benefits they bring in abating water pollution and (for nitrogen) greenhouse gas emissions. Nitrogen removal becomes even more attractive whenever the infrastructural investments that we assume may be avoided, thanks to the possibility of an optimized use of the existing infrastructure. Phosphorus removal may become even more attractive with the progress of technologies for its recovery from wastewater and sludge, and with the increase of its demand for fertilizers and other industrial uses. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probability of river impacts occurrences were estimated from pressure indicators. • Good ecological status failure, nutrient and organic pollution were well predicted. • Probability to fail achieving good ecological status was >60% in 36% of river length. • Hydro-morphological alteration mapping requires specific water pressure indicators. • The maps of impact occurrence probability are useful for river basin management. Understanding how anthropogenic pressures affect river ecological status is pivotal to designing effective management strategies. Knowledge on river aquatic habitats status in Europe has increased tremendously since the introduction of the European Union Water Framework Directive, yet heterogeneities in mandatory monitoring and reporting still limit identification of patterns at continental scale. Concurrently, several model and data-based indicators of anthropogenic pressures to freshwater that cover the continent consistently have been developed. The objective of this work was to create European maps of the probability of occurrence of river conditions, namely failure to achieve good ecological status, or to be affected by specific pervasive impacts. To this end, we applied logistic regression methods to model the river conditions as functions of continental-scale water pressure indicators. The prediction capacity of the models varied with river condition: the probability to fail achieving good ecological status, and occurrence of nutrient and organic pollution were rather well predicted; conversely, chemical (other than nutrient and organic) pollution and alteration of habitats due to hydrological or morphological changes were poorly predicted. The most important indicators explaining river conditions were the shares of agricultural and artificial land, mean annual net abstractions, share of pollution loads from point sources, and the share of upstream river length uninterrupted by barriers. The probability of failing to achieve good ecological status was estimated to be high (>60%) for 36% of the considered river network of about 1.6 M km. Occurrence of impact of nutrient pollution was estimated high (>60%) in 26% of river length and that of organic pollution 20%. The maps are built upon information reported at country level pursuant EU legal obligations, as well as indicators generated from European scale models and data: both sources are affected by epistemic uncertainty. In particular, reported information depend on data collection scoping and schemes, as well as national knowledge and interpretation of river system pressures. In turn, water pressure indicators are affected by heterogeneous biases due to incomplete or incorrect inputs and uncertainty of models adopted. Lack of effective reach- and site-scale indicators may hamper detection of locally relevant impacts, for example in explaining alteration of habitats due to morphological changes. The probability maps provide a continental snapshot of current river conditions, and offer an alternative source of information on river aquatic habitats, which may help filling in knowledge gaps. Foremost, the analysis demonstrates the need for developing more effective continental-scale indicators for hydromorphological alterations and chemical pollution. [ABSTRACT FROM AUTHOR]

Soil erosion is generally recognized as the dominant process of land degradation. The formation and expansion of gullies is often a highly significant process of soil erosion. However, our ability to assess and simulate gully erosion and its impacts remains very limited. This is especially so at regional to continental scales. As a result, gullying is often overlooked in policies and land and catchment management strategies. Nevertheless, significant progress has been made over the past decades. Based on a review of >590 scientific articles and policy documents, we provide a state-of-the-art on our ability to monitor, model and manage gully erosion at regional to continental scales. In this review we discuss the relevance and need of assessing gully erosion at regional to continental scales (Section 1); current methods to monitor gully erosion as well as pitfalls and opportunities to apply them at larger scales (section 2); field-based gully erosion research conducted in Europe and European Russia (section 3); model approaches to simulate gully erosion and its contribution to catchment sediment yields at large scales (section 4); data products that can be used for such simulations (section 5); and currently existing policy tools and needs to address the problem of gully erosion (section 6). Section 7 formulates a series of recommendations for further research and policy development, based on this review. While several of these sections have a strong focus on Europe, most of our findings and recommendations are of global significance. [ABSTRACT FROM AUTHOR]

Animals, plants, and other organisms unintentionally or deliberately brought into a natural environment where they are not normally found, and where they cause harmful effects on that environment, are known also as invasive alien species (IAS). They represent a major threat to native biodiversity and ecosystem functioning, and can affect negatively human health and the economy. We assessed the presence and potential pressure by IAS on terrestrial and freshwater ecosystems across 27 European countries, for 66 IAS of policy concern. We computed a spatial indicator that accounts for the number of IAS present in an area and the extent of the ecosystems affected; for each ecosystem, we also looked at the pattern of invasions in the different biogeographical regions. We found disproportionally greater invasion in the Atlantic region, followed by Continental and Mediterranean regions, possibly related to historical patterns of first introductions. Urban and freshwater ecosystems were the most invaded (nearly 68% and ca. 52% of their extent respectively), followed by forest and woodland (nearly 44%). The average potential pressure of IAS was greater across cropland and forests, where we also found the lowest coefficient of variation. This assessment can be repeated over time to derive trends and monitor progress towards environmental policy objectives., (© 2023. © European Union, under exclusive licence to Springer Nature Limited.)

We have quantified inputs and fate of nutrients in European fresh and marine waters from 1990 to 2018. We have used the conceptual model GREEN to assess the impact of efforts on curbing nutrient pollution in European regions. In the first two decades, i.e. in the 1990s and through the start of the new millennium, nutrient inputs to waters decreased significantly. Nutrient pollution in freshwaters and to the sea largely reduced in all regions, although at different pace. However, around 2008-2010 trends in nutrient inputs changed, marking an increase in the last decade, particularly from agricultural diffuse sources. In some regions, current nutrient inputs to waters are close to those estimated at the beginning of the 1990s. At the end of the study period, nutrient concentrations in freshwaters remain above thresholds congruent with good ecological status of water bodies in most downstream reaches. European policies tackling point sources are close to reach their maximum impact. In the face of this approaching ceiling, sustainable nutrient management on agricultural land becomes pivotal for effective nutrient control in river basins. The regional approach highlighted differences across Europe that may provide tailored opportunities to plan effective strategies for achieving environmental targets., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Invasive alien species (IAS) induce changes to community structure and functions which lead to a decline of endemic species and major irreversible changes to the local physical habitat. The distribution and the impacts of multiple freshwater IAS are not well known, and they have not been investigated simultaneously at catchment and at European scales. This study provides an assessment of the distribution and cumulative impact of freshwater IAS over European catchments. IAS occurrences were retrieved from the European Alien Species Information Network geospatial dataset and updated with the most recent records from the literature. The Cumulative Impact Index of Invasive Alien Species (CIMPAL) was derived by aggregating the impacts of species and their occupied area at catchment level by following three steps: i) IAS were scored by both the magnitude of impacts on freshwater ecosystems and the strength of evidence in the literature, ii) scores were mapped over the catchment area, and iii) scores were summed across IAS over the catchment. The distribution of CIMPAL in the river ecological classes of the Water Framework Directive was examined and increasing/decreasing patterns identified across ecological statuses. Results showed strong spatial variation in the documented distribution and impacts of IAS in Europe. Catchments with CIMPAL scores >40 (range 0-55) clustered in Western European countries (e.g. Belgium and France) were characterised by plant, invertebrate and vertebrate IAS that had both a large impact in magnitude and colonisation at local (catchment level) and large scale (across catchments). CIMPAL showed statistically significant and increasing values from high to bad ecological classes in eight countries only (Belgium, the Czech Republic, Germany, France, Hungary, Italy, Luxemburg, Poland). This study provides comprehensive evidence of the distribution and impact of IAS within freshwater environments that could be used to improve understanding of the ecological pressures at catchment scale., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Biochemical Oxygen Demand (BOD) is an indicator of organic pollution in freshwater bodies correlated to microbiological contamination. High BOD concentrations reduce oxygen availability, degrade aquatic habitats and biodiversity, and impair water use. High BOD loadings to freshwater systems are mainly coming from anthropogenic sources, comprising domestic and livestock waste, industrial emissions, and combined sewer overflows. We developed a conceptual model (GREEN + ) to assess mean annual current organic pollution (BOD fluxes) across Europe. The model was informed with the latest available European datasets of domestic and industrial emissions, population and livestock densities. Model parameters were calibrated using 2008-2012 mean annual BOD concentrations measured in 2157 European monitoring stations, and validated with other 1134 stations. The most sensitive model parameters were abatement of BOD by secondary treatment and the BOD decay exponent of travel time. The mean BOD concentrations measured in monitored stations was 2.10 mg O BOD ) to assess mean annual current organic pollution (BOD fluxes) across Europe. The model was informed with the latest available European datasets of domestic and industrial emissions, population and livestock densities. Model parameters were calibrated using 2008-2012 mean annual BOD concentrations measured in 2157 European monitoring stations, and validated with other 1134 stations. The most sensitive model parameters were abatement of BOD by secondary treatment and the BOD decay exponent of travel time. The mean BOD concentrations measured in monitored stations was 2.10 mg O 2 /L and predicted concentrations were 2.54 mg O 2 /L; the 90th percentile of monitored BOD concentration was 3.51 mg O 2 /L. The model could correctly classify reaches for BOD concentrations classes, from high to poor quality, in 69% of cases. High overestimations (incorrect classification by 2 or more classes) were 2% and large underestimations were 5% of cases. Across Europe about 12% of freshwater network was estimated to be failing good quality due to excessive BOD concentrations (>5 mg O 2 /L. The model could correctly classify reaches for BOD concentrations classes, from high to poor quality, in 69% of cases. High overestimations (incorrect classification by 2 or more classes) were 2% and large underestimations were 5% of cases. Across Europe about 12% of freshwater network was estimated to be failing good quality due to excessive BOD concentrations (>5 mg O 2 /L). Dominant sources of BOD to freshwaters and seas were point sources and emissions from intensive livestock systems. Comparison with previous assessments confirms a decline of BOD pollution since the introduction of EU legislation regulating water pollution., (Copyright © 2019 The Authors. Published by Elsevier B.V. All rights reserved.)