Aquatic ecosystems are under severe pressure. Human activities introduce an array of pressures that impact ecosystems and their components. In this study we focus on the aquatic domains of fresh, coastal and marine waters, including rivers, lakes and riparian habitats to transitional, coastal as well as shelf and oceanic habitats. In an environmental risk assessment approach, we identified impact chains that link 45 human activities through 31 pressures to 82 ecosystem components. In this linkage framework >22,000 activity-pressure-ecosystem component interactions were found across seven European case studies. We identified the environmental impact risk posed by each impact chain by first categorically weighting the interactions according to five criteria: spatial extent, dispersal potential, frequency of interaction, persistence of pressure and severity of the interaction, where extent, dispersal, frequency and persistence account for the exposure to risk (spatial and temporal), and the severity accounts for the consequence of the risk. After assigning a numerical score to each risk criterion, we came up with an overall environmental impact risk score for each impact chain. This risk score was analysed in terms of (1) the activities and pressures that introduce the greatest risk to European aquatic domains, and (2) the aquatic ecosystem components and realms that are at greatest risk from human activities. Activities related to energy production were relevant across the aquatic domains. Fishing was highly relevant in marine and environmental engineering in fresh waters. Chemical and physical pressures introduced the greatest risk to the aquatic realms. Ecosystem components that can be seen as ecotones between different ecosystems had high impact risk. We show how this information can be used in informing management on trade-offs in freshwater, coastal and marine resource use and aid decision-making.

Large river-floodplain systems are hotspots of biodiversity and ecosystem services but are also used for multiple human activities, making them one of the most threatened ecosystems worldwide. There is wide evidence that reconnecting river channels with their floodplains is an effective measure to increase their multi-functionality, i.e., ecological integrity, habitats for multiple species and the multiple functions and services of river-floodplain systems, although, the selection of promising sites for restoration projects can be a demanding task. In the case of the Danube River in Europe, planning and implementation of restoration projects is substantially hampered by the complexity and heterogeneity of the environmental problems, lack of data and strong differences in socio-economic conditions as well as inconsistencies in legislation related to river management. We take a quantitative approach based on best-available data to assess biodiversity using selected species and three ecosystem services (flood regulation, crop pollination, and recreation), focused on the navigable main stem of the Danube River and its floodplains. We spatially prioritize river-floodplain segments for conservation and restoration based on (1) multi-functionality related to biodiversity and ecosystem services, (2) availability of remaining semi-natural areas and (3) reversibility as it relates to multiple human activities (e.g. flood protection, hydropower and navigation). Our approach can thus serve as a strategic planning tool for the Danube and provide a method for similar analyses in other large river-floodplain systems.

The capacity of ecosystems to supply ecosystem services is decreasing. Sustaining this supply requires an understanding of the links between the impacts of pressures introduced by human activities and how this can lead to changes in the supply of services. Here, we apply a novel approach, assessing 'risk to ecosystem service supply' (RESS), across a range of aquatic ecosystems in seven case studies. We link aggregate impact risk from human activities on ecosystem components, with a relative score of their potential to supply services. The greatest RESS is found where an ecosystem component with a high potential to supply services is subject to high impact risk. In this context, we explore variability in RESS across 99 types of aquatic ecosystem component from 11 realms, ranging from oceanic to wetlands. We explore some causes of variability in the RESS observed, including assessment area, Gross Domestic Product (GDP) and population density. We found that Lakes, Rivers, Inlets and Coastal realms had some of the highest RESS, though this was highly dependent on location. We found a positive relationship between impact risk and service supply potential, indicating the ecosystem components we rely on most for services, are also those most at risk. However, variability in this relationship indicates that protecting the supply of ecosystem services alone will not protect all parts of the ecosystem at high risk. Broad socio-economic factors explained some of the variability found in RESS. For example, RESS was positively associated with GDP and artificial and agricultural land use in most realms, highlighting the need to achieve balance between increasing GDP and sustaining ecosystem health and human wellbeing more broadly. This approach can be used for sustainable management of ecosystem service use, to highlight the ecosystem components most critical to supplying services, and those most at risk.

Aim: Systematic conservation planning is vital for allocating protected areas given the spatial distribution of conservation features, such as species. Due to incomplete species inventories, species distribution models (SDMs) are often used for predicting species’ habitat suitability and species’ probability of occurrence. Currently, SDMs mostly ignore spatial dependencies in species and predictor data. Here, we provide a comparative evaluation of how accounting for spatial dependencies, that is, autocorrelation, affects the delineation of optimized protected areas.Location: Southeast Australia, Southeast U.S. Continental Shelf, Danube River Basin.Methods: We employ Bayesian spatially explicit and non‐spatial SDMs for terrestrial, marine and freshwater species, using realm‐specific planning unit shapes (grid, hexagon and subcatchment, respectively). We then apply the softwaregurobito optimize conservation plans based on species targets derived from spatial and non‐spatial SDMs (10%–50% each to analyse sensitivity), and compare the delineation of the plans.Results: Across realms and irrespective of the planning unit shape, spatially explicit SDMs (a) produce on average more accurate predictions in terms of AUC, TSS, sensitivity and specificity, along with a higher species detection probability. All spatial optimizations meet the species conservation targets. Spatial conservation plans that use predictions from spatially explicit SDMs (b) are spatially substantially different compared to those that use non‐spatial SDM predictions, but (c) encompass a similar amount of planning units. The overlap in the selection of planning units is smallest for conservation plans based on the lowest targets and vice versa.Main conclusions: Species distribution models are core tools in conservation planning. Not surprisingly, accounting for the spatial characteristics in SDMs has drastic impacts on the delineation of optimized conservation plans. We therefore encourage practitioners to consider spatial dependencies in conservation features to improve the spatial representation of future protected areas.

The EU Nature Restoration Law represents an important opportunity for freshwater habitat restoration and, consequently, freshwater biodiversity protection. However, a number of challenges must be anticipated in its implementation, which may compromise its success. Some aspects, particularly those relating to freshwater ecosystems, require more clarification. We use riverine ecosystems to illustrate existing ambiguities in the proposed legislation and the potential consequences of leaving these aspects open to interpretation during the implementation process. We also discuss potential solutions to these problems which could help ensure that the law's objectives are met. We argue that river network structure and connectivity dimensions, which result into river meta‐ecosystems, must be explicitly considered. For that purpose, we ask for clear definitions of the critical terms “free‐flowing rivers,” “barriers,” and “reference areas.” In addition, we recommend developing methods for integrated assessment of connectivity across river networks. As a key property of river ecosystems, this must be used to prioritize actions to increase the length and number of free‐flowing rivers. Adequate restoration planning at larger spatial scales will benefit from a meta‐ecosystem perspective and accurate representation of aquatic‐terrestrial linkages, which will significantly improve the efficacy of restoration efforts. Furthermore, stakeholder and citizen engagement offer important opportunities at local, national, and European scales, and should be fostered to ensure inclusive decision‐making. The conservation challenges outlined here are particularly important for rivers, but they also have implications for other ecosystems. These considerations are useful for policymakers, conservationists, and other stakeholders involved in the Nature Restoration Law and related policy initiatives.This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness Human Water > Water Governance