Inland navigation and land use interact to impact European freshwater biodiversity.

Inland navigation in Europe is proposed to increase in the coming years, being promoted as a low-carbon form of transport. However, we currently lack knowledge on how this would impact biodiversity at large scales and interact with existing stressors. Here we addressed this knowledge gap by analysing fish and macroinvertebrate community time series across large European rivers comprising 19,592 observations from 4,049 sampling sites spanning the past 32 years. We found ship traffic to be associated with biodiversity declines, that is, loss of fish and macroinvertebrate taxonomic richness, diversity and trait richness. Ship traffic was also associated with increases in taxonomic evenness, which, in concert with richness decreases, was attributed to losses in rare taxa. Ship traffic was especially harmful for benthic taxa and those preferring slow flows. These effects often depended on local land use and riparian degradation. In fish, negative impacts of shipping were highest in urban and agricultural landscapes. Regarding navigation infrastructure, the negative impact of channelization on macroinvertebrates was evident only when riparian degradation was also high. Our results demonstrate the risk of increasing inland navigation on freshwater biodiversity. Integrative waterway management accounting for riparian habitats and landscape characteristics could help to mitigate these impacts.

Low parasite infestations in high densities: The paradox of woodpigeons in urban areas.

The type of habitat occupied by avian populations has a marked effect on the parasitises they host. The growth of cities and urban areas in recent decades has favoured some species of birds adapted to these types of habitats - urban exploiters - although the effects of urbanisation on the parasitism of wildlife are not always well known. This study compares the ectoparasites characteristic of two differentiated populations of woodpigeons, one located in a predominantly urban environment and the other in a rural one. Most of the species found were chewing lice, with Columbicola claviformis and Campanulotes bidentatus being dominant. Despite the higher density of the urban population, woodpigeon individuals were characterised by a lower abundance of chewing lice, as well as the presence of ectoparasites typical of feral pigeons such as Hohorstiella lata and the hippoboscids fly, Pseudolynchia canariensis. Similarly, birds with lower weights showed a higher parasitic load, which became more noticeable in urban woodpigeons. The lower ectoparasite load of urban hosts represents a health advantage compared with rural populations, which could be one of the causes of greater growth and reproductive success in urban populations of woodpigeons.

Improving river hydromorphological assessment through better integration of riparian vegetation: Scientific evidence and guidelines.

River hydromorphology has long been subjected to huge anthropogenic pressures with severe negative impacts on related ecosystems' functioning and water quality. Therefore, improving river hydromorphological conditions represents a priority task in sustainable river management and requires proper assessment tools. It is well known that riparian vegetation plays a crucial role in sustaining river hydromorphological conditions. However, it has been nearly neglected in most hydromorphological assessment protocols, including the European Water Framework Directive (WFD). This paper reviews and synthesizes the relevance of riparian vegetation for river hydromorphology, focusing on its contribution to streamflow and sediment regime conditions. We also examine how riparian vegetation is considered in the WFD and how it is included in national hydromorphological protocols currently in use. Our findings point to a temporal mismatch between the date when the WFD came into force and the emergence of scientific and technologic advances in riparian vegetation dynamism and bio-geomorphic modeling. To overcome this misalignment, we present promising approaches for the characterization and assessment of riparian vegetation, which include the identification of vegetation units and indicators at multiple scales to support management and restoration measures. We discuss the complexity of riparian vegetation assessment, particularly with respect to the establishment of river-type-based reference conditions and the monitoring and management targets, and propose some attributes that can serve as novel indicators of the naturalness vs. artificiality of riparian vegetation. We argue that the hydromorphological context of the WFD should be revisited and offer guidance to integrate riparian vegetation in river hydromorphological monitoring and assessment.

Geomorphological evolution along international riverine borders: The flow of the Aras River through Iran, Azerbaijan, and Armenia.

International rivers are one of the most politicized natural resources. Their dynamism, whether driven by the influence of natural processes or artificial drivers, can generate political issues between countries where de river is the common boundary. The present study has tried to discern the role of international riverine borders as a limiting factor of their dynamics from a geomorphological point of view. In this context, the main objective of this research is to assess how land cover in the floodplain has been affected by river dynamics along a border by analysing a 160-km-long reach of the Aras River, which is the natural frontier between Iran, Azerbaijan, and Armenia, over the last 35 years (i.e., 1984-2019). Landsat images from 1984 to 2019 have been used to assess land cover changes in a floodplain buffer using Support Vector Machine algorithms and geomorphological changes through indexes such as the River Network Change Index, Channel Mobility Index, Sinuosity index, and Bank retreat index. The results show that active channel has mainly experienced a narrowing process during the study period, with a narrowing rate of 2.05 m/year. In addition, the average value of the River Network Channel Index (-2.45 m/year) reveals that lateral deposition and narrowing were the main processes occurring within the study reach. Channel displacement toward the non-Iranian part was more prominent, being around 27 m on average along the whole study reach which may cause new problems and conflicts that conditions the border situation. In the whole study period, the succession category showed a higher rate of increase in comparison with rejuvenation. Stabilization of surfaces prevailed, with most of the area maintaining the same type during the study period. Regarding land cover types, artificialization appears to be the most prominent transition that express the Aras River, and specifically the floodplain buffer zone, has been strongly affected by human pressure, with farmland activities, urbanization, and damming being the most important types. The key to this habitat degradation comes from the management with irrigation purposes of large reservoirs that directly or indirectly would cause most of the changes detected.

Regeneration of Salicaceae riparian forests in the Northern Hemisphere: A new framework and management tool.

Human activities on floodplains have severely disrupted the regeneration of foundation riparian shrub and tree species of the Salicaceae family (Populus and Salix spp.) throughout the Northern Hemisphere. Restoration ecologists initially tackled this problem from a terrestrial perspective that emphasized planting. More recently, floodplain restoration activities have embraced an aquatic perspective, inspired by the expanding practice of managing river flows to improve river health (environmental flows). However, riparian Salicaceae species occupy floodplain and riparian areas, which lie at the interface of both terrestrial and aquatic ecosystems along watercourses. Thus, their regeneration depends on a complex interaction of hydrologic and geomorphic processes that have shaped key life-cycle requirements for seedling establishment. Ultimately, restoration needs to integrate these concepts to succeed. However, while regeneration of Salicaceae is now reasonably well-understood, the literature reporting restoration actions on Salicaceae regeneration is sparse, and a specific theoretical framework is still missing. Here, we have reviewed 105 peer-reviewed published experiences in restoration of Salicaceae forests, including 91 projects in 10 world regions, to construct a decision tree to inform restoration planning through explicit links between the well-studied biophysical requirements of Salicaceae regeneration and 17 specific restoration actions, the most popular being planting (in 55% of the projects), land contouring (30%), removal of competing vegetation (30%), site selection (26%), and irrigation (24%). We also identified research gaps related to Salicaceae forest restoration and discuss alternative, innovative and feasible approaches that incorporate the human component.