When rivers turn to deserts and deserts to rivers
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The role of rivers in the origin and future of Amazonian biodiversity
The rich biodiversity of Amazonia is shaped geographically and ecologically by its rivers and their cycles of seasonal flooding. Anthropogenic effects, such as deforestation, infrastructure development and extreme climatic events, threaten the ecological processes sustaining Amazonian ecosystems. In this Review, we explore the coupled evolution of Amazonian rivers and biodiversity associated with terrestrial and seasonally flooded environments, integrating geological, climatic, ecological and genetic evidence. Amazonia and its fluvial environments are highly heterogeneous, and the drainage system is historically dynamic and continually evolving; as a result, the discharge, sediment load and strength of rivers as barriers to biotic dispersal has changed through time. Ecological affinities of taxa, drainage rearrangements and variations in riverine landscape caused by past climate changes have mediated the evolution of the high diversity found in modern-day Amazonia. The connected history of the region’s biodiversity and landscape provides fundamental information for mitigating current and future impacts. However, incomplete knowledge about species taxonomy, distributions, habitat use, ecological interactions and occurrence patterns limits our understanding. Partnerships with Indigenous peoples and local communities, who have close ties to land and natural resources, are key to improving knowledge generation and dissemination, enabling better impact assessments, monitoring and management of the riverine systems at risk from evolving pressures.
Occurrence characteristics and transport processes of riverine microplastics in different connectivity contexts
This study is the first to quantify the migration processes of riverine microplastics under different connectivity contexts based on the spatial variation characteristics of microplastic loads. Microplastics in multidammed, single-dammed, and nondammed rivers are significantly different in three categories: abundance, flux, and inventory. Artificial damming can lead to multicategory reorganization of riverine microplastics, including size, polymer type, shape, and color. Artificial damming has led to the formation of microplastic hotspots in river waters and sediments due to reduced river mobility. Notably, low-velocity regions in non-dammed rivers are high hotspot for microplastic deposition, and their inventories may even be 10.63–12.71 times higher than those of other riverbeds. Additionally, results based on microplastic abundance differ significantly from those based on microplastic loads, which in some cases even showed contradictory results. Therefore, future studies must incorporate microplastic loads into the assessment to enhance our understanding of the fate of microplastics in river systems.
Common loss of far-red light photoacclimation in cyanobacteria from hot and cold deserts: a case study in the Chroococcidiopsidales
Deserts represent an extreme challenge for photosynthetic life. Despite their aridity, they are often inhabited by diverse microscopic communities of cyanobacteria. These organisms are commonly found in lithic habitats, where they are partially sheltered from extremes of temperature and UV radiation. However, living under the rock surface imposes additional constraints, such as limited light availability, and enrichment of longer wavelengths than are typically usable for oxygenic photosynthesis. Some cyanobacteria from the genus Chroococcidiopsis can use this light to photosynthesize, in a process known as far-red light photoacclimation, or FaRLiP. This genus has commonly been reported from both hot and cold deserts. However, not all Chroococcidiopsis strains carry FaRLiP genes, thus motivating our study into the interplay between FaRLiP and extreme lithic environments. The abundance of sequence data and strains provided the necessary material for an in-depth phylogenetic study, involving spectroscopy, microscopy, and determination of pigment composition, as well as gene and genome analyses. Pigment analyses revealed the presence of red-shifted chlorophylls d and f in all FaRLiP strains tested. In addition, eight genus-level taxa were defined within the encompassing Chroococcidiopsidales, clarifying the phylogeny of this long-standing polyphyletic order. FaRLiP is near universally present in a generalist genus identified in a wide variety of environments, Chroococcidiopsis sensu stricto, while it is rare or absent in closely related, extremophile taxa, including those preferentially inhabiting deserts. This likely reflects the evolutionary process of gene loss in specialist lineages.
Successes and failures of conservation actions to halt global river biodiversity loss
To address the losses of river biodiversity worldwide, various conservation actions have been implemented to promote recovery of species and ecosystems. In this Review, we assess the effectiveness of these actions globally and regionally, and identify causes of success and failure. Overall, actions elicit little improvement in river biodiversity, in contrast with reports from terrestrial and marine ecosystems. This lack of improvement does not necessarily indicate a failure of any individual action. Rather, it can be attributed in part to remaining unaddressed stressors driving biodiversity loss; a poor match between the spatial scale of action and the scale of the affected area; and absence of adequate monitoring, including insufficient timescales, missing reference and control sites or insufficient selection of targeted taxa. Furthermore, outcomes are often not reported and are unevenly distributed among actions, regions and organism groups. Expanding from local-scale actions to coordinated, transformative, catchment-scale management approaches shows promise for improving outcomes. Such approaches involve identifying major stressors, appropriate conservation actions and source populations for recolonization, as well as comprehensive monitoring, relevant legislation and engaging all stakeholders to promote the recovery of river biodiversity.
Water industry strategies to manufacture doubt and deflect blame for sewage pollution in England
The water and sewerage companies (WaSCs) in England are majority-owned by a range of global investors. The industry is under intense scrutiny for widespread failure in its environmental performance, discharging 12.7 million monitored hours of untreated wastewater and sewage into English waterways between 2019 and the end of 2023. At the time of writing, multiple investigations by environmental and financial regulators are in progress, and regulatory oversight is under review by the recently formed Office for Environmental Protection. While limited monitoring hid the full extent of underperformance, we argue that the WaSCs have prolonged this environmental disaster through strategies that mirror those of other large polluting industries in the past. We test this hypothesis for the nine major WaSCs in England against a published framework of 28 ‘greenwashing/deception’ tactics of large industries. We identified 22 of these tactics that could be seen as disinformation, greenwashing and manufacturing doubt. The financial exploitation of water resources in England, alongside long-term degradation of infrastructure and ineffective regulation, raises globally important issues around water security, ethics and environmental stewardship. Much greater scrutiny of both industry performance and industry communication is required.
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