The role of sediment supply in the adjustment of channel sinuosity across the Amazon Basin

© 2019 Geological Society of America. Sediment supplies are a fundamental component of alluvial river systems, but the importance of sustained supplies of externally derived sediments for the evolution of meandering planforms remains unclear. Here we demonstrate the importance of sediment supply in enhancing the growth of point bars that influence the rate of sinuosity increase through flow deflections in meander bends. We use an archive of Landsat images of 16 meandering reaches from across the Amazon Basin to show that rivers transporting larger sediment loads increase their sinuosity more rapidly than those carrying smaller loads. Sediment-rich rivers are dominated by downstream-rotating meanders that increase their sinuosity more rapidly than both extensional and upstream-rotating meanders. Downstream-rotating meanders appear to establish larger point bars that expand throughout the meander, in contrast to extensional meanders, which have smaller bars, and upstream rotating meanders, which are characterized by deposition over the bar head. These observations demonstrate that the size and position of point bars within meander bends influences flow routing and thus controls the dominant direction of meander growth. Rivers with low sediment supplies build smaller point bars, which reduces their capacity to increase meander curvature and the resulting sinuosity

Can riparian forest buffers increase yields from oil palm plantations?

Forests on tropical floodplains across Southeast Asia are being converted to oil palm plantations. Preserving natural riparian forest corridors along rivers that pass through oil palm plantations has clear benefits for ecological conservation, but these corridors (also called 'buffers') use land that is potentially economically valuable for agriculture. Here, we examine how riparian forest buffers reduce floodplain land loss by slowing rates of riverbank erosion and lateral channel migration, thus providing the fundamentally geomorphic ecosystem service of 'erosion regulation'. Using satellite imagery, assessments of oil palm plantation productivity, and a simplified numerical model of river channel migration, we estimate the economic value of the ecosystem service that riparian buffers provide by protecting adjacent plantation land from bank erosion. We find that cumulative economic losses from bank erosion are higher in the absence of a forest buffer than when a buffer is left intact. Our exploratory analysis suggests that retaining riparian forest buffers along tropical rivers can enhance the viability of floodplain plantations, particularly over time scales (~decades) commensurate with the lifetime of a typical oil palm plantation. Ecosystem services that stem directly from geomorphic processes could play a vital role in efforts to guide the long‐term environmental sustainability of tropical river systems. Accounting for landscape dynamics in projections of economic returns could help bring palm oil industry goals into closer alignment with environmental conservation efforts

Duplications disrupt chromatin architecture and rewire GPR101-enhancer communication in X-linked acrogigantism

X-linked acrogigantism (X-LAG) is the most severe form of pituitary gigantism and is characterized by aggressive growth hormone (GH)-secreting pituitary tumors that occur in early childhood. X-LAG is associated with chromosome Xq26.3 duplications (the X-LAG locus typically includes VGLL1, CD40LG, ARHGEF6, RBMX, and GPR101) that lead to massive pituitary tumoral expression of GPR101, a novel regulator of GH secretion. The mechanism by which the duplications lead to marked pituitary misexpression of GPR101 alone was previously unclear. Using Hi-C and 4C-seq, we characterized the normal chromatin structure at the X-LAG locus. We showed that GPR101 is located within a topologically associating domain (TAD) delineated by a tissue-invariant border that separates it from centromeric genes and regulatory sequences. Next, using 4C-seq with GPR101, RBMX, and VGLL1 viewpoints, we showed that the duplications in multiple X-LAG-affected individuals led to ectopic interactions that crossed the invariant TAD border, indicating the existence of a similar and consistent mechanism of neo-TAD formation in X-LAG. We then identified several pituitary active cis-regulatory elements (CREs) within the neo-TAD and demonstrated in vitro that one of them significantly enhanced reporter gene expression. At the same time, we showed that the GPR101 promoter permits the incorporation of new regulatory information. Our results indicate that X-LAG is a TADopathy of the endocrine system in which Xq26.3 duplications disrupt the local chromatin architecture forming a neo-TAD. Rewiring GPR101-enhancer interaction within the new regulatory unit is likely to cause the high levels of aberrant expression of GPR101 in pituitary tumors caused by X-LAG.The work was supported by the following funding sources: Fondazione Telethon, Italy grant no. GGP20130 (to G.T.); Society for Endocrinology equipment grant (to G.T.); Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD), National Institutes of Health (NIH) Research project Z01-HD008920 (to C.A.S., supporting G.T., F.R.F.); Fonds d’Investissement pour la Recherche Scientifique (FIRS) of the Centre Hospitalier Universitaire de Liège (to A.F.D. and A.B.); the JABBS Foundation, UK (to A.B.); and Novo Nordisk Belgium Educational Grant, Belgium (to A.F.D. and A.B.). M.F. was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement (#800396) and a Juan de la Cierva-Formación fellowship from the Spanish Ministry of Science and Innovation (FJC2018-038233-I). G.T. was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement (#843843). A.F.D. and D.A. were supported by Action de Recherche Concertée (ARC) Grant 17/21-01 from Liège University. D.A. was supported by grants from Télévie (7461117 F, 7454719 F) and the Léon Fredericq Foundation, Belgium

Assessing changes in global fire regimes

PAGES, Past Global Changes, is funded by the Swiss Academy of Sciences and the Chinese Academy of Sciences and supported in kind by the University of Bern, Switzerland. Financial support was provided by the U.S. National Science Foundation award numbers 1916565, EAR-2011439, and EAR-2012123. Additional support was provided by the Utah Department of Natural Resources Watershed Restoration Initiative. SSS was supported by Brigham Young University Graduate Studies. MS was supported by National Science Centre, Poland (grant no. 2018/31/B/ST10/02498 and 2021/41/B/ST10/00060). JCA was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101026211. PF contributed within the framework of the FCT-funded project no. UIDB/04033/2020. SGAF acknowledges support from Trond Mohn Stiftelse (TMS) and University of Bergen for the startup grant ‘TMS2022STG03’. JMP participation in this research was supported by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). A.-LD acknowledge PAGES, PICS CNRS 06484 project, CNRS-INSU, Région Nouvelle-Aquitaine, University of Bordeaux DRI and INQUA for workshop support.Background The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Peer reviewe

Global wealth disparities drive adherence to COVID-safe pathways in head and neck cancer surgery

Peer reviewe

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Meander cutoff and the controls on the production of oxbow lakes

Using satellite images archived by Google Earth™, we measured channel and oxbow-lake characteristics of 30 large meandering rivers to identify the controls on the production of oxbow lakes by meander cutoff. Cutoff produced lognormal distributions of lake lengths within the studied reaches, and the geometric mean lake length of each population correlated positively and exponentially with sinuosity, due to more highly sinuous reaches being comprised of longer meanders and to cutoff removing longer segments of more sinuous channels. We successfully predicted the size-frequency distributions of lakes stored within the flood-plains of five freely meandering reaches using only channel sinuosity and an assumption of the variance about the geometric mean lake length, a variable that did not significantly vary between the studied reaches. While the river's sinuosity remains steady, the temporal rate of cutoff can be estimated using channel sinuosity, the fraction by which cutoff reduces channel length, and the rate at which the reach lengthens by meander growth

Hulls of ordered algebras: projectability, strong projectability and lateral completeness

There has been compelling evidence during the past decade that lattice-ordered groups (ℓ-groups) play a far more significant role in the study of algebras of logic than it had been previously anticipated. Their key role has emerged on two fronts: First, a number of research articles have established that some of the most prominent classes of algebras of logic may be viewed as ℓ-groups with a modal operator. Second, and perhaps more importantly, recent research has demonstrated that the foundations of the Conrad Program for ℓ-groups can be profitably extended to a much wider class of algebras, namely the variety of e-cyclic residuated lattices – that is, residuated lattices that satisfy the identity x\e≈e/x. Here, the term Conrad Program refers to Paul Conrad's approach to the study of ℓ-groups that analyzes the structure of individual or classes of ℓ-groups by primarily focusing on their lattices of convex ℓ-subgroups. The present article, building on the aforementioned works, studies existence and uniqueness of the laterally complete, projectable and strongly projectable hulls of e-cyclic residuated lattices. While these hulls first made their appearance in the context of functional analysis, and in particular the theory of Riesz spaces, their introduction into the study of algebras of logic adds new tools and techniques in the area and opens up possibilities for a deep exploration of their logical counterparts

A mechanism of chute cutoff along large meandering rivers with uniform floodplain topography

Incidents of chute cutoff are pervasive along many meandering rivers worldwide, but the process is seldom incorporated into theoretical analyses of planform evolution, partly due to the paucity of observations describing its physical controls. Here, we describe a mechanism of chute cutoff that may be prevalent along large meandering rivers with uniform floodplain topography. The mechanism occurs independently of sudden changes in conveyance capacity, such as those caused by natural dams, and instead, it is initiated during a flood by the incision of an embayment. The embayment is typically located almost a channel width upstream of the entrance to the meander that undergoes cutoff, and subsequent floods extend the embayment downstream until a chute is formed. Using sequences of historical aerial photos of the Sacramento River in California, USA, we found that embayments formed where channel curvature was greatest, or where the channel most tightly curved away from the downstream flow path. Embayments formed only within those portions of the floodplain that were lightly vegetated by grasses or crops. We develop a simple physical model that describes the environmental conditions that can lead to embayment formation. The model considers the role of floodplain vegetation in preventing chute incision and in part explains why chute cutoff is prevalent along some meandering rivers but not others

Logging effects on sediment flux observed in a pollen-based record of overbank deposition in a northern California catchment

A palynological approach was used to estimate overbank deposition rates in a forested catchment affected by logging. The palynological approach uses downcore variations in total fossil pollen and fossil pollen assemblage to calculate rates of overbank deposition and has a distinct advantage over radioisotopic approaches in that it is not limited by radioactive decay. Using this approach, we determined that overbank deposition rates increased over 400 per cent within years of logging events and that the increased rates persisted for less than 4 years. After logging-induced deposition peaked, overbank deposition decreased over 60 per cent relative to the pre-logging background values. The decreased deposition rates persisted for over 40 years. The immediate effect of logging in this catchment was to induce mass-wasting events in hollows that produced rapidly travelling sediment pulses. In the subsequent recovery period, reduced sediment loading occurred as a result of a reduction in the volume of sediment available for transport. The reduction in sediment load led to a reduction in overbank deposition rates until subsequent logging disturbances destabilized and emptied other hollows