Signal crayfish burrowing, bank retreat and sediment supply to rivers: A biophysical sediment budget

Burrowing into riverbanks by animals transfers sediment directly into river channels and has been hypothesised to accelerate bank erosion and promote mass failure. A field monitoring study on two UK rivers invaded by signal crayfish (Pacifastacus leniusculus) assessed the impact of burrowing on bank erosion processes. Erosion pins were installed in 17 riverbanks across a gradient of crayfish burrow densities and monitored for 22 months. Bank retreat increased significantly with crayfish burrow density. At the bank scale (<6 m river length), high crayfish burrow densities were associated with accelerated bank retreat of up to 253% and more than a doubling of the area of bank collapse compared with banks without burrows. Direct sediment supply by burrowing activity contributed 0.2% and 0.6% of total sediment at the reach (1.1 km) and local bank (<6 m) scales. However, accelerated bank retreat caused by burrows contributed 12.2% and 29.8% of the total sediment supply at the reach and bank scales. Together, burrowing and the associated acceleration of retreat and collapse supplied an additional 25.4 t km−1 a−1 of floodplain sediments at one site, demonstrating the substantial impact that signal crayfish can have on fine sediment supply. For the first time, an empirical relation linking animal burrow characteristics to riverbank retreat is presented. The study adds to a small number of sediment budget studies that compare sediment fluxes driven by biotic and abiotic energy but is unique in isolating and measuring the substantial interactive effect of the acceleration of abiotic bank erosion facilitated by biotic activity. Biotic energy expended through burrowing represents an energy surcharge to the river system that can augment sediment erosion by geophysical mechanisms

Analysis of costs and benefits of restoration-based hazardous fuel reduction, treatments vs. no treatment: Progress report #1 June 13, 2003.

This progress report presents preliminary results of an economic analysis comparing restoration-based fuel treatments to no treatments for areas identified at high risk for fire. The with and without treatment comparison focuses on ponderosa pine and dry mixed conifer forest ecosystems in New Mexico and Arizona. The analysis provides a conservative estimate of the potential economic losses due to no action. The results for New Mexico and Arizona indicate that restoration-based fuel treatments represent a rational economic choice even if one only considers direct avoided cost of current fires suppression activities. Society could pay up to (dollars)505 dollars per acre to treat the areas of high risk, and still break even in terms of investment. This investment cost is net of any value recovered from the restoration treatment; for example if the thinning part of a restoration treatment generated (dollars)200 per acre, the total break-even investment value rises to (dollars)700/acre. This investment break-even value does not include consideration of property damage and associated losses or lost ecosystem values, such as endangered species habitat and recreation amenity values

Diversity, Challenges and Opportunities in the Greater Horn of Africa

Conference Paper No.

The long-term dynamics of invasive signal crayfish forcing of fluvial sediment supply via riverbank burrowing

Animals are important drivers of sediment dynamics. Invasive signal crayfish (Pacifastacus leniusculus) have been shown to supply sediment to rivers by burrowing into riverbanks. Burrowing directly transfers excavated sediment into the river and also has an additional indirect affect by promoting riverbank failure. While previous research has isolated burrow densities at a point in time, rates of burrow construction and of burrow loss due to erosion are unknown, which introduces uncertainty into estimates of how much sediment burrows contribute to rivers. Here we report results from a 5-year study that evaluated the temporal dynamics of crayfish populations, rates of burrow loss due to erosion, and the mass of sediment directly supplied to rivers by burrow excavation. At ten reaches across five lowland streams in England, we estimated the mass of sediment displaced by 1861 new and previously constructed burrows. Both crayfish and burrow densities were variable over time, suggesting that burrows contribute temporally variable amounts of fine sediment to riverine systems. 42 % of observed burrows were constructed within the previous 365 days, and individual burrows lasted on average 461 days. Applying this to comparable historical data, an average of 2.0 t km−1 a−1 of sediment was excavated to construct burrows in the study reaches, which is eight times more than estimated in previous studies. Whilst total burrow densities in each year were not consistently correlated with contemporary crayfish densities, the mass of sediment excavated over the prior year was strongly correlated with contemporary crayfish densities. Current fine sediment management practices are largely aimed at controlling fine sediment delivery, predominately from agricultural activities, but biotic burrowing into riverbanks may represent an important and overlooked source of fine sediment supply. Incorporation of biotic processes in sediment dynamics would improve the accuracy of fluvial sediment budgets and enhance the knowledge base underpinning effective fine-sediment management practices

Disrupted-in-schizophrenia-1 is essential for normal hypothalamic-pituitary-interrenal (HPI) axis function

Psychiatric disorders arise due to an interplay of genetic and environmental factors, including stress. Studies in rodents have shown that mutants for Disrupted-In-Schizophrenia-1 (DISC1), a well-accepted genetic risk factor for mental illness, display abnormal behaviours in response to stress, but the mechanisms through which DISC1 affects stress responses remain poorly understood. Using two lines of zebrafish homozygous mutant for disc1, we investigated behaviour and functioning of the hypothalamic-pituitary-interrenal (HPI) axis, the fish equivalent of the hypothalamic-pituitary-adrenal (HPA) axis. Here, we show that the role of DISC1 in stress responses is evolutionarily conserved and that DISC1 is essential for normal functioning of the HPI axis. Adult zebrafish homozygous mutant for disc1 show aberrant behavioural responses to stress. Our studies reveal that in the embryo, disc1 is expressed in neural progenitor cells of the hypothalamus, a conserved region of the vertebrate brain that centrally controls responses to environmental stressors. In disc1 mutant embryos, proliferating rx3þ hypothalamic progenitors are not maintained normally and neuronal differentiation is compromised: rx3-derived ff1bþ neurons, implicated in anxiety-related behaviours, and corticotrophin releasing hormone (crh) neurons, key regulators of the stress axis, develop abnormally, and rx3-derived pomcþ neurons are disorganised. Abnormal hypothalamic development is associated with dysfunctional behavioural and neuroendocrine stress responses. In contrast to wild type siblings, disc1 mutant larvae show altered crh levels, fail to upregulate cortisol levels when under stress and do not modulate shoal cohesion, indicative of abnormal social behaviour. These data indicate that disc1 is essential for normal development of the hypothalamus and for the correct functioning of the HPA/HPI axis

Infrared monitoring of OH/IR stars near the Galactic Center

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

Do return to work interventions for workers with disabilities and health conditions achieve employment outcomes and are they cost effective? A systematic narrative review

Purpose The purpose of this paper is to evaluate existing evidence on whether return to work interventions achieve employment outcomes and are cost effective in order to better inform those needing accommodations at work, as well as their line managers and trade union representatives, occupational health specialists and HR managers. Design/methodology/approach The paper uses a systematic narrative review to evaluate the evidence on the employment outcomes and cost effectiveness of return to work initiatives. Findings Evidence on interventions for musculoskeletal conditions such as lower back pain indicates that certain forms of intervention such as vocational rehabilitation and workplace-based rehabilitation facilitate outcomes such as employment, reduced sick leave and effective return to work. However, there is very little evidence on whether these interventions are cost effective. More generally there are glaring gaps in evidence on cardio-respiratory (heart and breathing) and mental health conditions with regard to both employment outcomes and the cost of interventions. Research limitations/implications This systematic review has critical and timely implications for both knowledge development and practice. While highlighting methodological limitations in the existing research base, it also presents avenues for further research on return work strategies and the factors inhibiting and facilitating their adoption and effective operation. Originality/value Although there is much existent literature on the return to work process, far less attention has been paid to the employment outcomes and cost effectiveness of interventions. This paper highlights the interventions for musculoskeletal conditions such as lower back conditions that may result in positive employment outcomes, with implications for practice. However, it also highlights gaps in evidence on the employment outcomes and cost effectiveness of interventions for cardio-respiratory (heart and breathing) and mental health conditions.Full Tex

Reconfiguration and regulation of supply chains and HRM in times of economic crisis

This chapter reviews existing evidence on the reconfiguration and regulation of supply chains and employment relations during times of economic crisis. On the one hand, literature has highlighted pressures towards a degradation of standards as firms seek short-term cost advantages. This view is informed by various perspectives from organization studies to political economy but is united by the idea that structural changes in global capitalism drive how firms relate to their suppliers. On the other hand, it has been argued that counter-pressures range from consumer backlashes to the extension of formal and informal regulation across national boundaries. This undeniably heterogeneous literature has common themes suggesting that global forces may be mediated by existing embedded institutional arrangements at transnational, national and local level, and that there are still open-ended possibilities for social action. This chapter synthesizes and evaluates these two streams and identifies agendas for future research

The shock compression of microorganism-loaded broths and emulsions: Experiments and simulations

By carefully selecting flyer plate thickness and the geometry of a target capsule for bacterial broths and emulsions, we have successfully subjected the contents of the capsule to simultaneous shock and dynamic compression when subjected to a flyer-plate impact experiment. The capsules were designed to be recovered intact so that post experimental analysis could be done on the contents. ANSYS® AUTODYN hydrocode simulations were carried out to interrogate the deformation of the cover plate and the wave propagation in the fluid. Accordingly, we have shown that microorganisms such as Escherichia coli, Enterococcus faecalis and Zygosaccharomyces bailii are not affected by this type of loading regime. However, by introducing a cavity behind the broth we were able to observe limited kill in the yeast sample. Further, on using this latter technique with emulsions it was shown that greater emulsification of an oil-based emulsion occurred due to the cavitation that was introduced