Kelvin–Helmholtz instability in the presence of variable viscosity for mudflow resuspension in estuaries

The temporal stability of a parallel shear flow of miscible fluid layers of different density and viscosity is investigated through a linear stability analysis and direct numerical simulations. The geometry and rheology of this Newtonian fluid mixing can be viewed as a simplified model of the behavior of mudflow at the bottom of estuaries for suspension studies. In this study, focus is on the stability and transition to turbulence of an initially laminar configuration. A parametric analysis is performed by varying the values of three control parameters, namely the viscosity ratio, the Richardson and Reynolds numbers, in the case of initially identical thickness of the velocity, density and viscosity profiles. The range of parameters has been chosen so as to mimic a wide variety of real configurations. This study shows that the Kelvin–Helmholtz instability is controlled by the local Reynolds and Richardson numbers of the inflection point. In addition, at moderate Reynolds number, viscosity stratification has a strong influence on the onset of instability, the latter being enhanced at high viscosity ratio, while at high Reynolds number, the influence is less pronounced. In all cases, we show that the thickness of the mixing layer (and thus resuspension) is increased by high viscosity stratification, in particular during the non-linear development of the instability and especially pairing processes. This study suggests that mud viscosity has to be taken into account for resuspension parameterizations because of its impact on the inflection point Reynolds number and the viscosity ratio, which are key parameters for shear instabilities.     

Seasonal modulation of flight speed among nocturnal passerine migrants: differences between short- and long-distance migrants

Migrating birds are expected to fly at higher airspeeds when minimizing time rather than energy costs of their migratory journeys. Spring migration has often been suggested to be more time selected than autumn migration, because of the advantage of early arrival at breeding sites. We have earlier demonstrated that nocturnal passerine migrants fly at higher airspeeds during spring compared to autumn, supporting time-selected spring migration. In this study, we test the hypothesis that seasonal airspeeds are modulated differently between short- and long-distance migrants, because of a stronger element of time selection for autumn migration over long distances. In support of this hypothesis, we demonstrate that the seasonal difference in airspeed is significantly larger (spring airspeed exceeding autumn airspeed by a factor of 1.16 after correcting for the influence of altitude, wind and climb/descent on airspeed) among short-distance compared to long-distance (factor 1.12) migrants. This result is based on a large sample of tracking radar data from 3 years at Falsterbo, South Sweden. Short-distance migrants also tend to fly with more favourable winds during autumn, indicating relaxed time constraints (being able to afford to wait for favourable winds) compared to long-distance migrants. These results indicate surprisingly fine-tuned seasonal modulation of airspeed and responses to wind, associated with behavioural strategies adapted to different levels of time selection pressures during spring and autumn migration.     

How democratic innovations realise democratic goods. Two case studies of area committees in the Netherlands

Participatory planning is becoming increasingly integral to governance. Numerous planning innovations are developed which aim to increase democratic legitimacy and improve decision making. This paper critically reflects on a typical Dutch innovation: the area committee. Based on two individual case studies, we investigate whether area committees realise democratic legitimacy in existing planning practices. Analytically, we focus on four democratic goods: inclusiveness, popular control, considered judgement and transparency. Based on the interdependencies between area committees and government structures we discuss the potential and dilemmas for the area committee to contribute to the democratic legitimacy of environmental policy and rural development.     

The water vulnerability of metro and megacities: An investigation of structural determinants

Urban areas are becoming increasingly subject to and vulnerable to water‐related natural disasters. Urban areas are a kind of socio‐ecological system wherein the human development dynamics co‐evolve with the natural dynamics. Most of the literature is focused on the impact of natural disasters on human development; we evaluate the impacts of human development on natural disasters and present an analysis of this phenomenon in the context of megacities. The approach is exploratory and begins with the construction of a database on the 595 existing megacities in the world. Multifactor analysis is then used to determine the main characteristics of these megacities. Finally, three structural components (maturity, anthropization and centrality) are identified and then correlated with data on water‐related hazards, distinguishing groups of cities according to their structure and factors of vulnerability to water‐related risks.     

First trimester diagnosis of lesch-nyhan syndrome: Applications to other disorders of purine metabolism

The prenatal detection of hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8) deficiency, the Lesch-Nyhan syndrome, during the first trimester of an affected pregnancy through the use of chorionic villus sampling is reported. Quantitation of reaction products formed by villus cell extracts from exogenous hypoxanthine-8-[¹⁴C] or adenine-8-[¹⁴C] is used in diagnosis. We report the diagnosis of Lesch-Nyhan syndrome using a chorionic villus specimen and confirmation of that diagnosis. In addition, adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP), enzymes deficient in inherited immune disorders, are detected in chorionic villus samples. These heritable disorders also appear amenable to early prenatal diagnosis.     

Major challenges of integrating agriculture into climate change mitigation policy frameworks

Taking the European Union (EU) as a case study, we simulate the application of non-uniform national mitigation targets to achieve a sectoral reduction in agricultural non-carbon dioxide (CO₂) greenhouse gas (GHG) emissions. Scenario results show substantial impacts on EU agricultural production, in particular, the livestock sector. Significant increases in imports and decreases in exports result in rather moderate domestic consumption impacts but induce production increases in non-EU countries that are associated with considerable emission leakage effects. The results underline four major challenges for the general integration of agriculture into national and global climate change mitigation policy frameworks and strategies, as they strengthen requests for (1) a targeted but flexible implementation of mitigation obligations at national and global level and (2) the need for a wider consideration of technological mitigation options. The results also indicate that a globally effective reduction in agricultural emissions requires (3) multilateral commitments for agriculture to limit emission leakage and may have to (4) consider options that tackle the reduction in GHG emissions from the consumption side.     

Forest Biodiversity Monitoring for REDD+: A Case Study of Actors’ Views in Peru

The climate change mitigation mechanism Reducing Emissions from Deforestation and Forest Degradation in developing countries (REDD+) is currently being negotiated under the United Nations Framework Convention on Climate Change (UNFCCC). Integrating biodiversity monitoring into REDD+ facilitates compliance with the safeguards stipulated by the UNFCCC to exclude environmental risks. Interviews with actors engaged in REDD+ implementation and biodiversity conservation at the national and sub-national level in Peru (n = 30) and a literature review (n = 58) were conducted to pinpoint constraints and opportunities for monitoring effects of REDD+ management interventions on biodiversity, and to identify relevant biodiversity data and indicators. It was found that particularly sub-national actors, who were frequently involved in REDD+ pilot projects, acknowledge the availability of biodiversity data. Actors at both the national and sub-national levels, however, criticized data gaps and data being scattered across biodiversity research organizations. Most of the literature reviewed (78 %) included indicators on the state of certain biodiversity aspects, especially mammals. Indicators for pressure on biodiversity, impacts on environmental functions, or policy responses to environmental threats were addressed less frequently (31, 21, and 10 %, respectively). Integrating biodiversity concerns in carbon monitoring schemes was considered to have potential, although few specific examples were identified. The involvement of biodiversity research organizations in sub-national REDD+ activities enhances monitoring capacities. It is discussed how improvements in collaboration among actors from the project to the national level could facilitate the evaluation of existing information at the national level. Monitoring changes in ecosystem services may increase the ecological and socioeconomic viability of REDD+.     

Pro-Environmental Beach Driving is Uncommon and Ineffective in Reducing Disturbance to Beach-Dwelling Birds

Vehicles on beaches cause numerous deleterious effects to coastal wildlife. These impacts may, hypothetically, be lessened if drivers act to reduce disturbance. Since it is unknown to what extent such behavior occurs, and whether it can reduce disturbance, we quantified the behavior of drivers who encountered birds on open-coast, sandy beaches in eastern Australia and the consequent bird responses. Drivers of commercial tourist buses never slowed or altered course (“evaded birds”) to avoid disturbing birds; conversely, 34 % of drivers of private cars did evade birds. Drivers of vehicles with fishing rod holders tended (P = 0.09) to evade birds more frequently than non-fishing vehicles. Evasion, when it occurred, was modest, and did not significantly decrease the intensity of bird response or the probability of escapes on the wing. Voluntary behavioral adjustments to alleviate impacts on wildlife may be unworkable, suggesting that other solutions (e.g., beach closures) might be the only effective and feasible way to reduce disturbance to birds on ocean beaches.     

Human impact on wild firewood species in the Rural Andes community of Apillapampa, Bolivia

Firewood is the basic fuel source in rural Bolivia. A study was conducted in an Andean village of subsistence farmers to investigate human impact on wild firewood species. A total of 114 different fuel species was inventoried during fieldtrips and transect sampling. Specific data on abundance and growth height of wild firewood species were collected in thirty-six transects of 50 ×2 m². Information on fuel uses of plants was obtained from 13 local Quechua key participants. To appraise the impact of fuel harvest, the extraction impact value (EIV) index was developed. This index takes into account local participants?? appreciation of (1) decreasing plant abundance; (2) regeneration capacity of plants; (3) impact of root harvesting; and (4) quality of firewood. Results suggest that several (sub-)woody plant species are negatively affected by firewood harvesting. We found that anthropogenic pressure, expressed as EIV, covaried with density of firewood species, which could entail higher human pressure on more abundant and/or more accessible species. The apparent negative impact of anthropogenic pressure on populations of wild fuel species is corroborated by our finding that, in addition to altitude, several anthropogenic variables (i.e. site accessibility, cultivation of exotics and burning practices) explain part of the variation in height of firewood species in the surroundings of Apillapampa.