Searching for (un)sustainabilty in pangasius aquaculture: A political economy of quality in European retail

Drawing on a political economy of food quality, this paper investigates the main sources of uncertainty over the environmental sustainability of Vietnamese pangasius catfish in European markets and how retailers subsequently respond to these uncertainties. Based on media survey and interviews with supermarket retailers across Europe between 2008 and 2010, the analysis focuses on the claims and counterclaims over the sustainability of pangasius aquaculture, how retailers have dealt with the uncertainty these claims have engendered about the fish, and what effect this uncertainty has had on the potential of marketing ‘sustainable pangasius’ in European supermarkets. The paper concludes that successful claims around new food qualities like sustainability by retailers are dependent on the ability of regulatory networks to overcome any perceived illegitimacy of imported products in the face of continuing uncertainty and the wider politics of market protectionism.     

Understanding river dune splitting through flume experiments and analysis of a dune evolution model

Forecasts of water level during river floods require accurate predictions of the evolution of river dune dimensions, because the hydraulic roughness of the main channel is largely determined by the bed morphology. River dune dimensions are controlled by processes like merging and splitting of dunes. Particularly the process of dune splitting is still poorly understood and – as a result – not yet included in operational dune evolution models. In the current paper, the process of dune splitting is investigated by carrying out laboratory experiments and by means of a sensitivity analysis using a numerical dune evolution model. In the numerical model, we introduced superimposed TRIAS ripples (i.e. triangular asymmetric stoss side‐ripples) on the stoss sides of underlying dunes as soon as these stoss sides exceed a certain critical length. Simulations with the model including dune splitting showed that predictions of equilibrium dune characteristics were significantly improved compared to the model without dune splitting. As dune splitting is implemented in a parameterized way, the computational cost remains low which means that dune evolution can be calculated on the timescale of a flood wave. Subsequently, we used this model to study the mechanism of dune splitting. Literature showed that the initiation of a strong flow separation zone behind a superimposed bedform is one of the main mechanisms behind dune splitting. The flume experiments indicated that besides its height also the lee side slope of the superimposed bedform is an important factor to determine the strength of the flow separation zone and therefore is an important aspect in dune splitting. The sensitivity analysis of the dune evolution model showed that a minimum stoss side length was required to develop a strong flow separation zone. Copyright © 2014 John Wiley & Sons, Ltd.     

Race/Ethnicity in Visual Imagery of Dutch Nature Conservation Organizations

Nature conservation organizations in various Western countries, including the Netherlands, have noted that racial/ethnic minorities compared to Whites are “underparticipating” in recreation in natural areas and in nature conservation practices. Previous research trying to explain (under-)participation by racial/ethnic minorities in outdoor recreation and nature conservation mainly focused on characteristics of racial/ethnic groups. This study argues that nature conservation organizations themselves—although in all likelihood unintentionally—may play a role in participation of racial/ethnic minorities as well, through their promotional material. A content analysis of 22,974 pictures in magazines and on websites of four large Dutch nature conservation organizations shows that only 3.8% of the depicted people were non-White. Our results indicate that visual imagery of nature conservation organizations, at least in the Netherlands, (re)produces an image of outdoor recreation and nature conservation as being activities almost exclusively performed by Whites.     

Uncertainty in Integrated Assessment Modelling

Integrated Assessment (IA) aims to facilitate decision-making processes on complex issues. Dealing with uncertainty is principally at the core of Integrated Assessment. IA practitioners realise that. However: – Not all uncertainties can be adequately addressed with existingmethods and tools. This especially holds for uncertainty in model structure and uncertainty due to behavioural and societal variability, value diversity, technological surprise, ignorance and indeterminacy. – Uncertainty is usually treated as a marginal issue, as an additional physical variable, as a mathematical artifact. The current methods merely involve evaluation of the impacts of `certain uncertainties', i.e. uncertainties for which estimates or probability distributions are available.– Current methods give no indication of the magnitude and sources of thevarious underlying uncertainties and the aggregated uncertainty measures are difficult to understand to decision-makers and other audiences.Within the International Centre for Integrative Studies, Maastricht University (the Netherlands), the research project `Perspectives on uncertainty and risk' aims to develop alternative, complementary approaches to uncertainty management in Integrated Assessment. The current paper summarises the theoretical analysis of the concept of uncertainty, and it proposes a typology of sources of uncertainty. This paper further discusses insights and experiences with pluralistic uncertainty management in thecontext of Integrated Assessment modelling in order to assess the strengths and weaknesses of such an approach. Although systematic fundamental uncertainty research is still needed in the context of Integrated Assessment, this paper argues that significant profit in quality terms can be gained by using the available methods, including the pluralistic approach, more consciously and systematically.     

应用能量平衡方法对黄河上中游水文气象要素监测及校验

利用能量平衡方法建立能量与水平衡系统(EWBMS)对黄河上中游地区进行实时监测,并将其监测要素实际蒸散发、温度、净辐射、显热通量等与观测值比较,从而进一步说明EW'BMS的准确性和可靠性.     

Cichlid species diversity in naturally and anthropogenically turbid habitats of Lake Victoria, East Africa

During the past decades, major anthropogenic environmental changes occurred in Lake Victoria, including increased predation pressure due to Nile perch introduction, and decreases in water transparency and dissolved oxygen concentrations due to eutrophication. This resulted in a collapse of the haplochromine cichlids in the sub-littoral waters of the Mwanza Gulf in 1986–1990, followed by a recovery of some species in the 1990s and 2000s, when Nile perch densities declined. We studied two data sets: (1) haplochromines from sand and mud bottoms in the pre-collapse period; (2) haplochromines from sub-littoral areas during the pre-collapse, collapse and recovery periods. Water over mud is murkier and poorer in oxygen than water over sand, and differences in haplochromine communities in these natural habitats during the pre-collapse period may predict the effects of anthropogenic eutrophication during the collapse and recovery periods. In the pre-collapse period, haplochromine densities over sand and mud did not differ, but species richness over sand was 1.6 times higher than over mud bottoms. Orange- and white-blotched colour morphs were most common at the shallowest sand station. More specifically, insectivores and mollusc-shellers had higher numbers of species over sand than over mud, whereas for mollusc-crushers no difference was found. Laboratory experiments revealed that mollusc shelling was more affected by decreased light intensities than mollusc crushing. During the pre-collapse period, spawning occurred year-round in shallow areas with hard substrates and relatively clear water. In deeper areas with mud bottoms, spawning mainly occurred during months in which water clarity was high. No effects of hypoxia on spawning periods were found. It follows that clearer water seems to support differentiation in feeding techniques as well as year-round spawning, and both may facilitate species coexistence. Water clarity is also known to be important for mate choice. These observations may explain why, since the decline of Nile perch, haplochromine densities have recovered, the numbers of hybrids increased and species diversity in the current eutrophic sub-littoral waters has remained 70 % lower than before the environmental changes.     

Solidarity in transboundary flood risk management: A view from the Dutch North Rhine–Westphalian catchment area

Climate change is putting pressure on water systems, and its effects transcend man-made boundaries, making cooperation across territorial borders essential. The governance of transboundary flood risk management calls for solidarity among riparians, as climate change will make river basins more prone to flooding. ‘Solidarity’ means that individuals act to support members of a particular community to which they belong. Recently, the solidarity principle has become institutionalized due to its formalization in the EU Floods Directive. However, it is not clear what solidarity means in the upstream–downstream practices of transboundary flood risk management. Understanding the meaning of solidarity is important for the development of cross-border climate adaptation governance. This article discusses the conceptualization of the solidarity principle and explores its meaning for international cooperation in the Dutch North Rhine–Westphalian border region. Our critical case study reveals that although all actors understand the importance of solidarity, they interpret it differently, often based on self-interest related to their position in the catchment. The formal inclusion of the solidarity principle in the Floods Directive can best be seen as a step in the continuous development of transboundary flood risk governance, as no striking changes in practice have been identified after its formalization.

Policy relevance

As climate change increasingly puts pressure on river basins and other shared resources, cross-border cooperation and solidarity are seen as increasingly important. This article discusses the meaning of solidarity in practice and reveals how this normative principle may contribute to transboundary climate adaptation governance. Understanding its meaning is important for future cross-border climate adaptation governance.     

Modelling the effect of time‐dependent river dune evolution on bed roughness and stage

This paper presents an approach to incorporate time‐dependent dune evolution in the determination of bed roughness coefficients applied in hydraulic models. Dune roughness is calculated by using the process‐based dune evolution model of Paarlberg et al. ( 2009 ) and the empirical dune roughness predictor of Van Rijn ( 1984 ). The approach is illustrated by applying it to a river of simple geometry in the 1‐D hydraulic model SOBEK for two different flood wave shapes. Calculated dune heights clearly show a dependency on rate of change in discharge with time: dunes grow to larger heights for a flood wave with a smaller rate of change. Bed roughness coefficients computed using the new approach can be up to 10% higher than roughness coefficients based on calibration, with the largest differences at low flows. As a result of this larger bed roughness, computed water depths can be up to 15% larger at low flow. The new approach helps to reduce uncertainties in bed roughness coefficients of flow models, especially for river systems with strong variations in discharge with time. Copyright © 2010 John Wiley & Sons, Ltd.