Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Perceptions on healthy eating, physical activity and lifestyle advice: opportunities for adapting lifestyle interventions to individuals with low socioeconomic status
    Bukman, A.J. ; Teuscher, D. ; Feskens, E.J.M. ; Baak, M.A. van; Meershoek, A. ; Renes, R.J. - \ 2014
    BMC Public Health 14 (2014). - ISSN 1471-2458 - 22 p.
    deprived neighborhoods - diabetes prevention - european countries - leisure-time - women - inequalities - food - strategies - behaviors - weight
    Background Individuals with low socioeconomic status (SES) are generally less well reached through lifestyle interventions than individuals with higher SES. The aim of this study was to identify opportunities for adapting lifestyle interventions in such a way that they are more appealing for individuals with low SES. To this end, the study provides insight into perspectives of groups with different socioeconomic positions regarding their current eating and physical activity behaviour; triggers for lifestyle change; and ways to support lifestyle change. Methods Data were gathered in semi-structured focus group interviews among low SES (four groups) and high SES (five groups) adults. The group size varied between four and nine participants. The main themes discussed were perceptions and experiences of healthy eating, physical activity and lifestyle advice. Interviews were transcribed verbatim and a thematic approach was used to analyse the data. Results In general, three key topics were identified, namely: current lifestyle is logical for participants given their personal situation; lifestyle change is prompted by feedback from their body; and support for lifestyle change should include individually tailored advice and could profit from involving others. The perceptions of the low SES participants were generally comparable to the perceptions shared by the high SES participants. Some perceptions were, however, especially shared in the low SES groups. Low SES participants indicated that their current eating behaviour was sometimes affected by cost concerns. They seemed to be especially motivated to change their lifestyle when they experienced health complaints, but were rather hesitant to change their lifestyle for preventive purposes. Regarding support for lifestyle change, low SES participants preferred to receive advice in a group rather than on their own. For physical activities, groups should preferably consist of persons of the same age, gender or physical condition. Conclusions To motivate individuals with low SES to change their lifestyle, it may be useful to (visually) raise their awareness of their current weight or health status. Lifestyle interventions targeting individuals with low SES should take possible cost concerns into account and should harness the supportive effect of (peer) groups.
    Relative growth rate variation of evergreen and deciduous savanna tree species is driven by different traits
    Tomlinson, K.W. ; Poorter, L. ; Bongers, F. ; Borghetti, F. ; Jacobs, L. ; Langevelde, F. van - \ 2014
    Annals of Botany 114 (2014)2. - ISSN 0305-7364 - p. 315 - 324.
    phylogenetically independent contrasts - adaptive significance - carbohydrate storage - shade tolerance - seedling shade - woody-plants - allocation - biomass - forest - strategies
    Background and Aims Plant relative growth rate (RGR) depends on biomass allocation to leaves (leaf mass fraction, LMF), efficient construction of leaf surface area (specific leaf area, SLA) and biomass growth per unit leaf area (net assimilation rate, NAR). Functional groups of species may differ in any of these traits, potentially resulting in (1) differences in mean RGR of groups, and (2) differences in the traits driving RGR variation within each group. We tested these predictions by comparing deciduous and evergreen savanna trees. Methods RGR, changes to biomass allocation and leaf morphology, and root non-structural carbohydrate reserves were evaluated for juveniles of 51 savanna species (34 deciduous, 17 evergreen) grown in a common garden experiment. It was anticipated that drivers ofRGRwould differ between leaf habit groups because deciduous species have to allocate carbohydrates to storage in roots to be able to flush leaves again, which directly compromises their LMF, whereas evergreen species are not subject to this constraint. Key Results Evergreen species had greaterLMFandRGRthan deciduous species. Amongdeciduous speciesLMF explained 27% of RGR variation (SLA 34% and NAR 29 %), whereas among evergreen species LMF explained between 2 and 17% of RGR variation (SLA 32–35% and NAR 38–62 %). RGR and LMF were (negatively) related to carbohydrate storage only among deciduous species. Conclusions Trade-offs between investment in carbohydrate reserves and growth occurred only among deciduous species, leading to differences in relative contribution made by the underlying components of RGR between the leaf habit groups. The results suggest that differences in drivers ofRGRoccur among savanna species because these have different selected strategies for coping with fire disturbance in savannas. It is expected that variation in the drivers of RGR will be found in other functional types that respond differently to particular disturbances.
    A push-pull system to reduce house entry of malaria mosquitoes
    Menger, D.J. ; Otieno, B. ; Rijk, M. de; Mukabana, W.R. ; Loon, J.J.A. van; Takken, W. - \ 2014
    Malaria Journal 13 (2014). - ISSN 1475-2875 - 8 p.
    vector anopheles-gambiae - host-seeking behavior - mm-x traps - spatial repellency - field-evaluation - western kenya - lactic-acid - culicidae - diptera - strategies
    Background. Mosquitoes are the dominant vectors of pathogens that cause infectious diseases such as malaria, dengue, yellow fever and filariasis. Current vector control strategies often rely on the use of pyrethroids against which mosquitoes are increasingly developing resistance. Here, a push-pull system is presented, that operates by the simultaneous use of repellent and attractive volatile odorants. Method/Results. Experiments were carried out in a semi-field set-up: a traditional house which was constructed inside a screenhouse. The release of different repellent compounds, para-menthane-3,8-diol (PMD), catnip oil e.o. and delta-undecalactone, from the four corners of the house resulted in significant reductions of 45% to 81.5% in house entry of host-seeking malaria mosquitoes. The highest reductions in house entry (up to 95.5%), were achieved by simultaneously repelling mosquitoes from the house (push) and removing them from the experimental set-up using attractant-baited traps (pull). Conclusions. The outcome of this study suggests that a push-pull system based on attractive and repellent volatiles may successfully be employed to target mosquito vectors of human disease. Reductions in house entry of malaria vectors, of the magnitude that was achieved in these experiments, would likely affect malaria transmission. The repellents used are non-toxic and can be used safely in a human environment. Delta-undecalactone is a novel repellent that showed higher effectiveness than the established repellent PMD. These results encourage further development of the system for practical implementation in the field.
    Do males evaluate female age for precopulatory mate guarding in the two-spotted spider mite?
    Oku, K. ; Saito, Y. - \ 2014
    Journal of Ethology 32 (2014)1. - ISSN 0289-0771 - p. 1 - 6.
    linyphia-litigiosa linyphiidae - urticae koch acari - tetranychus-urticae - sex-pheromone - mating success - behavior - fertilization - strategies - ratio - time
    In the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae), because only the first mating results in fertilisation, adult males guard quiescent deutonymph females, the stage immediately before adult emergence. Previous studies showed that T. urticae males prefer to guard older rather than younger females. However, as previous experimental designs have included uncertain factors, findings have not always been sufficiently rigorous. Therefore, we reexamined whether T. urticae males discriminate between the females closest to becoming receptive and younger females. One male was introduced onto leaf squares with two differently aged quiescent deutonymph females, with time lags between the females of 3, 6, 12 or 23 h, and whether the older or younger female was guarded was recorded. When the time lags between the females were 3, 6 or 12 h, males showed no preferences. Males preferred older females over younger ones only when the time lag was 23 h. Under non-choice conditions, fewer males guarded the 23-h younger females than other older females, suggesting that the attractiveness of the younger females is weaker than older females. Our results are not fully consistent with previous studies; T. urticae males do not obviously discriminate between females closest to becoming receptive and younger females.
    A Unimodal Species Response Model Relating Traits to Environment with Application to Phytoplankton Communities.
    Jamil, T. ; Kruk, C. ; Braak, C.J.F. ter - \ 2014
    PLoS ONE 9 (2014)5. - ISSN 1932-6203 - 14 p.
    bayesian variable selection - climate-change - ecology - lake - variability - strategies - diversity - habitat - classification - regression
    In this paper we attempt to explain observed niche differences among species (i.e. differences in their distribution along environmental gradients) by differences in trait values (e.g. volume) in phytoplankton communities. For this, we propose the trait-modulated Gaussian logistic model in which the niche parameters (optimum, tolerance and maximum) are made linearly dependent on species traits. The model is fitted to data in the Bayesian framework using OpenBUGS (Bayesian inference Using Gibbs Sampling) to identify according to which environmental variables there is niche differentiation among species and traits. We illustrate the method with phytoplankton community data of 203 lakes located within four climate zones and associated measurements on 11 environmental variables and six morphological species traits of 60 species. Temperature and chlorophyll-a (with opposite signs) described well the niche structure of all species. Results showed that about 25% of the variance in the niche centres with respect to chlorophyll-a were accounted for by traits, whereas niche width and maximum could not be predicted by traits. Volume, mucilage, flagella and siliceous exoskeleton are found to be the most important traits to explain the niche centres. Species were clustered in two groups with different niches structures, group 1 high temperature-low chlorophyll-a species and group 2 low temperature-high chlorophyll-a species. Compared to group 2, species in group 1 had larger volume but lower surface area, had more often flagella but neither mucilage nor siliceous exoskeleton. These results might help in understanding the effect of environmental changes on phytoplankton community. The proposed method, therefore, can also apply to other aquatic or terrestrial communities for which individual traits and environmental conditioning factors are available.
    The Influence of Between-Farm Distance and Farm Size on the Spread of Classical Swine Fever during the 1997-1998 Epidemic in The Netherlands
    Boender, G.J. ; Hengel, R. van den; Roermund, H.J.W. van; Hagenaars, T.H.J. - \ 2014
    PLoS ONE 9 (2014)4. - ISSN 1932-6203 - 7 p.
    infectious-diseases - virus - transmission - strategies - model - risk
    As the size of livestock farms in The Netherlands is on the increase for economic reasons, an important question is how disease introduction risks and risks of onward transmission scale with farm size (i.e. with the number of animals on the farm). Here we use the epidemic data of the 1997–1998 epidemic of Classical Swine Fever (CSF) Virus in The Netherlands to address this question for CSF risks. This dataset is one of the most powerful ones statistically as in this epidemic a total of 428 pig farms where infected, with the majority of farm sizes ranging between 27 and 1750 pigs, including piglets. We have extended the earlier models for the transmission risk as a function of between-farm distance, by adding two factors. These factors describe the effect of farm size on the susceptibility of a ‘receiving’ farm and on the infectivity of a ‘sending’ farm (or ‘source’ farm), respectively. Using the best-fitting model, we show that the size of a farm has a significant influence on both farm-level susceptibility and infectivity for CSF. Although larger farms are both more susceptible to CSF and, when infected, more infectious to other farms than smaller farms, the increase is less than linear. The higher the farm size, the smaller the effect of increments of farm size on the susceptibility and infectivity of a farm. Because of changes in the Dutch pig farming characteristics, a straightforward extrapolation of the observed farm size dependencies from 1997/1998 to present times would not be justified. However, based on our results one may expect that also for the current pig farming characteristics in The Netherlands, farm susceptibility and infectivity depend non-linearly on farm size, with some saturation effect for relatively large farm sizes.
    The theoretical foundations of value-informed pricing in the service-dominant logic of marketing
    Ingenbleek, P.T.M. - \ 2014
    Management Decision 52 (2014)1. - ISSN 0025-1747 - p. 33 - 53.
    resource-advantage theory - managerial practice - decision-making - competition - perceptions - perspective - strategies - framework - companies - quality
    Purpose – In the mainstream normative pricing literature, value assessment is virtually non-existent. Although the resource-based literature recognizes that pricing is a competence, value-informed pricing practices are still weakly grounded in theory. The purpose of this paper is to strengthen the theoretical grounds of such pricing practices. Design/methodology/approach – The paper applies the emerging service-dominant logic of marketing to pricing. More specifically, it apples the ten foundational premises of service-dominant logic to pricing and it places pricing in the frameworks of one of the major building blocks of service-dominant logic, namely the resource-advantage theory of competition. Findings – From a service-dominant perspective, price is the reward for the application of specialized knowledge and skills. Pricing is an operant resource, or competence, that assesses customer value, applies it in multi-dimensional price propositions, and implements it in processes of co-creating prices with customers. Value-informed pricing is the central pricing practice within such competences. Practical implications – Prices vary among others between “good” and “bad”, firms generate competitive advantage not only through value creation, but also through pricing. Learning is key to develop pricing competences. Originality/value – This paper is the first to ground value-informed pricing at high levels of abstraction in general marketing theory.
    Forest Management Approaches for Coping with the Uncertainty of Climate Change: Trade-Offs in Service Provisioning and Adaptability.
    Wagner, S. ; Nocentini, S. ; Huth, F. ; Hoogstra, M.A. - \ 2014
    Ecology and Society 19 (2014)1. - ISSN 1708-3087
    fagus-sylvatica l. - ecosystem management - summer drought - central-europe - change impacts - strategies - future - sustainability - conservation - biodiversity
    The issue of rapid change in environmental conditions under which ecosystem processes and human interventions will take place in the future is relatively new to forestry, whereas the provision of ecosystem services, e.g., timber or fresh water, is at the very heart of the original concept of forest management. Forest managers have developed ambitious deterministic approaches to provide the services demanded, and thus the use of deterministic approaches for adapting to climate change seem to be a logical continuation. However, as uncertainty about the intensity of climate change is high, forest managers need to answer this uncertainty conceptually. One may envision an indeterministic approach to cope with this uncertainty; but how the services will be provided in such a concept remains unclear. This article aims to explore the fundamental aspects of both deterministic and indeterministic approaches used in forestry to cope with climate change, and thereby point out trade-offs in service provisioning and adaptability. A forest owner needs to be able to anticipate these trade-offs in order to make decisions towards sustainable forest management under climate change.
    Costs and effectiveness of on-farm measures to reduce aquatic risks from pesticides from the Netherlands
    Eerdt, M.M. van; Spruijt-Verkerke, J. ; Wal, A.J. van der; Zeijts, H. van; Tiktak, A. - \ 2014
    Pest Management Science 70 (2014)12. - ISSN 1526-498X - p. 1840 - 1849.
    integrated pest-management - agriculture - communities - strategies - ipm
    Background The European Union requires growers to implement the principles of Integrated Pest Management (IPM) by 2014. In this paper, we provide a quantitative overview of the costs and effectiveness of voluntary IPM measures in 15 crops in the Netherlands. We will focus on aquatic risks and define effectiveness as the potential to reduce the risks posed to aquatic organisms. We further identify which of these measures have actually been adopted by growers and why certain measures have not been adopted. Results Of the 105 measures evaluated, the most effective measures with respect to risk reduction were emission reduction and substitution of high-risk pesticides (each up to 80% reduction). IPM measures directed towards lowering pesticide use generally showed a smaller risk reducing potential. However, 40% of these measures reduced the overall cost of pest management. About 60% of all 105 measures were voluntarily implemented by growers. The most commonly adopted measures were pest prevention, low-dose spraying and spray drift reduction. Cost appeared to be an important incentive for adoption; however, other factors such as risk perception, education and practicability were equally important. Conclusions Voluntary IPM measures have significantly contributed to reducing aquatic risks (15-50% risk reduction depending on crop type). Further risk reduction could be achieved when more growers adopt the most effective measures like spray drift reduction and substitution of high-risk pesticides. However, IPM hardly reduced the number of pesticide applications and therefore the dependence on chemical crop protection continued to be high.
    The impact of uncertainties on predicted GHG emissions of dairy cow production systems
    Zehetmeier, M. ; Gandorfer, M. ; Hoffmann, H. ; Muller, U.K. ; Boer, I.J.M. de - \ 2014
    Journal of Cleaner Production 73 (2014). - ISSN 0959-6526 - p. 116 - 124.
    nitrous-oxide emissions - life-cycle assessment - environmental-impact - carbon footprint - milk-production - agriculture - methane - sensitivity - strategies - germany
    Dairy farms produce significant greenhouse gas (GHG) emissions and are therefore a focal point for GHG-mitigation practices. To develop viable mitigation options, we need robust (insensitive to changes in model parameters and assumptions) predictions of GHG emissions. To this end, we developed a stochastic model to estimate the robustness of predictions based on input parameters (GHG emission factors and production traits) and their uncertainties. In our study we explored how sensitive predictions of GHG emissions are to three factors: (1) system boundaries of the emission model (2) the uncertainty of input parameters due to quality of data or methodological choices (epistemic uncertainty) and (3) inherent variability in input parameters (variability uncertainty). To assess the effect of system boundaries, we compared two different boundaries: the “dairy farm gate” boundary (all GHG emissions are allocated to milk) and “system expansion” (the model gives a GHG credit to beef derived from culled cows and bull, heifer and calf fattening of surplus dairy calves outside the farm). Results using the farm-gate boundary provide guidance to dairy farmers to reduce GHG emissions of milk production. The results using system expansion are important for defining GHG abatement policies for milk and beef production. We found that the choice of system boundary had the strongest impact on the level and variation of predicted GHG emissions. Model predictions were least robust for lower-yielding dairy cow production systems and when we used system expansion. We also explored which GHG-abatement strategies have the most leverage by assessing the influence of each input parameter on model predictions. Predicted GHG emissions were least sensitive to variability-related uncertainty in production traits (i.e. replacement rate, calving interval). Lower-yielding production systems had the highest variation, indicating the highest potential for GHG mitigation of all production systems studied. Variation in predicted GHG emissions increased substantially when both epistemic and variability uncertainty in emission factors and variability uncertainty in production traits were included in the model. If the system boundary was set at the farm gate, the emission factor of N2O from nitrogen input into the soil had the highest impact on variation in predicted GHG emissions. This variation stems from uncertainties in predicting N2O emissions (epistemic uncertainty) but also from inherent variability of N2O emissions over time and space. The uncertainty of predicted GHG emissions can be reduced by increasing the precision in predicting N2O emissions. However, this additional information does not reduce GHG emissions itself. Knowing site specific variability of N2O emissions can help reduce GHG emissions by specific management (e.g. reduce soil compaction, adopted manure management, choice of suitable crops). In case of system expansion, uncertainty in GHG emission credit for dairy beef contributed the most to increasing the variation in predicted GHG emissions. The stochastic-model approach gave important insights into the robustness of model outcomes, which is crucial in the search for cost-effective GHG-abatement options. Despite the high degree of uncertainty when using system expansion, its results help identifying global GHG mitigation options of combined milk and beef production
    Analysis of trade-offs in agricultural systems: current status and way forward
    Klapwijk, C.J. ; Wijk, M.T. van; Rosenstock, T.S. ; Asten, P.J.A. van; Thornton, P.K. ; Giller, K.E. - \ 2014
    Current Opinion in Environmental Sustainability 6 (2014)2. - ISSN 1877-3435 - p. 110 - 115.
    crop-livestock systems - land-use - conservation agriculture - management-practices - climate-change - africa - strategies - knowledge - resource - science
    Trade-off analysis has become an increasingly important approach for evaluating system level outcomes of agricultural production and for prioritizing and targeting management interventions in multifunctional agricultural landscapes. We review the state-of-the-art for trade-off analysis, assessing different techniques by exploring a concrete example of trade-offs around the use of crop residues in smallholder farming systems. The techniques for performing trade-off analyses have developed substantially in recent years aided by mathematical advancement, increased computing power, and emerging insights into systems behaviour. Combining different techniques allows the assessment of aspects of system behaviour via various perspectives, thereby generating complementary knowledge. However, this does not solve the fundamental challenge: trade-off analyses without substantial stakeholder engagement often have limited practical utility for informing practical decision-making. We suggest ways to integrate approaches and improve the potential for societal impact of future trade-off analyses.
    Gaming for smallholder participation in the design of more sustainable agricultural landscapes
    Speelman, E.N. ; García-Barrios, L.E. ; Groot, J.C.J. ; Tittonell, P.A. - \ 2014
    Agricultural Systems 126 (2014). - ISSN 0308-521X - p. 62 - 75.
    role-playing game - educational simulation tool - laboratory experiments - collective action - biosphere reserve - field experiments - decision-making - social dilemmas - lab experiments - strategies
    Smallholder farming systems often consist of a mosaic of interlinked forested and cleared-field patches that together provide a diversity of services to local and non-local stakeholders. Designing and adopting more sustainable farming systems for such mosaic landscapes involves communal decision-making and active participation of local smallholders. Currently, a wide variety of participatory approaches to involve individual farmers in such design processes is available. However, methodologies that address communal decision-making processes as seen in complex smallholder agricultural landscapes are still rare. Here, we present a gaming methodology developed to (i) actively involve farmers in the process of agroecosystem design, and (ii) to identify factors and patterns of communal decision-making through an in-depth analysis of game strategies deployed by participants. At the basis of this methodology is the RESORTES board game; a stylized yet complex land-use game rich in ecological and social outcomes. Results of four pilot sessions in a usufruct community in the buffer zone of a Man and Biosphere Reserve in Chiapas, Mexico, showed that the game sessions created an open and active discussion among participants. Discussions concerned land-use issues in the game and in real-life. It allowed participants that were new to active involvement in communal decision-making to openly discuss and share their ideas. The highly structured monitoring and analysis scheme for ex-ante/ex-post analysis was easy in use and identified communication, leadership and relatedness among participants as influential factors that smoothened the collective decision-making process. The RESORTES board game and related games can shed light on farmer’s actual views on and responses to multifunctional agricultural landscape planning and the land sharing vs. land sparing dilemmas currently in debate in academic and policy-making settings. The findings of this paper can be useful to inform strategies for community involvement in agroecosystem design in a broader set of complex socio-environmental context, using serious game to guide agricultural landscape planning processes.
    Refreshing the role of open water surfaces on mitigating the maximum urban heat island effect
    Steeneveld, G.J. ; Koopmans, S. ; Heusinkveld, B.G. ; Theeuwes, N.E. - \ 2014
    Landscape and Urban Planning 121 (2014). - ISSN 0169-2046 - p. 92 - 96.
    land-use - temperature - comfort - strategies - index - uk
    During warm summer episodes citizens in urban areas are subject to reduced human thermal comfort and negative health effects. To mitigate these adverse effects, land use planners and urban designers have used the evaporative power of water bodies as a tool to limit the urban heat island effect (UHI) and undesirable human thermal comfort. Based on weather observations by Dutch hobby meteorologists and a station network in Rotterdam (Netherlands), we show that water bodies increase rather than decrease the 95 percentile of the daily maximum UHI. The high heat capacity of water suppresses the diurnal and annual cycle over water, and water temperatures remain relatively high after evening and season transitions. This is reflected to the 2 m temperature above and in the surround of the water body, and in a relatively high UHI. Our result has consequences for the daily practice in urban design concerning microclimate effects.
    Climate-proofing spatial planning and water management projects: an analysis of 100 local and regional projects in the Netherlands
    Sedee, A.G.J. ; Swart, R.J. ; Pater, F. de; Goosen, H. ; Pijnappels, M.H.J. ; Vellinga, P. - \ 2014
    Journal of Environmental Policy and Planning 16 (2014)1. - ISSN 1523-908X - p. 55 - 74.
    klimaatverandering - regionale planning - waterbeheer - onderzoeksprojecten - inventarisaties - nederland - climatic change - regional planning - water management - research projects - inventories - netherlands - adaptation - strategies
    Since the turn of the century, an increasing number of local and regional authorities in Europe started making their city or region resilient to climate change, or ‘climate-proof’. Publications about the actual experiences with implementing these adaptation policies are as yet anecdotal, determined by the local context and the methods applied. In order to identify common processes and characteristics, moving beyond individual cases, this paper systematically assesses 100 spatial planning and water management projects in the Netherlands that included climate resilience as one of their objectives. We derive eight defining characteristics that not only increase climate resilience, but are also found to lead to a greater ‘quality’ of the project area. We structure these properties into a stylized sequence: (i) a longer timeframe, (ii) an integrative and sustainable approach, (iii) consideration of new spatial functions, (iv) a broader spatial context, (v) participation of multiple stakeholders, (vi) new opportunities for entrepreneurs, (vii) increased cost-effectiveness, and (viii) enhanced quality of the project area. The assessment also suggests four process-related conditions that contribute to the success of a project: early incorporation of adaptation; multi-actor collaboration and co-creation of knowledge; integrated, multifunctional and forward-looking solutions; and early political commitment.
    Pareto optimality and robustness in bi-blending problems
    Herrera, J.F. ; Casado, L.G. ; Hendrix, E.M.T. ; García, I. - \ 2014
    TOP 22 (2014)1. - ISSN 1134-5764 - p. 254 - 273.
    strategies
    The mixture design problem for two products concerns finding simultaneously two recipes of a blending problem with linear, quadratic and semi-continuity constraints. A solution of the blending problem minimizes a linear cost objective and an integer valued objective that keeps track of the number of raw materials that are used by the two recipes, i.e. this is a bi-objective problem. Additionally, the solution must be robust. We focus on possible solution approaches that provide a guarantee to solve bi-blending problems with a certain accuracy, where two products are using (partly) the same scarce raw materials. The bi-blending problem is described, and a search strategy based on Branch-and-Bound is analysed. Specific tests are developed for the bi-blending aspect of the problem. The whole is illustrated numerically.
    The Fatter the Tail, the Fatter the Climate Agreement. Simulating the Influence of Fat Tails in Climate Change Damages on the Success of International Climate Negotiations
    Dellink, R.B. ; Dekker, T. ; Ketterer, J. - \ 2013
    Environmental and Resource Economics 56 (2013)2. - ISSN 0924-6460 - p. 277 - 305.
    international environmental agreements - stability likelihood - uncertainty - coalitions - strategies
    International climate negotiations take place in a setting where uncertainties regarding the impacts of climate change are very large. In this paper, we examine the influence of increasing the probability and impact of large climate change damages, also known as the ‘fat tail’, on the formation of an international mitigation agreement. We systematically vary the shape and location of the distribution of climate change damages using the stochastic version of the applied game-theoretical STACO model. Our aim is to identify how changes to the distributional form affect the stability of coalitions and their performance. We find that fatter upper tails increase the likelihood that more ambitious coalitions are stable as well as the performance of these stable coalitions. Fatter tails thus imply more successful, or ‘fatter’, international climate agreements
    Cold storage affects mortality, body mass, lifespan, reproduction and flight capacity of Praon volucre (Hymenoptera: Braconidae)
    Lins, J.C. ; Bueno, V.H.P. ; Sidney, L.A. ; Silva, D.B. ; Sampaio, M.V. ; Pereira, J.M. ; Nomelini, Q.S.S. ; Lenteren, J.C. van - \ 2013
    European Journal of Entomology 110 (2013)2. - ISSN 1210-5759 - p. 263 - 270.
    parasitoid species hymenoptera - aphidius-colemani hymenoptera - biological-control - low-temperatures - fat reserves - survival - quality - ervi - perspective - strategies
    The possibility of storing natural enemies at low temperatures is important for the mass production of biological control agents. We evaluated the effect of different periods of cold storage on immature mortality, mummy body mass, lifespan, reproduction and flight capacity of the parasitoid Praon volucre (Haliday). One-day-old mummies of the aphid Macrosiphum euphorbiae (Thomas) containing pre-pupae of P. volucre were stored in a climatic chamber at 5 degrees C and 70 +/- 10% RH in the dark for different periods of time (5, 10, 15 and 20 days). The control consisted of mummies kept at 22 +/- 1 degrees C, 70 +/- 10% RH and a 12 h photophase. Percentage adult emergence, mummy body mass, flight capacity and number of eggs in the ovarioles of P. volucre females decreased with increase in the period of storage, while the longevity of females was only slightly affected. Fat content of mummies, percentage of parasitized aphids and survival of progeny to emergence decreased with increase in the period of storage. Storage of P. volucre pre-pupae for up to 5 days at 5 degrees C did not affect any of the above mentioned parameters. The fact that P. volucre pre-pupae can be stored for 5 days without loss of quality and for 10 days with only a slight loss facilitates the planning of mass production and shipment.
    A bodyguard or a tastier meal? Dying caterpillar indirectly protects parasitoid cocoons by offering alternate prey to a generalist predator
    Harvey, J.A. ; Weber, D. ; Clercq, P. De; Gols, R. - \ 2013
    Entomologia Experimentalis et Applicata 149 (2013). - ISSN 0013-8703 - p. 219 - 228.
    cotesia-glomerata l. - host behavior - insect parasitoids - manipulation - wasp - hyperparasitism - populations - braconidae - strategies - usurpation
    In some parasitic Hymenoptera the dying caterpillars remain attached or close to the parasitoid cocoons. It has been suggested that the caterpillars act as ‘bodyguards’ for the vulnerable cocoons and therefore protect them against predators and/or hyperparasitoids (the ‘usurpation hypothesis’). This hypothesis has been demonstrated in associations where the caterpillars remain active and/or aggressive after parasitism. However, in other associations the caterpillars are so physiologically depleted after parasitism that they are unable to physically defend the cocoons and instead sit atop them in a moribund state. In this study a generalist predator, the spined soldier bug, Podisus maculiventris Say (Hemiptera: Pentatomidae), was provided with cocoons of the gregarious endoparasitoid Cotesia glomerata L. and the solitary endoparasitoid Microplitis mediator Haliday (both Hymenoptera: Braconidae), in turn attended by their hosts, Pieris brassicae L. (Lepidoptera: Pieridae) and Mamestra brassicae L. (Lepidoptera: Noctuidae), respectively. Cotesia glomerata produces broods of up to 40 cocoons and the dying caterpillars sit atop the cocoons where they exhibit little response to physical stimuli. Previous studies reported that dying P. brassicae caterpillars were ineffective bodyguards against two species of hyperparasitoids. In both associations, the dying host caterpillars were significantly preferred as food by P. maculiventris over the parasitoid cocoons. However, in absence of caterpillars, the bugs readily attacked the C. glomerata cocoons. Alternatively, the survival of M. mediator was very low, irrespective of whether a caterpillar was present or not. Caterpillars attacked by M. mediator are several times smaller than those attacked by C. glomerata. Consequently, the predators ran out of food much more quickly in the former and switched from one prey to the other. We show that in some host–parasitoid associations the dying caterpillars provide more visually apparent or nutritionally superior prey, rather than acting as bodyguards.
    Ecosystem-based coastal defence in the face of global change
    Temmerman, S. ; Meire, P. ; Bouma, T.J. ; Herman, P.M.J. ; Ysebaert, T. ; Vriend, H.J. de - \ 2013
    Nature 504 (2013). - ISSN 0028-0836 - p. 79 - 83.
    tidal marsh - scheldt estuary - climate-change - storm surges - sea-level - restoration - sedimentation - strategies - mangroves - carbon
    The risk of flood disasters is increasing for many coastal societies owing to global and regional changes in climate conditions, sea-level rise, land subsidence and sediment supply. At the same time, in many locations, conventional coastal engineering solutions such as sea walls are increasingly challenged by these changes and their maintenance may become unsustainable. We argue that flood protection by ecosystem creation and restoration can provide a more sustainable, cost-effective and ecologically sound alternative to conventional coastal engineering and that, in suitable locations, it should be implemented globally and on a large scale.
    Maximizing the nitrogen efficiency of a prototype mixed crop-livestock farm in The Netherlands
    Lantinga, E.A. ; Boele, E. ; Rabbinge, R. - \ 2013
    NJAS Wageningen Journal of Life Sciences 66 (2013). - ISSN 1573-5214 - p. 15 - 22.
    ammonia volatilization - slurry manure - dairy farm - management - soil - system - strategies - emissions - protein - marke
    This paper describes the year-over-year improvement of the nitrogen (N) efficiency in a prototype mixed farm system through the implementation of a coherent set of ecotechnological adjustments. This farm, the former APMinderhoudhoeve, was located on a marine clay loam soil in Oostelijk Flevoland, the Netherlands, reclaimed from the sea in the late 1950s. The designed farm structure was representative for the Dutch soil-bound agriculture in the late 1990s in terms of food crops’ choice and average level of milk production per ha of farmland. Key management strategies were the inclusion of grass-clover leys in the 7-year crop rotation, restricted grazing of the dairy herd and protein-poor and fibre-rich cattle diets including cereal straw. The farm components animal-manure-soil-crop were analysed in-depth in order to evaluate N flows and soil organic matter (SOM) dynamics at the farm system level, covering a period of six years. In its final experimental state, farm N use efficiency, expressed as the proportion of purchased crop fertilizers and cattle feed that was sold as exported products (crops, milk and cattle), was as high as 73%, Besides, total environmental losses were as low as 42 kg N ha-1 yr-1. A scenario analysis revealed that these losses could be further minimized to 30 kg N ha-1 yr-1 in the stabilization phase, of which one-third as leached nitrate and a somewhat higher fraction as volatilized ammonia. The remaining losses represented mainly denitrified harmless N2 from the stored animal slurry and farmyard manure. Soil N accumulated at an average rate of 89 kg N ha-1 yr-1, whereas SOM showed a positive trend but with fluctuations from year to year which were negatively related to the annual rainfall amount. Despite the lowered protein content in the cow diets, average annual milk production increased from 8100 tot 8700 kg cow-1. This could be mainly ascribed to a lower cow replacement rate due to less animal health problems, leading to an increased average lactation number of the dairy herd. Overall, the obtained environmental side effects on the prototype farm in its final experimental state were already below the targets set by the European Union with respect to the Nitrate Directive for the year 2020. It is concluded that when the best ecotechnological means are combined in a balanced mixed farm system a multiple win situation is attained in terms of food production capacity, cattle health and environmental quality.
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