Marten Scheffer

Wageningen University, Wageningen, Gelderland, Netherlands

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Publications (236)1097.7 Total impact

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    ABSTRACT: Aquaculture is the fastest growing food sector and continues to expand alongside terrestrial crop and livestock production. Using portfolio theory as a conceptual framework, we explore how current interconnections between the aquaculture, crop, livestock, and fisheries sectors act as an impediment to, or an opportunity for, enhanced resilience in the global food system given increased resource scarcity and climate change. Aquaculture can potentially enhance resilience through improved resource use efficiencies and increased diversification of farmed species, locales of production, and feeding strategies. However, aquaculture's reliance on terrestrial crops and wild fish for feeds, its de-pendence on freshwater and land for culture sites, and its broad array of environmental impacts diminishes its ability to add resilience. Feeds for livestock and farmed fish that are fed rely largely on the same crops, although the fraction destined for aquaculture is presently small (∼4%). As demand for high-value fed aquaculture products grows, competition for these crops will also rise, as will the demand for wild fish as feed inputs. Many of these crops and forage fish are also consumed directly by humans and provide essential nutrition for low-income households. Their rising use in aquafeeds has the potential to increase price levels and volatility, worsening food insecurity among the most vulnerable populations. Although the diversification of global food production systems that includes aquaculture offers promise for enhanced resilience, such promise will not be realized if government policies fail to provide adequate incentives for resource efficiency, equity, and environmental protection. food portfolio management | crop resources | diversity | shocks | global change
    Proceedings of the National Academy of Sciences. 08/2014; 23.
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    ABSTRACT: An analysis of the maximum height of woody plant species across the globe reveals that an intermediate size is remarkably rare. We speculate that this may be due to intrinsic suboptimality or to ecosystem bistability with open landscapes favouring shrubs, and closed canopies propelling trees to excessive tallness.
    Trends in Ecology & Evolution 08/2014; 29(8):433-434. · 15.39 Impact Factor
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    ABSTRACT: Background: Mathematical modeling approaches are becoming ever more established in clinical neuroscience. They provide insight that is key to understand complex interactions of network phenomena, in general, and interactions within the migraine generator network, in particular. Purpose: In this study, two recent modeling studies on migraine are set in the context of premonitory symptoms that are easy to confuse for trigger factors. This causality confusion is explained, if migraine attacks are initiated by a transition caused by a tipping point. Conclusion: We need to characterize the involved neuronal and autonomic subnetworks and their connections during all parts of the migraine cycle if we are ever to understand migraine. We predict that mathematical models have the potential to dismantle large and correlated fluctuations in such subnetworks as a dynamical network biomarker of migraine.
    Cephalalgia : an international journal of headache. 04/2014;
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    ABSTRACT: Recent studies show that the microbial communities inhabiting the human intestine can have profound impact on our well-being and health. However, we have limited understanding of the mechanisms that control this complex ecosystem. Based on a deep phylogenetic analysis of the intestinal microbiota in a thousand western adults we identified groups of bacteria that tend to be either nearly absent, or abundant in most individuals. The abundances of these bimodally distributed bacteria vary independently, and their contrasting alternative states are associated with host factors such as ageing and overweight. We propose that such bimodal groups represent independent tipping elements of the intestinal microbiota. These reflect the overall state of the intestinal ecosystem whose critical transitions can have profound health implications and diagnostic potential.
    Nature Communications 04/2014; 5. · 10.02 Impact Factor
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    Proceedings of the National Academy of Sciences 03/2014; 111(10):E879. · 9.81 Impact Factor
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    ABSTRACT: Declines in pollinator populations may harm biodiversity and agricultural productivity. Little attention has, however, been paid to the systemic response of mutualistic communities to global environmental change. Using a modelling approach and merging network theory with theory on critical transitions, we show that the scale and nature of critical transitions is likely to be influenced by the architecture of mutualistic networks. Specifically, we show that pollinator populations may collapse suddenly once drivers of pollinator decline reach a critical point. A high connectance and/or nestedness of the mutualistic network increases the capacity of pollinator populations to persist under harsh conditions. However, once a tipping point is reached, pollinator populations collapse simultaneously. Recovering from this single community-wide collapse requires a relatively large improvement of conditions. These findings may have large implications for our view on the sustainability of pollinator communities and the services they provide.
    Ecology Letters 01/2014; · 17.95 Impact Factor
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    ABSTRACT: The invasion of Nile perch into LakeVictoria is one of the iconic examples of the destructive effect of an ntroduced species on an ecosystem but no convincing explanation exists of why Nile perch only increased dramatically after a 25 year lag. Here, we consider this problem using a mathematical model that takes into account interactions between Nile perch and its cichlid prey. We examined competing hypotheses to explain Nile perch invasion and show that suppression of juvenile Nile perch by cichlids may cause the system to have two alternative stable states: one with only cichlids and onewith coexistence of cichlids and Nile perch. Without cichlid predation on Nile perch, alternative stable states did not occur. Our analysis indicates that cichlid mortality, for example fishing mortality, may have induced the observed shift between the states.
    Theoretical Ecology 01/2014; · 2.05 Impact Factor
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    ABSTRACT: A number of ecosystems can exhibit abrupt shifts between alternative stable states. Because of their important ecological and economic consequences, recent research has focused on devising early warning signals for anticipating such abrupt ecological transitions. In particular, theoretical studies show that changes in spatial characteristics of the system could provide early warnings of approaching transitions. However, the empirical validation of these indicators lag behind their theoretical developments. Here, we summarize a range of currently available spatial early warning signals, suggest potential null models to interpret their trends, and apply them to three simulated spatial data sets of systems undergoing an abrupt transition. In addition to providing a step-by-step methodology for applying these signals to spatial data sets, we propose a statistical toolbox that may be used to help detect approaching transitions in a wide range of spatial data. We hope that our methodology together with the computer codes will stimulate the application and testing of spatial early warning signals on real spatial data.
    PLoS ONE 01/2014; 9(3):e92097. · 3.53 Impact Factor
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    ABSTRACT: About 17% of humanity goes through an episode of major depression at some point in their lifetime. Despite the enormous societal costs of this incapacitating disorder, it is largely unknown how the likelihood of falling into a depressive episode can be assessed. Here, we show for a large group of healthy individuals and patients that the probability of an upcoming shift between a depressed and a normal state is related to elevated temporal autocorrelation, variance, and correlation between emotions in fluctuations of autorecorded emotions. These are indicators of the general phenomenon of critical slowing down, which is expected to occur when a system approaches a tipping point. Our results support the hypothesis that mood may have alternative stable states separated by tipping points, and suggest an approach for assessing the likelihood of transitions into and out of depression.
    Proceedings of the National Academy of Sciences 12/2013; · 9.81 Impact Factor
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    ABSTRACT: It has recently been found that the frequency distribution of remotely sensed tree cover in the tropics has three distinct modes, which seem to correspond to forest, savanna and treeless states. This pattern has been suggested to imply that these states represent alternative attractors, and that the response of these systems to climate change would be characterized by critical transitions and hysteresis. Here, we show how this inference is contingent upon mechanisms at play. We present a simple dynamical model that can generate three alternative tree cover states (forest, savanna and a treeless state), based on known mechanisms, and use this model to simulate patterns of tree cover under different scenarios. We use these synthetic data to show that the hysteresis inferred from remotely sensed tree cover patterns will be inflated by spatial heterogeneity of environmental conditions. On the other hand, we show that the hysteresis inferred from satellite data may actually underestimate real hysteresis in response to climate change if there exists a positive feedback between regional tree cover and precipitation. Our results also indicate that such positive feedback between vegetation and climate should cause direct shifts between forest and a treeless state (rather than through an intermediate savanna-state) to become more likely. Lastly, we show how directionality of historical change in conditions may bias the observed relationship between tree cover and environmental conditions. This article is protected by copyright. All rights reserved.
    Global Change Biology 09/2013; · 8.22 Impact Factor
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    ABSTRACT: Climatic warming is substantially intensifying the global water cycle and is projected to increase rainfall variability. Using satellite data, we show that higher climatic variability is associated with reduced tree cover in the wet tropics globally. In contrast, interannual variability in rainfall can have neutral or even positive effects on tree cover in the dry tropics. In South America, tree cover in dry lands is higher in areas with high year-to-year variability in rainfall. This is consistent with evidence from case studies suggesting that in these areas rare wet episodes are essential for opening windows of opportunity where massive tree recruitment can overwhelm disturbance effects, allowing the establishment of extensive woodlands. In Australia, wet extremes have similar effects, but the net effect of rainfall variability is overwhelmed by negative effects of extreme dry years. In Africa, effects of rainfall variability are neutral for dry lands. It is most likely that differences in herbivore communities and fire regimes contribute to regulating tree expansion during wet extremes. Our results illustrate that increasing climatic variability may affect ecosystem services in contrasting, and sometimes surprising, ways. Expansion of dry tropical tree cover during extreme wet events may decrease grassland productivity but enhance carbon sequestration, soil nutrient retention and biodiversity.
    Nature Climate Change. 08/2013; 3(8):755-758.
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    ABSTRACT: * Dominance of free-floating plants such as duckweed is undesirable as it indicates eutrophication. The objectives of this study are to investigate whether the onset of duckweed dominance is related to weather conditions by analysing field observations, to evaluate the effect of different climate scenarios on the timing of duckweed dominance using a model and to evaluate to what extent nutrient levels should be lowered to counteract effects of global warming. * To analyse the onset of duckweed dominance in relation to weather conditions, duckweed cover in Dutch ditches was correlated with weather conditions for the period 1980–2005. Furthermore, a model was developed that describes biomass development over time as a function of temperature, light and nutrient availability, crowding and mortality. This model was used to evaluate the effects of climate change scenarios and the effects of lowering nutrients. * The onset of duckweed dominance in the field advanced by approximately 14 days with an increase of 1 °C in the average maximum daily winter temperature. The modelled biomass development correlated well with the field observations. Scenarios showed that expected climate change will affect onset and duration of duckweed dominance in temperate ditches. Reducing nutrient levels may counteract the effect of warming. * Synthesis and applications. Global warming may lead to an increase in the dominance of free-floating plants in drainage ditches in the Netherlands. The expected reductions in nutrient-loading to surface waters as a result of different measures taken so far are likely not sufficient to counteract these effects of warming. Therefore, additional measures should be taken to avoid a further deterioration of the ecological water quality in ditches.
    Journal of Applied Ecology 07/2013; 50:585-593. · 4.74 Impact Factor
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    ABSTRACT: Abstract The theory of limiting similarity predicts that co-occurring species must be sufficiently different to coexist. Although this idea is a staple of community ecology, convincing empirical evidence has been scarce. Here we examine 34 subterranean beetle communities in arid inland Australia that share the same habitat type but have evolved in complete isolation over the past 5 million years. Although these communities come from a range of phylogenetic origins, we find that they have almost invariably evolved to share a similar size structure. The relative positions of coexisting species on the body size axis were significantly more regular across communities than would be expected by chance, with a size ratio, on average, of 1.6 between coexisting species. By contrast, species' absolute body sizes varied substantially from one community to the next. This suggests that self-organized spacing according to limiting-similarity theory, as opposed to evolution toward preexisting fixed niches, shaped the communities. Using a model starting from random sets of founder species, we demonstrate that the patterns are indeed consistent with evolutionary self-organization. For less isolated habitats, the same model predicts the coexistence of multiple species in each regularly spaced functional group. Limiting similarity, therefore, may also be compatible with the coexistence of many redundant species.
    The American Naturalist 07/2013; 182(1):67-75. · 4.55 Impact Factor
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    ABSTRACT: REPLYING TO J. Carstensen, R. J. Telford & H. J. B. Birks 498, http://dx.doi.org/nature12272 (2013)Some issues have been raised with regard to our paper, by Carstensen et al.. In terms of our data processing, we were aware from the outset of the problems of unevenly spaced temporal data and sediment dating errors. We also wanted to duplicate, as far as possible, the methods published previously that had been used to identify early warning signals in palaeoenvironmental data (for example, ref. 3). Thus, we applied two standard smoothing functions (exponential and Gaussian kernel) to interpolated and non-interpolated (original) diatom data, expressed as three statistical indices (detrended correspondence analysis (DCA), Hill's diversity index N2 (HDI) and correspondence analysis), using different sliding-window sizes and the two-standard-deviation range of dates for each sample.
    Nature 06/2013; 498(7455):E12-E13. · 38.60 Impact Factor
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    ABSTRACT: Life on Earth has repeatedly displayed abrupt and massive changes in the past, and there is no reason to expect that comparable planetary-scale regime shifts will not continue in the future. Different lines of evidence indicate that regime shifts occur when the climate or biosphere transgresses a tipping point. Whether human activities will trigger such a global event in the near future is uncertain, due to critical knowledge gaps. In particular, we lack understanding of how regime shifts propagate across scales, and whether local or regional tipping points can lead to global transitions. The ongoing disruption of ecosystems and climate, combined with unprecedented breakdown of isolation by human migration and trade, highlights the need to operate within safe planetary boundaries.
    Trends in Ecology & Evolution 06/2013; · 15.39 Impact Factor
  • Ecological Applications 04/2013; 23(3):671-5. · 3.82 Impact Factor
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    ABSTRACT: 1. A collapse of Nile perch stocks of Lake Victoria could affect up to 30 million people. Furthermore, changes in Nile perch population size-structure and stocks make the threat of collapse imminent. However, whether eutrophication or fishing will be the bane of Nile perch is still debated. 2. Here, we attempt to unravel how changes in food resources, a side effect of eutrophication, and fishing mortality determine fish population growth and size structures. We parameterised a physiologically structured model to Nile perch, analysed the influence of ontogenetic diet shifts and relative resource abundances on existence boundaries of Nile perch and described the populations on either side of these boundaries. 3. Our results showed that ignoring ontogenetic diet shifts can lead to over-estimating the maximum sustainable mortality of a fish population. Size distributions can be indicators of processes driving population dynamics. However, the vulnerability of stocks to fishing mortality is dependent on its environment and is not always reflected in size distributions. 4. We suggest that the ecosystem, instead of populations, should be used to monitor long-term effects of human impact.
    Freshwater Biology 04/2013; 58(4):828-840. · 3.93 Impact Factor
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    ABSTRACT: Self-propagating waves of cerebral neuronal firing, known as spreading depolarisations, are believed to be at the roots of migraine attacks. We propose that the start of spreading depolarisations corresponds to a critical transition that occurs when dynamic brain networks approach a tipping point. We show that this hypothesis is consistent with current pathogenetic insights and observed dynamics. Our view implies that migraine strikes when modulating factors further raise the neuronal excitability in genetically predisposed subjects to a level where even minor perturbations can trigger spreading depolarisations. A corollary is that recently discovered generic early warning indicators for critical transitions may be used to predict the onset of migraine attacks even before patients are clinically aware. This opens up new avenues for dissecting the mechanisms for the onset of migraine attacks and for identifying novel prophylactic treatment targets for the prevention of attacks.
    PLoS ONE 01/2013; 8(8):e72514. · 3.53 Impact Factor
  • Remi Vergnon, Egbert H. van Nes, Marten Scheffer
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    ABSTRACT: Formulated in 2006, Scheffer and van Nes’ Emergent neutrality model predicts that competing species might self‐organize into groups of species similar in their traits. Recently, Vergnon et al. showed that the model consistently generates multimodal species abundance distributions, in accordance with empirical data. Barabás et al. argue that Emergent neutrality model relies on unmodeled, ‘hidden’ species differences. They also suggest that an Emergent neutrality model explicitly integrating such differences may fail to generate multimodal species abundance distributions, while other models can robustly produce those patterns. Here we demonstrate that density dependence – the process deemed problematic by Barabás et al. – may permanently maintain groups of similar species without need for additional species differences. More broadly, we make it clear that density dependence is not the only likely mechanism that could allow the permanent coexistence of similar species in the Emergent neutrality framework. We welcome the finding that models other than Emergent neutrality can generate multimodal abundance distributions and we briefly discuss their novelty and relevance.
    Oikos 01/2013; 122(11). · 3.33 Impact Factor
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    ABSTRACT: Nile perch (Lates niloticus) suddenly invaded Lake Victoria between 1979 and 1987, 25 years after its introduction in the Ugandan side of the lake. Nile perch then replaced the native fish diversity and irreversibly altered the ecosystem and its role to lakeshore societies: it is now a prised export product that supports millions of livelihoods. The delay in the Nile perch boom led to a hunt for triggers of the sudden boom and generated several hypotheses regarding its growth at low abundances - all hypotheses having important implications for the management of Nile perch stocks. We use logistic growth as a parsimonious null model to predict when the Nile perch invasion should have been expected, given its growth rate, initial stock size and introduction year. We find the first exponential growth phase can explain the timing of the perch boom at the scale of Lake Victoria, suggesting that complex mechanisms are not necessary to explain the Nile perch invasion or its timing. However, the boom started in Kenya before Uganda, indicating perhaps that Allee effects act at smaller scales than that of the whole Lake. The Nile perch invasion of other lakes indicates that habitat differences may also have an effect on invasion success. Our results suggest there is probably no single management strategy applicable to the whole lake that would lead to both efficient and sustainable exploitation of its resources.
    PLoS ONE 01/2013; 8(10):e76847. · 3.53 Impact Factor

Publication Stats

10k Citations
1,097.70 Total Impact Points

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Institutions

  • 1997–2014
    • Wageningen University
      • Department of Aquatic Ecology and Water Quality Management
      Wageningen, Gelderland, Netherlands
  • 2013
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2012–2013
    • University of Southampton
      Southampton, England, United Kingdom
    • University of Exeter
      • College of Life and Environmental Sciences
      Exeter, ENG, United Kingdom
  • 2011
    • Greenland Institute of Natural Resources
      Nuuk, Sermersooq, Greenland
    • University of Maine
      • School of Marine Sciences
      Orono, MN, United States
    • University of Wisconsin - Milwaukee
      • Department of Biological Sciences
      Milwaukee, WI, United States
  • 1995–2011
    • University of Amsterdam
      • Institute for Biodiversity and Ecosystem Dynamics
      Amsterdam, North Holland, Netherlands
  • 2010
    • Leibniz-Institute of Freshwater Ecology and Inland Fisheries
      Berlín, Berlin, Germany
  • 2009
    • Aarhus University
      • Department of Bioscience
      Aarhus, Central Jutland, Denmark
  • 2007
    • Netherlands Institute of Ecology (NIOO-KNAW)
      Wageningen, Gelderland, Netherlands
  • 2006
    • University of Manitoba
      • Natural Resources Institute
      Winnipeg, Manitoba, Canada