TY - JOUR A1 - Augusiak, Jacqueline A1 - Van den Brink, Paul J. A1 - Grimm, Volker T1 - Merging validation and evaluation of ecological models to 'evaludation': A review of terminology and a practical approach JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Confusion about model validation is one of the main challenges in using ecological models for decision support, such as the regulation of pesticides. Decision makers need to know whether a model is a sufficiently good representation of its real counterpart and what criteria can be used to answer this question. Unclear terminology is one of the main obstacles to a good understanding of what model validation is, how it works, and what it can deliver. Therefore, we performed a literature review and derived a standard set of terms. 'Validation' was identified as a catch-all term, which is thus useless for any practical purpose. We introduce the term 'evaludation', a fusion of 'evaluation' and 'validation', to describe the entire process of assessing a model's quality and reliability. Considering the iterative nature of model development, the modelling cycle, we identified six essential elements of evaludation: (i) 'data evaluation' for scrutinising the quality of numerical and qualitative data used for model development and testing; (ii) 'conceptual model evaluation' for examining the simplifying assumptions underlying a model's design; (iii) 'implementation verification' for testing the model's implementation in equations and as a computer programme; (iv) 'model output verification' for comparing model output to data and patterns that guided model design and were possibly used for calibration; (v) 'model analysis' for exploring the model's sensitivity to changes in parameters and process formulations to make sure that the mechanistic basis of main behaviours of the model has been well understood; and (vi) 'model output corroboration' for comparing model output to new data and patterns that were not used for model development and parameterisation. Currently, most decision makers require 'validating' a model by testing its predictions with new experiments or data. Despite being desirable, this is neither sufficient nor necessary for a model to be useful for decision support. We believe that the proposed set of terms and its relation to the modelling cycle can help to make quality assessments and reality checks of ecological models more comprehensive and transparent. (C) 2013 Elsevier B.V. All rights reserved. KW - Model validation KW - Terminology KW - Decision support KW - Documentation KW - Ecological models KW - Risk assessment Y1 - 2014 U6 - https://doi.org/10.1016/j.ecolmodel.2013.11.009 SN - 0304-3800 SN - 1872-7026 VL - 280 SP - 117 EP - 128 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ayllon, Daniel A1 - Grimm, Volker A1 - Attinger, Sabine A1 - Hauhs, Michael A1 - Simmer, Clemens A1 - Vereecken, Harry A1 - Lischeid, Gunnar T1 - Cross-disciplinary links in environmental systems science BT - Current state and claimed needs identified in a meta-review of process models JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Terrestrial environmental systems are characterised by numerous feedback links between their different compartments. However, scientific research is organized into disciplines that focus on processes within the respective compartments rather than on interdisciplinary links. Major feedback mechanisms between compartments might therefore have been systematically overlooked so far. Without identifying these gaps, initiatives on future comprehensive environmental monitoring schemes and experimental platforms might fail. We performed a comprehensive overview of feedbacks between compartments currently represented in environmental sciences and explores to what degree missing links have already been acknowledged in the literature. We focused on process models as they can be regarded as repositories of scientific knowledge that compile findings of numerous single studies. In total, 118 simulation models from 23 model types were analysed. Missing processes linking different environmental compartments were identified based on a meta-review of 346 published reviews, model inter-comparison studies, and model descriptions. Eight disciplines of environmental sciences were considered and 396 linking processes were identified and ascribed to the physical, chemical or biological domain. There were significant differences between model types and scientific disciplines regarding implemented interdisciplinary links. The most wide-spread interdisciplinary links were between physical processes in meteorology, hydrology and soil science that drive or set the boundary conditions for other processes (e.g., ecological processes). In contrast, most chemical and biological processes were restricted to links within the same compartment. Integration of multiple environmental compartments and interdisciplinary knowledge was scarce in most model types. There was a strong bias of suggested future research foci and model extensions towards reinforcing existing interdisciplinary knowledge rather than to open up new interdisciplinary pathways. No clear pattern across disciplines exists with respect to suggested future research efforts. There is no evidence that environmental research would clearly converge towards more integrated approaches or towards an overarching environmental systems theory. (c) 2017 Elsevier B.V. All rights reserved. KW - Review KW - Interdisciplinary links KW - Integrated environmental modelling KW - Research needs Y1 - 2018 U6 - https://doi.org/10.1016/j.scitotenv.2017.12.007 SN - 0048-9697 SN - 1879-1026 VL - 622 SP - 954 EP - 973 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ayllon, Daniel A1 - Railsback, Steven Floyd A1 - Vincenzi, Simone A1 - Groeneveld, Juergen A1 - Almodoevar, Ana A1 - Grimm, Volker T1 - InSTREAM-Gen: Modelling eco-evolutionary dynamics of trout populations under anthropogenic environmental change JF - Ecological modelling : international journal on ecological modelling and engineering and systems ecolog N2 - Current rates of environmental change are exceeding the capacity of many populations to adapt to new conditions and thus avoid demographic collapse and ultimate extinction. In particular, cold-water freshwater fish species are predicted to experience strong selective pressure from climate change and a wide range of interacting anthropogenic stressors in the near future. To implement effective management and conservation measures, it is crucial to quantify the maximum rate of change that cold-water freshwater fish populations can withstand. Here, we present a spatially explicit eco-genetic individual-based model, inSTREAM-Gen, to predict the eco-evolutionary dynamics of stream-dwelling trout under anthropogenic environmental change. The model builds on a well-tested demographic model, which includes submodels of river dynamics, bioenergetics, and adaptive habitat selection, with a new genetic module that allows exploration of genetic and life-history adaptations to new environments. The genetic module models the transmission of two key traits, size at emergence and maturity size threshold. We parameterized the model for a brown trout (Salmo trutta L.) population at the warmest edge of its range to validate it and analyze its sensitivity to parameters under contrasting thermal profiles. To illustrate potential applications of the model, we analyzed the population's demographic and evolutionary dynamics under scenarios of (1) climate change-induced warming, and (2) warming plus flow reduction resulting from climate and land use change, compared to (3) a baseline of no environmental change. The model predicted severe declines in density and biomass under climate warming. These declines were lower than expected at range margins because of evolution towards smaller size at both emergence and maturation compared to the natural evolution under the baseline conditions. Despite stronger evolutionary responses, declining rates were substantially larger under the combined warming and flow reduction scenario, leading to a high probability of population extinction over contemporary time frames. Therefore, adaptive responses could not prevent extinction under high rates of environmental change. Our model demonstrates critical elements of next generation ecological modelling aiming at predictions in a changing world as it accounts for spatial and temporal resource heterogeneity, while merging individual behaviour and bioenergetics with microevolutionary adaptations. KW - Individual-based model KW - Eco-genetic modelling KW - Eco-evolution KW - Climate change KW - Brown trout KW - Next-generation modelling Y1 - 2016 U6 - https://doi.org/10.1016/j.ecolmodel.2015.07.026 SN - 0304-3800 SN - 1872-7026 VL - 326 SP - 36 EP - 53 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bailleul, Frederic A1 - Grimm, Volker A1 - Chion, Clement A1 - Hammill, Mike T1 - Modeling implications of food resource aggregation on animal migration phenology JF - Ecology and evolution N2 - The distribution of poikilotherms is determined by the thermal structure of the marine environment that they are exposed to. Recent research has indicated that changes in migration phenology of beluga whales in the Arctic are triggered by changes in the thermal structure of the marine environment in their summering area. If sea temperatures reflect the spatial distribution of food resources, then changes in the thermal regime will affect how homogeneous or clumped food is distributed. We explore, by individual-based modelling, the hypothesis that changes in migration phenology are not necessarily or exclusively triggered by changes in food abundance, but also by changes in the spatial aggregation of food. We found that the level of food aggregation can significantly affect the relationship between the timing of the start of migration to the winter grounds and the total prey capture of individuals. Our approach strongly indicates that changes in the spatial distribution of food resources should be considered for understanding and quantitatively predicting changes in the phenology of animal migration. KW - Animal migration KW - food structuring KW - global change KW - individual-based model KW - polar environment Y1 - 2013 U6 - https://doi.org/10.1002/ece3.656 SN - 2045-7758 VL - 3 IS - 8 SP - 2535 EP - 2546 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Becher, Matthias A. A1 - Grimm, Volker A1 - Thorbek, Pernille A1 - Horn, Juliane A1 - Kennedy, Peter J. A1 - Osborne, Juliet L. T1 - BEEHAVE: a systems model of honeybee colony dynamics and foraging to explore multifactorial causes of colony failure JF - Journal of applied ecology : an official journal of the British Ecological Society N2 - BEEHAVE offers a valuable tool for researchers to design and focus field experiments, for regulators to explore the relative importance of stressors to devise management and policy advice and for beekeepers to understand and predict varroa dynamics and effects of management interventions. We expect that scientists and stakeholders will find a variety of applications for BEEHAVE, stimulating further model development and the possible inclusion of other stressors of potential importance to honeybee colony dynamics. KW - Apis mellifera KW - colony decline KW - cross-level interactions KW - feedbacks KW - foraging KW - modelling KW - multiple stressors KW - multi-agent simulation KW - predictive systems ecology KW - Varroa destructor Y1 - 2014 U6 - https://doi.org/10.1111/1365-2664.12222 SN - 0021-8901 SN - 1365-2664 VL - 51 IS - 2 SP - 470 EP - 482 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Becher, Matthias A. A1 - Osborne, Juliet L. A1 - Thorbek, Pernille A1 - Kennedy, Peter J. A1 - Grimm, Volker T1 - Towards a systems approach for understanding honeybee decline - a stocktaking and synthesis of existing models JF - Journal of applied ecology : an official journal of the British Ecological Society N2 - 1. The health of managed and wild honeybee colonies appears to have declined substantially in Europe and the United States over the last decade. Sustainability of honeybee colonies is important not only for honey production, but also for pollination of crops and wild plants alongside other insect pollinators. A combination of causal factors, including parasites, pathogens, land use changes and pesticide usage, are cited as responsible for the increased colony mortality. 2. However, despite detailed knowledge of the behaviour of honeybees and their colonies, there are no suitable tools to explore the resilience mechanisms of this complex system under stress. Empirically testing all combinations of stressors in a systematic fashion is not feasible. We therefore suggest a cross-level systems approach, based on mechanistic modelling, to investigate the impacts of (and interactions between) colony and land management. 3. We review existing honeybee models that are relevant to examining the effects of different stressors on colony growth and survival. Most of these models describe honeybee colony dynamics, foraging behaviour or honeybee - varroa mite - virus interactions. 4. We found that many, but not all, processes within honeybee colonies, epidemiology and foraging are well understood and described in the models, but there is no model that couples in-hive dynamics and pathology with foraging dynamics in realistic landscapes. 5. Synthesis and applications. We describe how a new integrated model could be built to simulate multifactorial impacts on the honeybee colony system, using building blocks from the reviewed models. The development of such a tool would not only highlight empirical research priorities but also provide an important forecasting tool for policy makers and beekeepers, and we list examples of relevant applications to bee disease and landscape management decisions. KW - Apis mellifera KW - colony decline KW - feedbacks KW - integrated model KW - multiple stressors KW - predictive systems ecology KW - review Y1 - 2013 U6 - https://doi.org/10.1111/1365-2664.12112 SN - 0021-8901 VL - 50 IS - 4 SP - 868 EP - 880 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Berger, Uta A1 - Piou, Cyril A1 - Schiffers, Katja A1 - Grimm, Volker T1 - Competition among plants : concepts, individual-based modelling approaches, and a proposal for a future research strategy N2 - Competition is a key process in plant populations and communities. We thus need, if we are to predict the responses of ecological systems to environmental change, a comprehensive and mechanistic understanding of plant competition. Considering competition, however, only at the population level is not sufficient because plant individuals usually are different, interact locally, and can adapt their behaviour to the current state of themselves and of their biotic and abiotic environment. Therefore, simulation models that are individual-based and spatially explicit are increasingly used for studying competition in plant systems. Many different individual-based modelling approaches exist to represent competition, but it is not clear how good they are in reflecting essential aspects of plant competition. We therefore first summarize current concepts and theories addressing plant competition. Then, we review individual-based approaches for modelling competition among plants. We distinguish between approaches that are used for more than 10 years and more recent ones. We identify three major gaps that need to be addressed more in the future: the effects of plants on their local environment, adaptive behaviour, and below-ground competition. To fill these gaps, the representation of plants and their interactions have to be more mechanistic than most existing approaches. Developing such new approaches is a challenge because they are likely to be more complex and to require more detailed knowledge and data on individual-level processes underlying competition. We thus need a more integrated research strategy for the future, where empirical and theoretical ecologists as well as computer scientists work together on formulating, implementing, parameterization, testing, comparing, and selecting the new approaches. (c) 2008 Rubel Foundation, ETH Zurich. Published by Elsevier GmbH. All rights reserved. Y1 - 2008 SN - 1433-8319 ER - TY - JOUR A1 - Cortes-Avizanda, Ainara A1 - Jovani, Roger A1 - Antonio Donazar, Jose A1 - Grimm, Volker T1 - Bird sky networks: How do avian scavengers use social information to find carrion? JF - Ecology : a publication of the Ecological Society of America N2 - The relative contribution of personal and social information to explain individual and collective behavior in different species and contexts is an open question in animal ecology. In particular, there is a major lack of studies combining theoretical and empirical approaches to test the relative relevance of different hypothesized individual behaviors to predict empirical collective patterns. We used an individual-based model to confront three hypotheses about the information transfer between social scavengers (Griffon Vultures, Gyps fulvus) when searching for carrion: (1) Vultures only use personal information during foraging ("nonsocial" hypothesis); (2) they create long chains of vultures by following both other vultures that are flying towards carcasses and vultures that are following other vultures that are flying towards carcasses ("chains of vultures" hypothesis); and (3) vultures are only attracted by other vultures that are sinking vertically to a carcass ("local enhancement" hypothesis). The chains of vultures hypothesis has been used in existing models, but never been confronted with field data. Testing is important, though, because these hypotheses could have different management implications. The model was parameterized to mimic the behavior and the densities of both Griffon Vultures and carcasses in a 10 000-km(2) study area in northeastern Spain. We compared the number of vultures attending simulated carcasses with those attending 25 continuously monitored experimental carcasses in the field. Social hypotheses outperformed the nonsocial hypothesis. The chains of vultures hypothesis overestimated the number of vultures feeding on carcasses; the local enhancement hypothesis fitted closely to the empirical data. Supported by our results, we discuss mechanistic and adaptive considerations that reveal that local enhancement may be the key social mechanism behind collective foraging in this and likely other avian scavengers and/or social birds. It also highlights the current need for more studies confronting alternative models of key behaviors with empirical patterns in order to understand how collective behavior emerges in animal societies. KW - carrion resources KW - foraging KW - group-living KW - pulsed resources KW - sociality KW - Spain KW - vultures Y1 - 2014 SN - 0012-9658 SN - 1939-9170 VL - 95 IS - 7 SP - 1799 EP - 1808 PB - Wiley CY - Washington ER - TY - JOUR A1 - Crawford, Michael A1 - Jeltsch, Florian A1 - May, Felix A1 - Grimm, Volker A1 - Schlägel, Ulrike E. T1 - Intraspecific trait variation increases species diversity in a trait-based grassland model JF - Oikos N2 - Intraspecific trait variation (ITV) is thought to play a significant role in community assembly, but the magnitude and direction of its influence are not well understood. Although it may be critical to better explain population persistence, species interactions, and therefore biodiversity patterns, manipulating ITV in experiments is challenging. We therefore incorporated ITV into a trait‐ and individual‐based model of grassland community assembly by adding variation to the plants’ functional traits, which then drive life‐history tradeoffs. Varying the amount of ITV in the simulation, we examine its influence on pairwise‐coexistence and then on the species diversity in communities of different initial sizes. We find that ITV increases the ability of the weakest species to invade most, but that this effect does not scale to the community level, where the primary effect of ITV is to increase the persistence and abundance of the competitively‐average species. Diversity of the initial community is also of critical importance in determining ITV's efficacy; above a threshold of interspecific diversity, ITV does not increase diversity further. For communities below this threshold, ITV mainly helps to increase diversity in those communities that would otherwise be low‐diversity. These findings suggest that ITV actively maintains diversity by helping the species on the margins of persistence, but mostly in habitats of relatively low alpha and beta diversity. KW - community assembly KW - individual-based model KW - intraspecific trait variation Y1 - 2018 U6 - https://doi.org/10.1111/oik.05567 SN - 0030-1299 SN - 1600-0706 VL - 128 IS - 3 SP - 441 EP - 455 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Dalleau, Mayeul A1 - Kramer-Schadt, Stephanie A1 - Gangat, Yassine A1 - Bourjea, Jerome A1 - Lajoie, Gilles A1 - Grimm, Volker T1 - Modeling the emergence of migratory corridors and foraging hot spots of the green sea turtle JF - Ecology and evolution N2 - Environmental factors shape the spatial distribution and dynamics of populations. Understanding how these factors interact with movement behavior is critical for efficient conservation, in particular for migratory species. Adult female green sea turtles, Chelonia mydas, migrate between foraging and nesting sites that are generally separated by thousands of kilometers. As an emblematic endangered species, green turtles have been intensively studied, with a focus on nesting, migration, and foraging. Nevertheless, few attempts integrated these behaviors and their trade‐offs by considering the spatial configurations of foraging and nesting grounds as well as environmental heterogeneity like oceanic currents and food distribution. We developed an individual‐based model to investigate the impact of local environmental conditions on emerging migratory corridors and reproductive output and to thereby identify conservation priority sites. The model integrates movement, nesting, and foraging behavior. Despite being largely conceptual, the model captured realistic movement patterns which confirm field studies. The spatial distribution of migratory corridors and foraging hot spots was mostly constrained by features of the regional landscape, such as nesting site locations, distribution of feeding patches, and oceanic currents. These constraints also explained the mixing patterns in regional forager communities. By implementing alternative decision strategies of the turtles, we found that foraging site fidelity and nesting investment, two characteristics of green turtles' biology, are favorable strategies under unpredictable environmental conditions affecting their habitats. Based on our results, we propose specific guidelines for the regional conservation of green turtles as well as future research suggestions advancing spatial ecology of sea turtles. Being implemented in an easy to learn open‐source software, our model can coevolve with the collection and analysis of new data on energy budget and movement into a generic tool for sea turtle research and conservation. Our modeling approach could also be useful for supporting the conservation of other migratory marine animals. KW - connectivity KW - corridors KW - individual-based model KW - migration KW - movement KW - sea turtle Y1 - 2019 U6 - https://doi.org/10.1002/ece3.5552 SN - 2045-7758 VL - 9 IS - 18 SP - 10317 EP - 10342 PB - Wiley CY - Hoboken ER -