Individual-Based Modelling Potentials and Limitations

Individual-based modelling (IBM) is an important option in ecology for the study of specific properties of complex ecological interaction networks. The main application of this model type is the analysis of population characteristics at high resolution. IBM also contributes to the advancement of ecological theory. One of the remarkable potentials of the approach is the possibility of studying self-organization and emergent properties that arise from individual actions on higher integration levels, especially on the population level

An individual-based approach to depict the influence of the feeding strategy on the population structure of roach (Rutilus rutilus L.)

AbstractWe used an individual-based modelling strategy to simulate the growth of a roach population. Individual growth is based on food utilization, bioenergetics, spatial distribution, and seasonal influences. With this approach, it is possible to connect the animals' activity pattern with the energetic needs required for this activity. This allows investigating the role of spatial heterogeneity and individual variability for the dynamics of fish growth. The parameterisation is based on laboratory measurements and field studies performed at Lake Belau (Schleswig-Holstein, Northern Germany). The interactions of the behavioural repertoire, growth processes, and food preferences emerge in the context of a decreasing proportion of zooplankton in the food composition of simulated roach. Roach feeding on molluscs grow faster. The ontogenetic shift is related to the necessity to switch to larger prey as a consequence of the increase of energetic demands with body size

Naturkonzepte und Paradigmen in der Oekologie einige Entwicklungen

UuStB Koeln(38)-931102060 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A modeling assessment of geneflow in smallholder agriculture in West Africa

PURPOSE: Small-scale agriculture is an important issue for food security in Africa. In the context of Genetically Modified Organisms, approaches to quantify geneflow in small-scale systems are widely unexplored. We aimed at bridging this gap by contributing to the scientific discussion on the uncertainties of the cultivation of genetically modified (GM) crops in the region. The safety issue is: Would it be possible to withdraw a variety in case that unexpected and undesirable effects occur? e.g. the resistance of pests which make the variety no more useful. METHODS: We used a GIS approach to determine the location of maize cultivation sites, field geometries and applied a model for the calculation of geneflow scenarios. RESULTS: The data revealed that the given cropping density provides optimal conditions for transgene spread, potentially limiting the possibility for coexistence between GM and non-GM fields. On average, we found about 60 fields within a nearest distance of 100 m, and cropping density of 56 fields per square kilometer. The resulting cross-pollination rate from the single GM field into the neighbouring conventional fields was estimated to be about 0.12%. CONCLUSIONS: GM varieties if introduced could remain in cultivation even if their admission has expired or has been retracted. This would be undesirable and could cause long-term, undesirable stacked combination of transgenes which cannot be tested with respect to eventual combinatory effects. These developments pose major challenges for fielder livelihoods, and conservation of maize genetic resources with potentially negative consequences for the African food export sector

Climate change drives trait-shifts in coral reef communities

Climate change is expected to have profound, partly unforeseeable effects on the composition of functional traits of complex ecosystems, such as coral reefs, and some ecosystem properties are at risk of disappearing. This study applies a novel spatially explicit, individual-based model to explore three critical life history traits of corals: heat tolerance, competitiveness and growth performance under various environmental settings. Building upon these findings, we test the adaptation potential required by a coral community in order to not only survive but also retain its diversity by the end of this century under different IPCC climate scenarios. Even under the most favourable IPCC scenario (Representative Concentration Pathway, RCP 2.6), model results indicate that shifts in the trait space are likely and coral communities will mainly consist of small numbers of temperature-tolerant and fast-growing species. Species composition of coral communities is likely to be determined by heat tolerance, with competitiveness most likely playing a subordinate role. To sustain similar to 15% of current coral cover under a 2 degrees C temperature increase by the end of the century (RCP 4.5), coral systems would have to accommodate temperature increases of 0.1-0.15 degrees C per decade, assuming that periodic extreme thermal events occurred every 8 years. These required adaptation rates are unprecedented and unlikely, given corals' life-history characteristics

The Ecological Effect of Phenotypic Plasticity - Analyzing Complex Interaction Networks (COIN) with Agent-based Models

Analyzing complex dynamics of ecological systems is complicated by two important facts: First, phenotypic plasticity allows individual organisms to adapt their reaction norms in terms of morphology, anatomy, physiology and behavior to changing local environmental conditions and trophic relationships. Secondly, individual reactions and ecological dynamics are often determined by indirect interactions through reaction chains and networks involving feedback processes. We present an agent-based modeling framework which allows to represent and analyze ecological systems that include phenotypic changes in individual performances and indirect interactions within heterogeneous and temporal changing environments. We denote this structure of interacting components as COmplex Interaction Network (COIN). Three examples illustrate the potential of the system to analyze complex ecological processes that incorporate changing phenotypes on the individual level: - A model on fish population dynamics of roach (Rutilus rutilus) leads to a differentiation in fish length resulting in a conspicuous distribution that influences reproduction capability and thus indirectly the fitness. - Modeling the reproduction phase of the passerine bird Erithacus rubecula (European Robin) illustrates variation in the behavior of higher organisms in dependence of environmental factors. Changes in reproduction success and in the proportion of different activities are the results. - The morphological reaction of plants to changes in fundamental environmental parameters is illustrated by the black alder (Alnus glutinosa) model. Specification of physiological processes and the interaction structure on the level of modules allow to represent the reaction to changes in irradiance and temperature accurately. Applying the COIN-approach, individual plasticity emerges as a structural and functional implication in a self-organized manner. The examples illustrate the potential to integrate existing approaches to represent detailed and complex traits for higher order organisms and to combine ecological and evolutionary aspects.JRC.G.4-Maritime affair

The birds of Gongoni Forest Reserve, South Coast, Kenya

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Implications of GM crops in subsistence-based agricultural systems in Africa

Africa has deep contentions on the use of GM crops in agriculture, similar to those found in Europe and elsewhere. However, it is apparent that the debate is most protracted on the continent with two entrenched viewpoints i.e. the pro-GMO and anti-GMO groups. The challenge for an acceptable consensus is attributable to a complexity of issues relative to the introduction of GM maize into small-scale farming systems that fundamentally relies on open pollinated varieties (OPVs) with broad genetic backgrounds and tolerance to diverse biotic stresses, and which is usually produced for the informal seed market. Other factors relate to the generally low capacity of African states and weak mechanisms for assessing the potential risks posed by GM crops. The lack of public awareness, participation and information sharing are additional limiting factors. These issues have weakened government and policy responses to the potential deployment of GM crops on the continent. This review draws on research-based evidence as a basis to comment on some key issues to inform the development of biosafety standards in African countries. We conclude that the potential introduction of GM crops into small-scale farming would lead to huge consequences from emerging ecological, economic and trade impacts if these issues raised are not taken into account in decisionmaking processes

Sustainable introduction of GM crops into european agriculture: a summary report of the FP6 SIGMEA research project*

In 2003, the European Commission established the principle of coexistence which refers to “the ability of farmers to make a practical choice between conventional, organic and GM-crop production, in compliance with the legal obligations for labelling and/or purity standards” and laid down guidelines defining the context of this coexistence1. In order to determine what is needed for the sustainable introduction of GM crops in Europe, the cross-disciplinary SIGMEA Research Project was set up to create a science-based framework to inform decision-makers. SIGMEA has (i) collated and analysed European data on gene flow and the environmental impacts of the major crop species which are likely to be transgenic in the future (maize, rapeseed, sugar beet, rice, and wheat), (ii) designed predictive models of gene flow at the landscape level, (iii) analysed the technical feasibility and economic impacts of coexistence in the principal farming regions of Europe, (iv) developed novel GMO detection methods, (v) addressed legal issues related to coexistence, and (vi) proposed public and farm scale decisionmaking tools, as well as guidelines regarding management and governance. This publishable version of the final activity report of the FP6 SIGMEA research project, covers the fourteen major issues under investigation

Sustainable introduction of GM crops into european agriculture: a summary report of the FP6 SIGMEA research project

In 2003, the European Commission established the principle of coexistence which refers to “the ability of farmers to make a practical choice between conventional, organic and GM-crop production, in compliance with the legal obligations for labelling and/or purity standards” and laid down guidelines defining the context of this coexistence1. In order to determine what is needed for the sustainable introduction of GM crops in Europe, the cross-disciplinary SIGMEA Research Project was set up to create a science-based framework to inform decision-makers. SIGMEA has (i) collated and analysed European data on gene flow and the environmental impacts of the major crop species which are likely to be transgenic in the future (maize, rapeseed, sugar beet, rice, and wheat), (ii) designed predictive models of gene flow at the landscape level, (iii) analysed the technical feasibility and economic impacts of coexistence in the principal farming regions of Europe, (iv) developed novel GMO detection methods, (v) addressed legal issues related to coexistence, and (vi) proposed public and farm scale decisionmaking tools, as well as guidelines regarding management and governance. This publishable version of the final activity report of the FP6 SIGMEA research project, covers the fourteen major issues under investigation