Gunnar Dressler

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Gunnar Dressler

Affiliations

Helmholtz Centre for Environmental Research

Professional homepage

http://www.ufz.de/index.php?en=36650

ORCID more info

https://orcid.org/0000-0002-1769-3064

GitHub more info

No associated GitHub account.

  • since April 2017: PostDoc at the Department of Ecological Modeling, Helmholtz Centre for Environmental Research - UFZ
  • since January 2015: Member of the Junior Research Group POLISES - Global food security policies and their social-ecological side effects in regions prone to global change.
  • 2012-2017 PhD student at the Department of Ecological Modeling, Helmholtz Centre for Environmental Research - UFZ
  • 2006-2011 Diploma in Biomathematics, Ernst-Moritz-Arndt-University of Greifswald

Research Interests

  1. Dynamics of socio-ecological resource use systems
    • Pasture use in dryland grazing systems under change, effects of new technologies and policy instruments, emergence of polarization between pastoralists (e.g. in terms of livestock numbers).
    • Thresholds of disaster management performance under change, loss of manpower, the role of information as critical resource.
  2. Human decision making in agent-based models.
  3. Remote sensing and GIS.

The Land Use Competition in Drylands (LUCID) model is a stylized agent-based model of a smallholder farming system. Its main purpose is to illustrate how competition between pastoralism and crop cultivation can affect livelihoods of households, specifically their food security. In particular, the model analyzes whether the expansion of crop cultivation may contribute to a vicious circle where an increase in cultivated area leads to higher grazing pressure on the remaining pastureland, which in turn may cause forage shortages and livestock loss for households which are then forced to further expand their cultivated area in order to increase their food security. The model does not attempt to replicate a particular case study but to generate a general understanding of mechanisms and drivers of such vicious circles and to identify possible scenarios under which such circles may be prevented.

The model is inspired by observations of the Borana land use system in Southern Ethiopia. The climatic and ecological conditions of the Borana zone favor pastoralism, and traditionally livelihoods have been based mainly on livestock keeping. Recent years, however, have seen an advancement of crop cultivation as a coping strategy, e.g., to compensate the loss of livestock, even though crop yields are low on average and successful harvests are infrequent.

In the model, it is possible to evaluate patterns of individual (single household) as well as overall (across all households) consumption and food security, depending on a range of ecological, climatic and management parameters.

FIsheries Simulation with Human COmplex DEcision-making (FISHCODE) is an agent-based model to depict and analyze current and future spatio-temporal dynamics of three German fishing fleets in the southern North Sea. Every agent (fishing vessel) makes daily decisions about if, what, and how long to fish. Weather, fuel and fish prices, as well as the actions of their colleagues influence agents’ decisions. To combine behavioral theories and enable agents to make dynamic decision, we implemented the Consumat approach, a framework in which agents’ decisions vary in complexity and social engagement depending on their satisfaction and uncertainty. Every agent has three satisfactions and two uncertainties representing different behavioral aspects, i.e. habitual behavior, profit maximization, competition, conformism, and planning insecurity. Availability of extensive information on fishing trips allowed us to parameterize many model parameters directly from data, while others were calibrated using pattern oriented modelling. Model validation showed that spatial and temporal aggregated ABM outputs were in realistic ranges when compared to observed data. Our ABM hence represents a tool to assess the impact of the ever growing challenges to North Sea fisheries and provides insight into fisher behavior beyond profit maximization.

RAGE models a stylized common property grazing system. Agents follow a certain behavioral type. The model allows analyzing how household behavior with respect to a social norm on pasture resting affects long-term social-ecological system dynamics.

Under development.

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