Modelling effects of chemicals on polar bear population dynamics
Many toxic chemicals that are used in agriculture and industry are long-range transported and can accumulate in the food chain and affect top predators far from the area where they are applied. The polar bears in Greenland, Svalbard and Canada are, for example, exposed to high concentrations of PCB, brominated flame retardants (PBDEs) and Perfluoroalkyl compounds (PFAS) even though the substances have never been used in the Arctic .
The concentrations in polar bears may be high enough to affect the fecundity, behaviour, immune system, internal organs and in some cases the survival of individual bears. Data is currently available on the spatial distribution of the polar bears from satellite tagging as well as their prey, on variations in climatic conditions, on anthropogenic contaminant concentrations in the bears as well as on the toxicity of these chemicals. Data are also congregating on differences in feeding strategies of the polar bears based on Stable Isotope analysis and fatty acids. It is not known, however, how spatial and temporal variations in these factors affect the over-all dynamics of the populations.
The aim of this project is to develop individual-based and matrix models for studying the population-level effects of food availability and chemical concentrations on polar bear population dynamics in three geographically separated bear populations. The models will be validated by comparing the simulated patterns to bear distribution patterns and to patterns on individual behaviour as observed using remote sensing. A major focus of the project will be to evaluate what level of model complexity that is needed in order to generate sufficiently accurate population level patterns. This will be studied by building a hierarchy of models of gradually increasing complexity, starting with a simple non-spatial model. All models will be developed following Good Modelling Practice and will be documented using the ODD protocol. The project will significantly contribute to our understanding of the relative importance of the mechanisms that control the dynamics of the vulnerable polar bear populations.
26. 10. 2010 – I am currently implmenting an individual based model of polar bear population dynamics using the NetLogo modelling platform. This model is of simple to intermediate complexity and describes the breeding cycle of a female polar bear in detail. With this model I aim to test which modes of action of various pollutants are most harmful to the population as a whole.
10.05.2011 – Preliminary results of our non – spatial model have been presented as a poster:
Pavlova V, Nabe-Nielsen J, Dietz R, Grimm V, Svenning JC;
MODELLING POPULATION LEVEL EFFECTS OF CHEMICAL CONTAMINATION IN POLAR BEAR POPULATIONS WITH SPECIAL REGARD TO PCBS: AN INDIVIDUAL-BASED APPROACH
at AMAP conference: The Arctic as a Messenger for Global Processes, 4 – 6. May 2011, Copenhagen
Abstract can be found at: http://amap.no/Conferences/Conf2011/programme.html