Towards the Integration of Spread and Economic Impacts of Biological Invasions in a Landscape of Learning and Imitating Agents

Carrasco, L.R., Cook, D.C., Mumford, J.D., MacLeod, A., Knight, J.D., Baker, R.H.A. (2012) Towards the integration of spread and economic impacts of biological invasions in a landscape of learning and imitating agents. Ecological Economics. 76, 95-103. doi:10.1016/j.ecolecon.2012.02.009.

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Abstract

Invasions of harmful non-indigenous species (NIS) and their control by land managers are complex and opposing processes that generate economic costs in a dynamic and spatial fashion. Here we develop an agent-based model integrated with a spatial stochastic simulation NIS spread model where the agents (farmers) are endowed with learning and imitation capabilities. The model is applied to the case of the western corn rootworm invasion in England. We dynamically link the welfare loss of the producers to the spatial distribution of the invasion; allowing us to study the effects of control policies and farmers’ behaviour on welfare losses and the invasion process. The results show a trade-off between compliance costs and yield losses costs for different levels of control intensity, however, a laissez faire policy against the invasion would be preferred for England. When the farmers can learn from experiences and imitate each other, we find that control measures might fail completely if there is global knowledge of the burdens of compliance (e.g. through the media) and the farmers can foresee the future consequences of new actions. The effectiveness of the control program is respectively not affected or only partially affected if the farmers need to experience compliance to learn its consequences or communicate only locally. Attempts to take the pulse of negative opinions of land managers over NIS control programs and their media coverage might be a powerful predictor of the odds of failure of the programs.

Keywords

biosecurity, dispersal, diabrotica virgifera virgifera, metapopulation, invasive alien species, pest risk analysis

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Comprehensive Bioeconomic Modelling of Multiple Harmful Non-Indigenous Species

Carrasco, L.R., Mumford, J.D., MacLeod, A., Knight, J.D., Baker, R.H.A. (2010) Comprehensive bioeconomic modelling of multiple harmful non-indigenous species. Ecological Economics. 69, 1303-1312. doi:10.1016/j.ecolecon.2010.02.001.

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Abstract

Harmful non-indigenous species (NIS) introductions lead to loss of biodiversity and serious economic impacts. Government agencies have to decide on the allocation of limited resources to manage the risk posed by multiple NIS. Bioeconomic modelling has focused on single species and little is known about the optimal management of multiple NIS using a common budget. A comprehensive bioeconomic model that considers the exclusion, detection and control of multiple NIS spreading by stratified dispersal and presenting Allee effects was developed and applied to manage the simultaneous risk posed by Colorado beetle, the bacterium causing potato ring rot and western corn rootworm in the UK. A genetic algorithm was used to study the optimal management under uncertainty. Optimal control methods were used to interpret and verify the genetic algorithm solutions. The results show that government agencies should allocate less exclusion and more control resources to NIS characterised by Allee effects, low rate of satellite colonies generation and that present low propagule pressure. The prioritization of NIS representative of potential NIS assemblages increases management efficiency. The adoption of management measures based on the risk analysis of a single NIS might not correspond to the optimal allocation of resources when other NIS share a common limited budget. Comprehensive bioeconomic modelling of multiple NIS where Allee effects and stratified dispersal is considered leads to a more cost-effective allocation of limited resources for the management of NIS invasions.

Keywords

biosecurity, genetic algorithm, invasive alien species, optimal control, propagule pressure

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