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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Unveiling Human-Assisted Dispersal Mechanisms in Invasive Alien Insects: Integration of Spatial Stochastic Simulation and Phenology Models

Carrasco, L.R., Mumford, J.D., MacLeod, A., Harwood, T.D., Grabenweger, G., A.W. Leach, Knight, J.D., Baker, R.H.A. (2010) Unveiling human-assisted dispersal mechanisms in invasive alien insects: integration of spatial stochastic simulation and phenology models. Ecological Modelling. 221, 2068-2075. doi:10.1016/j.ecolmodel.2010.05.012.

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Abstract

Capturing the spread of biological invasions in heterogeneous landscapes is a complex modelling task where information on both dispersal and population dynamics needs to be integrated. Spatial stochastic simulation and phenology models have been rarely combined to facilitate such integration in order to assist on the study of human-assisted long-distance dispersal events.

Here we develop a process-based spatially explicit landscape extent simulation model that considers the spread and detection of invasive insects. Natural and human-assisted dispersal mechanisms are modelled with an individual-based approach using negative exponential and negative power law dispersal kernels and gravity models. The model incorporates a phenology submodel that uses daily temperature grids for the prediction and timing of the population dynamics in each habitat patch. The model was applied to the study of the invasion by the important maize pest Western corn rootworm (WCR) Diabrotica virgifera ssp. virgifera in Europe. We parameterised and validated the model using maximum likelihood and simulation methods from the historical invasion of WCR in Austria.

WCR was found to follow stratified dispersal where international transport networks in the Danube basin played a key role in the occurrence of long-distance dispersal events. Detection measures were found to be effective and altitude had a significant effect on limiting the spread of WCR. Spatial stochastic simulation combined with phenology models, maximum likelihood methods and predicted versus observed regression showed a high degree of flexibility that allowed capturing the salient features of WCR spread in Austria. This modelling approach is useful because allows to fully exploit the limited and heterogeneous information regarding the population dynamics and dispersal of harmful non-indigenous species.

Keywords

biological invasions, biosecurity, pest risk analysis, policy analysis, risk management

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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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Dispersal Kernels of the Invasive Alien Western Corn Rootworm and the Effectiveness of Buffer Zones in Eradication Programmes in Europe

Carrasco, L.R., Harwood, T.D., Toepfer, S., Levay, N., Kiss, J., Baker, R.H.A., MacLeod, A., Mumford, J.D., Knight, J.D. (2010) Dispersal kernels of the invasive alien Western Corn Rootworm and analysis of the effectiveness of focus and safety zones in eradication programmes in Europe. Annals of Applied Biology. 156, 63-77. doi:10.1111/j.1744-7348.2009.00363.x.

Annals of Applied Biology

Abstract

Europe, is attempting to contain or, in some regions, to eradicate the invading and maize destroying western corn rootworm. Eradication and containment measures include crop rotation and insecticide treatments within different types of buffer zones surrounding new introduction points. However, quantitative estimates of the relationship between the probability of adult dispersal and distance from an introduction point have not been used to determine the width of buffer zones. We address this by fitting dispersal models of the negative exponential and negative power law families in logarithmic and non-logarithmic form to recapture data from nine mark-release-recapture experiments of marked western corn rootworm adults from habitats as typically found in the vicinity of airports in southern Hungary in 2003 and 2004. After each release of 4,000 to 6,300 marked western corn rootworm, recaptures were recorded three times using non – baited yellow sticky traps at 30 to 305 m from the release point and sex pheromone-baited transparent sticky traps placed at 500 to 3500 m.  Both the negative exponential and negative power law models in non-log form presented the best overall fit to the numbers of recaptured adults (1% recapture rate). The negative exponential model in log form presented the best fit to the data in the tail. The models suggested that half of the dispersing western corn rootworm adults travelling along a given bearing will have travelled between 117 to 425 m and 1% of the adults between 775 to 8250 m after one day. An individual-based model of dispersal and mortality over a generation of western corn rootworm adults indicated that 9.7 – 45.3 % of the adults would escape a focus zone (where maize is only grown once in three consecutive years) of 1 km radius and 0.6 – 21 % a safety zone (where maize is only grown once in two consecutive years) of 5 km radius and consequently current EC measures are inadequate for the eradication of WCR in Europe. Whilst buffer zones large enough to allow eradication would be economically unpalatable, an increase of the minimum width of the focus zone from 1 km to 5 km and the safety zone from 5 km to 50 km would improve the management of local dispersal.

Keywords

biosecurity, chrysomelidae, coleoptera, diabrotica virgifera ssp. virgifera, dispersal kernel, equivalent attraction radius, pest risk analysis

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