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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