This paper was published as Bulletin of Mathematical Biology, 2009, 71 (4), pp. 863-887. It is available from http://www.springerlink.com. Doi: 10.1007/s11538-008-9385-3Metadata only entryBiological control has been attracting an increasing attention over the last two\ud decades as an environmentally friendly alternative to the more traditional chemical-based\ud control. In this paper, we address robustness of the biological control strategy with respect\ud to fluctuations in the controlling species density. Specifically, we consider a pest being\ud kept under control by its predator. The predator response is assumed to be of Holling\ud type III, which makes the system’s kinetics “excitable.” The system is studied by means\ud of mathematical modeling and extensive numerical simulations. We show that the system\ud response to perturbations in the predator density can be completely different in spatial and\ud non-spatial systems. In the nonspatial system, an overcritical perturbation of the population\ud density results in a pest outbreak that will eventually decay with time, which can be\ud regarded as a success of the biological control strategy. However, in the spatial system, a\ud similar perturbation can drive the system into a self-sustained regime of spatiotemporal\ud pattern formation with a high pest density, which is clearly a biological control failure.\ud We then identify the parameter range where the biological control can still be successful\ud and describe the corresponding regime of the system dynamics. Finally, we identify the\ud main scenarios of the system response to the population density perturbations and reveal\ud the corresponding structure of the parameter space of the system
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