Article

When can nuisance and invasive species control efforts backfire

Department of Natural Resources, Cornell University, Ithaca, New York 14853, USA.
Ecological Applications (Impact Factor: 4.09). 09/2009; 19(6):1585-95. DOI: 10.1890/08-1467.1
Source: PubMed

ABSTRACT

Population control through harvest has the potential to reduce the abundance of nuisance and invasive species. However, demographic structure and density-dependent processes can confound removal efforts and lead to undesirable consequences, such as overcompensation (an increase in abundance in response to harvest) and instability (population cycling or chaos). Recent empirical studies have demonstrated the potential for increased mortality (such as that caused by harvest) to lead to overcompensation and instability in plant, insect, and fish populations. We developed a general population model with juvenile and adult stages to help determine the conditions under which control harvest efforts can produce unintended outcomes. Analytical and simulation analyses of the model demonstrated that the potential for overcompensation as a result of harvest was significant for species with high fecundity, even when annual stage-specific survivorship values were fairly low. Population instability as a result of harvest occurred less frequently and was only possible with harvest strategies that targeted adults when both fecundity and adult survivorship were high. We considered these results in conjunction with current literature on nuisance and invasive species to propose general guidelines for assessing the risks associated with control harvest based on life history characteristics of target populations. Our results suggest that species with high per capita fecundity (over discrete breeding periods), short juvenile stages, and fairly constant survivorship rates are most likely to respond undesirably to harvest. It is difficult to determine the extent to which overcompensation and instability could occur during real-world removal efforts, and more empirical removal studies should be undertaken to evaluate population-level responses to control harvests. Nevertheless, our results identify key issues that have been seldom acknowledged and are potentially generic across taxa.

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Available from: Elise F Zipkin, Feb 26, 2015
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    • "v www.esajournals.org with high per capita recruitment rates in which harvest elicits a strong increase in abundance when maturation rates are fixed (Zipkin et al. 2009). However, the dampening of overcompensation by density-dependent maturation does not occur universally—for example, even strong plasticity may have little effect when removal efforts target adults, a common strategy in population control (Brooks and Lebreton 2001), or when competition among juveniles limits maturation (Fig. 2D). "
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    • "For example, if we think of α i as the natural survival rates then the population model (3) is a special case of (46). If we allow α i to include additional factors such as harvesting rates then (46) is an extension of the model in [38] (with a Beverton-Holt recruitment function) in the sense that the competition coefficients β i,n , γ i,n , c i,n may be nonzero as well as time-dependent. "
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