Accounting for Management Costs in Sensitivity Analyses of Matrix Population Models

Abstract

Traditional sensitivity and elasticity analyses of matrix population models have been used to inform management decisions, but they ignore the economic costs of manipulating vital rates. For example, the growth rate of a population is often most sensitive to changes in adult survival rate, but this does not mean that increasing that rate is the best option for managing the population because it may be much more expensive than other options. To explore how managers should optimize their manipulation of vital rates, we incorporated the cost of changing those rates into matrix population models. We derived analytic expressions for locations in parameter space where managers should shift between management of fecundity and survival, for the balance between fecundity and survival management at those boundaries, and for the allocation of management resources to sustain that optimal balance. For simple matrices, the optimal budget allocation can often be expressed as simple functions of vital rates and the relative costs of changing them. We applied our method to management of the Helmeted Honeyeater (Lichenostomus melanops cassidix; an endangered Australian bird) and the koala (Phascolarctos cinereus) as examples. Our method showed that cost-efficient management of the Helmeted Honeyeater should focus on increasing fecundity via nest protection, whereas optimal koala management should focus on manipulating both fecundity and survival simultaneously. These findings are contrary to the cost-negligent recommendations of elasticity analysis, which would suggest focusing on managing survival in both cases. A further investigation of Helmeted Honeyeater management options, based on an individual-based model incorporating density dependence, spatial structure, and environmental stochasticity, confirmed that fecundity management was the most cost-effective strategy. Our results demonstrate that decisions that ignore economic factors will reduce management efficiency.

Evaluating vital rate contributions to greater sage‐grouse population dynamics to inform conservation

“…The integration of both types of data could provide insight into population dynamics at sites where the entire life cycle has not been studied (Davis et al 2014), and be used to examine population dynamics at greater spatiotemporal scales. Furthermore, perturbation analyses such as ours based on long-term demographic studies are needed to enhance scientific rigor for prioritization of the most cost effective species conservation and management actions (Akçakaya and Raphael 1998, Cooch et al 2001, Clutton-Brock and Coulson 2002, Baxter et al 2006 …”

Optimal allocation of conservation effort among subpopulations of a threatened species: How important is patch quality?

“…As a result of this limitation, managers are often faced with the difficult decision of how to allocate their money between subpopulations of a species in order to get the best results. Furthermore, it has been shown that ignoring the cost of conservation when deciding how to manage species can lead to misdirected effort and ultimately wastes management resources (Baxter et al 2006, Wilson et al 2006. Consequently, there is a need for a decision-making approach that enables managers to make practical management decisions that use resources efficiently .…”

Robust Population Management Under Uncertainty for Structured Population Models

“…We have not addressed this issue in the present example, but it would be straightforward to rescale the perturbations ( p 1 , p 2 ) by the relative amount of variability in the parameters they are affecting, if estimates of this variability are available. A better, prospective approach would rescale the perturbations by their relative cost (ease of manipulation); an excellent example of how to do this using sensitivity analysis is given by Baxter et al (2006).…”