Subpopulation Triage: How to Allocate Conservation Effort among Populations

Abstract

Threatened species often exist in a small number of isolated subpopulations. Given limitations on conservation spending, managers must choose from strategies that range from managing just one subpopulation and risking all other subpopulations to managing all subpopulations equally and poorly, thereby risking the loss of all subpopulations. We took an economic approach to this problem in an effort to discover a simple rule of thumb for optimally allocating conservation effort among subpopulations. This rule was derived by maximizing the expected number of extant subpopulations remaining given n subpopulations are actually managed. We also derived a spatiotemporally optimized strategy through stochastic dynamic programming. The rule of thumb suggested that more subpopulations should be managed if the budget increases or if the cost of reducing local extinction probabilities decreases. The rule performed well against the exact optimal strategy that was the result of the stochastic dynamic program and much better than other simple strategies (e.g., always manage one extant subpopulation or half of the remaining subpopulation). We applied our approach to the allocation of funds in 2 contrasting case studies: reduction of poaching of Sumatran tigers (Panthera tigris sumatrae) and habitat acquisition for San Joaquin kit foxes (Vulpes macrotis mutica). For our estimated annual budget for Sumatran tiger management, the mean time to extinction was about 32 years. For our estimated annual management budget for kit foxes in the San Joaquin Valley, the mean time to extinction was approximately 24 years. Our framework allows managers to deal with the important question of how to allocate scarce conservation resources among subpopulations of any threatened species.

Conservation implications should guide the application of conservation genetics research

“…This is not to say that the question is not valuable or that it may not need to be addressed in the future; it simply suggests that this particular research question should not be prioritized for limited conservation resources at this point in time. The use of our key is concordant with a recent call for conservation practitioners to employ a triage approach to the allocation of conservation resources, in the same manner that medical practitioners apply the triage approach to emergency medicine (Bottrill et al 2008, McDonald-Madden et al 2008a). …”

Quantifying drivers of population dynamics for a migratory bird throughout the annual cycle

“…Combined with decision-analytic approaches that can accommodate additional factors, such as cost, risk and uncertainty, these models can help inform strategic conservation plans that will yield greater return on investment [49]. For wood thrush, and likely many other species, our results suggest that a strategic approach to conservation should be region-specific and address the factors limiting the highest priority populations [50].…”

Unexpected outcomes of invasive predator control: the importance of evaluating conservation management actions

“…To ensure the future success of malleefowl conservation, the effectiveness of alternative management actions, such as reduction of grazing pressure by competing herbivores and prescribed burning, need also be evaluated. With data on multiple management actions, it would be possible to quantify their respective outcomes for malleefowl and prioritize which subpopulations should receive investment (McDonald-Madden, Baxter & Possingham, 2008;Joseph, Maloney & Possingham, 2009;Evans, Possingham & Wilson, 2011). Yet, even with one of Australia's most studied and managed threatened species, such a task as using empirical data is not yet possible.…”