Identifying Species Conservation Strategies to Reduce Disease‐Associated Declines

Abstract

Emerging infectious diseases (EIDs) are a salient threat to many animal taxa, causing local and global extinctions, altering communities and ecosystem function. The EID chytridiomycosis is a prominent driver of amphibian declines, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). To guide conservation policy, we developed a predictive decision-analytic model that combines empirical knowledge of host-pathogen metapopulation dynamics with expert judgment regarding effects of management actions, to select from potential conservation strategies. We apply our approach to a boreal toad (Anaxyrus boreas boreas) and Bd system, identifying optimal strategies that balance tradeoffs in maximizing toad population persistence and landscape-level distribution, while considering costs. The most robust strategy is expected to reduce the decline of toad breeding sites from 53% to 21% over 50 years. Our findings are incorporated into management policy to guide conservation planning. Our online modeling application provides a template for managers of other systems challenged by EIDs.

Estimating the probability of movement and partitioning seasonal survival in an amphibian metapopulation

“…Information from the current study provides the first empirical estimates of the probability of breeding dispersal and confirms the simulation output (Converse et al 2016, Gerber Fig. This supports the applicability of published models to guide the selection of management actions for conservation (Gerber et al 2017). Spread of Batrachochytrium dendrobaditis (Bd) in two drainages, Chaffee County, Colorado, USA.…”

“…However, identifying and reducing the most significant sources of uncertainty are critical in determining the best strategy to apply given conservation and stakeholder goals (Moore and Runge 2012). For example, recent models designed to identify optimal management strategies for boreal toads (Gerber et al 2017) were based partly on simulations using empirically derived colonization estimates that were independent of distance (Converse et al 2016). Simulations were used because estimates of breeding dispersal did not exist.…”

“…Movement is critical to species persistence because it strongly influences characteristics related to extinction risk and animal conservation, such as gene flow (Ovaskainen and Hanski 2001, Smith and Green 2006, Pittman et al 2014). Such probabilities are also useful in understanding host-pathogen (Gaidet et al 2010) and native-invasive species interactions (e.g., Phillips et al 2008), and to evaluate proposed management actions (Gerber et al 2017). Such probabilities are also useful in understanding host-pathogen (Gaidet et al 2010) and native-invasive species interactions (e.g., Phillips et al 2008), and to evaluate proposed management actions (Gerber et al 2017).…”

“…For example, the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) is a lethal pathogen that affects populations of amphibians on a global scale and for which management options are underdeveloped (Garner et al 2016). Quantifying the potential for amphibian movements (and thus disease, as vectored by hosts), and identifying potential routes, will reduce key uncertainties and inform the application of disease and habitat management strategies (e.g., Converse et al 2016, Gerber et al 2017. Quantifying the potential for amphibian movements (and thus disease, as vectored by hosts), and identifying potential routes, will reduce key uncertainties and inform the application of disease and habitat management strategies (e.g., Converse et al 2016, Gerber et al 2017.…”

Risk aversion and uncertainty create a conundrum for planning recovery of a critically endangered species

“…In particular, breaking a decision problem down into subcomponents, which can then be approached and solved with the most appropriate tools, is a key advantage of decision analysis (Gregory et al, 2012). We then implemented formal elicitation methods to estimate parameters, an approach increasingly used in the management of threatened species (e.g., Gerber et al, 2018;McBride et al, 2012;Runge et al, 2011;Runge, Rout, Spring, & Walshe, 2017). Nest success is the result of a sequential chain of events, each influenced by management actions to a different extent.…”