Amplifying plant disease risk through assisted migration

Abstract

Translocation of species, populations, or genotypes beyond their historic ranges (i.e., assisted migration [AM]) is an oft‐debated climate adaptation strategy. Well‐intentioned AM actions could alter disease dynamics for target species and recipient sites, resulting in unanticipated detrimental economic and ecological impacts. Although disease risks are occasionally mentioned in AM debates, current regulations or best practices that reduce or mitigate these complex risks are generally lacking in North America. We use the “Disease Triangle”, a foundational framework in pathology, to illustrate pathways through which AM may impact disease emergence, to identify knowledge gaps, and to suggest best practices to reduce disease risks. We highlight empirical examples in which altering pathogen distributions, host communities, and environment have historically resulted in costly and ecologically damaging diseases in plants. Although guidelines to reduce disease risks in AM are generally lacking, policies governing endangered species, invasive species, and disease management can provide starting points for a more comprehensive policy. We use examples from the United States to identify key strengths and weaknesses that can inform regulations to reduce disease risks associated with AM. We argue that consideration of disease motivates policy development that incorporates improved risk assessments, agency coordination, and accountability mechanisms.

Essay: Making the most of recent advances in freshwater mussel propagation and restoration

“…Assisted migration has been vigorously discussed by conservationists (e.g., Hoegh-Guldberg et al, 2008;Ricciardi & Simberloff, 2009;Schwartz et al, 2012;Simler, Williamson, Schwartz, & Rizzo, 2018). Assisted migration has been vigorously discussed by conservationists (e.g., Hoegh-Guldberg et al, 2008;Ricciardi & Simberloff, 2009;Schwartz et al, 2012;Simler, Williamson, Schwartz, & Rizzo, 2018).…”

“…Many plants and animals that humans have moved outside of their native ranges have had large, negative, unexpected effects (e.g., Ricciardi & Simberloff, 2009;Schwartz et al, 2012;Simler et al, 2018). Many plants and animals that humans have moved outside of their native ranges have had large, negative, unexpected effects (e.g., Ricciardi & Simberloff, 2009;Schwartz et al, 2012;Simler et al, 2018).…”

“…The third variant of introduction to meet conservation goals is assisted migration (= "managed relocation," Schwartz et al, 2012)-deliberately establishing new populations outside the historical range of the species, primarily as a response to climate change. Assisted migration has been vigorously discussed by conservationists (e.g., Hoegh-Guldberg et al, 2008;Ricciardi & Simberloff, 2009;Schwartz et al, 2012;Simler, Williamson, Schwartz, & Rizzo, 2018). Proponents argue that climate change and other factors are likely to eliminate many species from their existing ranges in this century, and that many species probably will not be able to reach suitable new ranges on their own (e.g., Hoegh-Guldberg et al, 2008;Schwartz et al, 2012).…”

“…At the same time, we know little about the impacts of establishing populations of freshwater mussels at new sites, whether on the mussel populations that already live at those sites or on other parts of the ecosystem. Many plants and animals that humans have moved outside of their native ranges have had large, negative, unexpected effects (e.g., Ricciardi & Simberloff, 2009;Schwartz et al, 2012;Simler et al, 2018). Proponents of assisted migration argue that such problems can be avoided by careful analysis before translocation (e.g., Hoegh-Guldberg et al, 2008;Schwartz et al, 2012), but these authors appear to have been thinking mainly of well-studied species such as large mammals, birds, and British butterflies.…”

“…Nevertheless, questions like those raised in Box 1 of Schwartz et al (2012) about whether and how to undertake assisted migration for freshwater mussels should be addressed now, before we are confronted with the choice between numerous, imminent climate-related extinctions and poorly planned and poorly executed emergency actions to prevent these extinctions. As Simler et al (2018) noted, "These [challenges] should motivate, not deter, development of proactive comprehensive policy." The alternative-reflexive decisions either to embrace or reject assisted migration as a conservation toolis unlikely to maximize conservation benefits.…”