Choosing plants for managed relocation - travel safely!
Written by Thomas Nuhfer
Summary
Managed relocation, where species are planted past their current range-edges is an accepted restoration (Gann et al. 2024) and conservation (Millar et al. 2007) strategy to enable the survival of slow-moving species (like plants) which cannot keep pace with climate change (Bradley et al. 2024). At the same time, managed relocation as a conservation strategy raises concerns of relocated species causing harm, if they were to act like invasive species. While some frameworks for assessing risk from range-shifting species have been proposed, it is unclear how well they balance the risk of inaction (potential losses of native species) versus the risk of action (potential unwanted harm to recipient ecosystems). Nuhfer & Bradley (2025) identified plant traits that could be used to balance these competing risks and help choose candidate species for successful managed relocation. We looked at existing traits-based risk assessments used to try to predict which non-native introduced species are likely to become invasive. We also looked through the scientific literature for plant traits considered to be useful or necessary for restoration plantings, since managed relocation is likely to be practiced in restoration contexts.
We found a high degree of overlap between traits associated with invasion risk and traits necessary for restoration. Many overlapping traits were associated with plant establishment generally, which is essential for successful managed relocation but only represents the first stage of potential invasion. Therefore, traits like generalist tendencies, high fecundity, and resistance to herbivory should not be considered ‘risky’ in managed relocation species selection, as they will exclude the species most capable of successfully establishing. At later stages of invasion, when plants spread and cause unwanted impacts, we found risk traits which are not necessary for managed relocation and are good candidates for risk assessment of range-shifting species. These traits include long distance dispersal, hybrid ability, and having invasive close relatives (e.g., in the same genus; Buonaiuto et al. 2023). Unfortunately, current guidelines for managed relocation recommend screening out risk traits that may be necessary for establishment in restoration contexts. This increases the likelihood that managed relocation will fail. Overall, we recommend integrating restoration needs to take a more risk-tolerant approach to species selection for managed relocation, since the risks of inaction and failed action (which both lead to losses of native plant populations) are high.
Take home points
Invasive species risk assessments commonly include plant traits associated with establishment, spread, and/or impact. Traits associated with establishment are critical for successful restoration and managed relocation.
Current managed relocation guidelines may be excessively risk averse, resulting in few viable species.
Risk assessment for managed relocation of native species should focus on traits which increase the likelihood of long distance spread and unwanted impacts.
Management implications
To balance risks from unwanted impacts, we must also consider the ecological risks of inaction or failed managed relocation - both will lead to losses of native species populations due to climate change.
Mitigate the risks of unwanted harm from managed relocation species by screening out species with these traits (associated with invasive plant impacts):
Long distance dispersal or many dispersal mechanisms
Invasive somewhere else, or has a close invasive relative
Polyploid or likely to hybridize in your system
Toxic or allelopathic
Difficult to remove or herbicide resistant
Climbing/smothering growth habit
Continuous seed production
Related papers
Bellemare et al., 2017; Millar et al., 2007; Wallingford et al., 2020
Keywords: native plants, range shifts, climate-smart restoration, risk, managed relocation, review