National Park Service


Date of this Version



Natural Resource Report NPS/NRSS/CCRP/NRR 2021/2241 / NPS 999/175141, March 2021

Also available at:

Please cite this publication as:

Karasov-Olson, A., M. W. Schwartz, J. D. Olden, S. Skikne, J. J. Hellmann, S. Allen, C. Brigham, D. Buttke, D. J. Lawrence, A. J. Miller-Rushing, J. T. Morisette, G. W. Schuurman, M. Trammell, and C. Hawkins Hoffman. 2021. Ecological risk assessment of managed relocation as a climate change adaptation strategy. Natural Resource Report NPS/NRSS/CCRP/NRR—2021/2241. National Park Service, Fort Collins, Colorado.


United States government work. Public domain material.


Executive Summary

Changing climate and introduced species are placing an increasing number of species at risk of extinction. Increasing extinction risk is increasing calls to protect species by relocating, or translocating, them to locations with more favorable biotic or climatic conditions. Managed relocation, or assisted migration, of species entails risks to both the conservation target organisms being moved as well as the recipient ecosystems into which they are moved.

Recognizing this risk, calls have been made for practitioners interested in considering a managed relocation project to engage in a serious risk assessment prior to advancing a project. We engaged a team of researchers and resource managers to create risk assessment protocols that could be used by natural resource managers within U.S. National Parks, or elsewhere, to help inform a decision of whether the risks involved in managed relocation are warranted. These protocols facilitate evaluation of the ecological risk of species managed relocation as part of planning and decision making. This is not a policy document. It neither introduces new policy, nor serves to interpret or resolve current policies regarding managed relocation (or assisted migration) as a natural resource management strategy.

We assembled a team of five university researchers and ten federal resource management researchers and staff to develop a practical management-oriented risk assessment strategy. We jointly agreed to a set of principles to guide this managed relocation risk assessment strategy. This protocol and accompanying spreadsheet would be used to help a decision-maker structure a decision process but would not strive to provide a formulaic decision output. Identifying, evaluating, and managing risk is a subjective decision that is the responsibility of the decision authority.

We began by defining the scope of this work to include moving populations or species for the purpose of conserving the target populations or species that are threatened by climate or invasive species. We also included species movements for the purpose of retaining some critical ecosystem function. We did not include management actions such as planned ecosystem re-alignment for climate change or other kinds of translocations associated with ecosystem manipulation (e.g., habitat restoration), although these protocols may be useful for some of those management actions with minor modification.

We adopted the premise that risk decisions are inherently subjective and that different aspects of risk (e.g. the risk of a moved species introducing a novel pathogen to an ecosystem, the risk of unwanted evolution in the moved species) are non-additive. Hence, our strategy is designed to encourage managers to think broadly and comprehensively about risk in order to make the best possible decision given alternate opposing risks (i.e. the risk of extinction versus the risk of causing unintended harm to other species and ecosystems in the process of trying to save a species).

We identified six major areas of risk, with a total of seventeen sub-categories. These are:

• Risks of no managed relocation action. Risk of:

o no action on the target

o no action on the recipient ecosystem

• Risks of managed relocation action to the target. Risks of:

o action on the translocated individuals

o target source population extirpation through diminished numbers

o reduced ecological functioning of the source ecosystem

o causing undesired evolution in the target

• Risks of action on non-targets in the recipient ecosystem. Risks of:

o target transmitting novel disease or associated pest

o negative competitive interactions on non-target populations

o predation, herbivory, or allelopathic effects on non-target populations o driving undesirable evolution in non-target species

• Risks of action on higher order attributes of the recipient ecosystem. Risks of:

o indirect and negative impacts on ecosystem structure

o changing ecosystem function

• Risks associated with invasion. Risks of:

o invasion within the intended recipient ecosystem

o invasion beyond recipient ecosystem

o irreversibility of the managed relocation action

• Risks associated with socio-economic values. Risks to:

o culturally or economically important species

o valued ecosystem services

For each risk category we provide guidance on risk scoring. Risk scoring is comprised of a risk rank category (low, moderate, high, very high) and a confidence score (low, medium, high). Confidence is a combined attribute of the strength of evidence and the agreement of that evidence.

The protocols are presented in an accompanying Excel spreadsheet that uses a graphical tool to allow users to visualize a composite of risk and confidence. We are adamant about not summing across risk categories. Instead, we provide a graphing tool that summarizes risk within categories. We suggest that users could find risks posed by a proposed action to be acceptable if:

1) Confidence scores are sufficient that managers feel confident that the risk assessment is informative;

2) There is no single risk category that is so high and so important as to make the project unacceptably risky; and

3) The general distribution of risk is not so high as to exceed some level of expectation that one of many potential problems could arise and lead to decision regret.

We frame this risk assessment within the context of other critical questions that need to be answered in order to proceed toward strategic planning for a managed relocation action. These include justifying ecological need, assessing technical feasibility, cost, management priority and social acceptability. If all these criteria are met, then these same protocols can be used in a multi-criteria assessment to compare across different strategic plans for managed relocation (e.g. relocation location, relocation numbers, source and husbandry of relocated individuals). We provide brief guidance on how that may be completed with no presumption of final decision determination.

Finally, in the process of developing these risk scoring protocols, we tested them on a suite of four case studies (bull trout, Karner blue butterfly, giant sequoia and Pitcher’s thistle). These are provided in this document as examples of the logic and process that we outline for assessing risk. These were, however, done without broad consultation and should be taken not as definitive risk assessments of managed relocation for these species, but as examples of how one might use our strategy for an assessment of ecological risk associated with managed relocation.