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Scientists debate the pros and cons of managed relocation to save species affected by climate change

C·I·B team member Professor Dave Richardson and a group of American scientists have developed a new tool for identifying situations when a fairly radical conservation strategy (involving the deliberate movement of species to new localities to improve their chances of survival) could be seriously considered.

Dave Richardson is the lead author of a new paper that describes a ground-breaking tool designed to help policy makers determine when and how to use an environmental strategy known as “managed relocation.”

The research was published online on 9 June 2009 in Proceedings of the National Academy of Sciences of the United States of America (PNAS). It debates whether and when it could be feasible to relocate plants, animals and other organisms whose habitats, many of them already compromised by other human-mediated factors such as invasive species, are threatened by rapid climate change.

“Managed relocation”, also known as “assisted migration” or “assisted colonization” is a strategy that involves moving species into new, more accommodating habitats where they are not currently found.

The tool developed by the team provides a system for individually scoring a proposed relocation based on key social and ecological criteria. This includes how much is known about the biology, geographical distribution and the ecological uniqueness of the species and the habitat to which it is being moved, how easy the species is to catch, move and propagate, its cultural importance and the financial impact.

It is designed to provide a transparent way to expose the risks, trade-offs and costs involved in using managed relocation — considerations that are often absent from decision-making on natural resources.

A butterfly and two tree species in North America were used as examples to illustrate the very complex range of issues that need to be considered.

“We hope that the tool will help to reduce the polarity that has emerged in the debate on whether managed relocation should be added to the conservationist's toolbox,” says Richardson.

The system was developed by the multi-disciplinary Working Group on Managed Relocation, partially funded by the National Science Foundation (NSF) and the Cedar Tree Foundation in the USA. The working group, of which Richardson was part, also includes academics in many fields, including climatology, ecology, ethics and law, from several North American universities, including Brown University, Stanford University, the University of British Columbia, the University of California (Berkeley and Davis campuses), and the University of Notre Dame. Managers and decision-makers from various federal and state conservation agencies and NGOs in North America are also in the group.

“Scientists are, for the first time, objectively evaluating ways to help species cope with rapidly changing climate and other environmental threats by implementing strategies that were considered too radical for serious consideration as recently as five or ten years ago,” explains Richardson, one of the world's leading minds on matters pertaining to invasive species.

“Our decision-making tool is ground-breaking because managed relocation has traditionally been categorically eschewed by scientists for fear that relocated species would harm receiving habitats by reproducing wildly out of control, causing extinctions of local species,” says Richardson, who cites the way in which invasive alien trees have reduced water production from mountain catchments in the Western Cape as an example of the damage that translocation can do.

“The results of intentional and accidental introductions of species into new habitats have taught us a great deal about the implications of moving organisms to new habitats,” says Richardson. “Nevertheless, predictions of whether introduced species will ‘take’ in new areas and their likely impacts will always involve risks and uncertainty. But, we definitely can make informed predictions with stated bounds of uncertainty.”

Managed relocation is hardly the only controversial adaptation strategy currently being considered by scientists. Others include fertilizing the oceans to increase their absorption of greenhouse gases and thereby reduce climate change, conserving huge migratory corridors that may extend thousands of kilometres, and preserving the genetic diversity of threatened species in seed banks.

Read the paper in Proceedings of the National Academy of Sciences of the United States of America.

The transformation of landscapes by agriculture, urbanization and other forms of land use has severely limited the capacity of species to track climate change by migrating to new habitats. Many conservation strategies are being implemented to conserve species in increasingly fragmented habitats. In some cases, where more standard conservation measures fail or are impractical, threats of diminished ecosystem services or extinction driven by climate change (in concert with other threats) could be reduced by intentionally moving species from current areas of occupancy to sites where the probability of future persistence is predicted to be higher. The recent PNAS paper proposes a framework for objectively considering this conservation strategy.

Photo D.M. Richardson

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