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

Stellenbosch University ecologist Prof Dave Richardson and a group of American scientists have developed a new tool to identify the 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.

Prof Richardson, Deputy Director: Science Strategy at the DST-NRF Centre of Excellence for Invasion Biology at Stellenbosch University, 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 is featured in the latest Proceedings of the National Academy of Sciences of the United States of America (PNAS). It debates whether and when it is 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 and move, 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 Prof Richardson.

“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 Prof 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 Prof 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 Prof 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.”

The system was developed by a multi-disciplinary working group partially funded by the National Science Foundation (NSF) and the Cedar Tree Foundation in the USA. The Managed Relocation Working Group, of which Prof 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 are also in the group.

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.

Link to the research article on the web: http://www.pnas.org/content/early/2009/06/09/0902327106.abstract