In the face of climate change, does it make sense to use assisted migration techniques to save various species of plants, trees and animals? The answer seemed relatively simple a few years ago, but it is an increasingly controversial issue, says postdoctoral fellow and lecturer Nina Hewitt of York’s Department of Geography.
Hewitt is the lead author on “Taking Stock of the Assisted Migration Debate”, an article published in the Biological Conservation journal this fall that synthesizes the debate by looking at about 50 articles written on the subject. It is one of the journal's "most read" articles for November.
“Assisted migration is a policy that says we need to take a proactive kind of hands-on approach and help species that are slow-moving to achieve these northward or altitudinal migrations as climate belts shift, with climate change occurring at very rapid rates, beyond the species’ normal dispersal and colonization abilities. This will be further complicated by the difficulties of migration across human-dominated landscape,” says Hewitt, a Senior Fellow and postdoctoral researcher with York’s Institute for Research & Innovation in Sustainability (IRIS).
The article is part of an IRIS research project on assisted migration, invasive species and climate change, funded by the Canadian Foundation for Climate & Atmospheric Sciences.
Left: Nina Hewitt
It involves taking a species which is vulnerable to extinction in its current ecosystem and transplanting it somewhere else. “But there is a risk: the risk of invasion of the transplanted species in the community into which it is introduced,” she says. Assisted migration would involve transplanting an endangered species to a community beyond its population margin, into a whole other landscape type, and hoping it can establish itself there without being overly aggressive and taking over the already established species.
“Some of these species have no impact; they just stay there or don’t do well, or they can be really successful and create a problem where native species become extinct,” says Hewitt
Take a look at the starling, which was transplanted into North America from Europe because someone wanted all the birds from Shakespeare’s sonnets here. They’re an example of an overly successful assisted migration. “And while no one is proposing such extreme, long-distance migrations, there can still be complications,” she says. “A number of scientists, also concerned with the effects of climate change, have said this policy opens the door to some very risky issues, especially if we don’t know and can’t predict if these assisted species will become problematic in the communities to which they are introduced.”
The level of controversy that has erupted over this issue in recent years, and that it remains unresolved, surprises Hewitt. She puts it down to the fact that the impact of climate change has become clearer and more urgent, and “so the need to actually do some of these drastic, interfering, proactive measures, such as take a species and transplant it en masse somewhere else, are being pushed more openly” by some scientists. This seems to have precipitated a reaction by those who argue against assisted migration, and those voices seem to have gotten louder in the last two or three years.
Hewitt worries that the debate will become so entrenched that it will stay in a kind of paralysis with policymakers unable to either embrace or reject the policy. There needs to be a better sense of whether to adopt assisted migration in certain situations, or abandon it. “With this paper, we were hoping to highlight the different sides of the debate so that scientists and policymakers can evaluate the risks and benefits and together make some progress so we don’t get stuck in that paralysis,” she says. "Taking Stock of the Assisted Migration Debate" was co-authored with postdoctoral Fellow Nicole Klenk and several IRIS researchers.
There are risks to proceeding with assisted migration, but at the same time there may be risks associated with doing nothing. “What I found was that the debate seemed to be stuck around what we call ‘other issues’ – neither direct risks nor benefits to implementing a particular assisted migration, but rather, counter arguments to the opposite side of the debate. These counter arguments need to be distinguished from direct risks and benefits because they can’t provide justification for scrapping or adopting the policy,” says Hewitt.
She thinks a careful, case-by-case consideration of relative risks and benefits is the way to go. Before assisted migration can be considered, there has to be a reasonable benefit to migrating the species that can be assessed in relation to risk. She hopes the article will help bring much-needed focus to the debate.
By Sandra McLean, YFile writer