Why "Managed relocation" and not "Assisted migration" or "colonization"

Author: Jessica Hellmann

There is a growing scientific literature about the role that humans might play in helping species move to new locations under climate change.  Colleagues and I first wrote about the idea in 2007 in an article in Conservation Biology called, "A framework for debate of assisted migration in an era of climate change." The idea is that humans could help species that are limited in their ability to move or shift geographically under climate change. These limitations could arise from human land uses that are incompatible with species movement (think: agriculture for a forest-dwelling species) or natural restrictions on species dispersal (think: small, walking beetle populations moving hundreds of miles).

And moving is thought to be the primary way that species respond to climate changes--some individuals disperse (fly, walk, or disperse their seeds) to locations that are newly suitable and other populations die-out where conditions become unsuitable. That's what happened to many species (but not all) when the climate has changed (naturally) in the past. But this time is different because the climate is changing very rapidly (and it's hard for many species to move quickly) and lots of human activities stand in the way (such as urban development).  So maybe people could step in and help put species that are strongly affected by climate change where they need to go. Now, this has lots of potential problems associated it with it, but that's not the topic of my blog today.

Today I'm talking about terminology.  Soon after we wrote our Conservation Biology paper, my colleagues and I were criticized for using "assisted migration."  For one, it sounds like something that birds do in the winter, at least that's what some journalists thought. (In fact, "migration" is a term that paleoecologists use to describe changes in tree species' distributions during the past ice age, but that doesn't appear very high in the list of definitions at Webster's.) Second, "assisted" implies something positive, something helpful, and though the intentions of the activity might be good, it's not the business of science to judge an action without studying it first.  So these are good points.

Next, we convened a meeting of experts in fields closely related to climate change, conservation, and invasion biology, and we asked them what this idea should be called. There were some excellent people at that meeting: ecologists, leaders of natural resource agencies, economists, ethicists, and even the late Steve Schneider (see The group came up with the term "managed relocation." This term avoids the problems of assisted migration and has the added--and very important--benefit of including all of the steps that one might take in helping a species move and establish in a new location. These steps include withdrawing individuals from source populations, placing those individuals in the target (new) location, fostering young populations to help them flourish, monitoring those populations over time to see how their doing, and, even, jumping in to try to manage or undo an introduction that has gone awry (such as being too successful and too harmful to other species in the introduced region). We MUST do these later things if we are going to think about this idea in a responsible way.

There's still another term out there--"assisted colonization."  This word was first used in articles by Hunter (2007, Cons Bio 21: 1356) and Hoegh-Guldberg et al. (2008, Science 321: 345) to avoid the confusion of "migration" and focus on the process of population establishment. But this term runs the risk of being pretty normative (see above about positive connotation), and it does not include all of the stuff after colonization that should be part of a responsible introduction attempt.

So what about this vocab mess?  My preference is for managed relocation (though it doesn't really roll off your tongue, does it?).  I think that we can use assisted migration and assisted colonization to refer to managed relocation as well, but we need to be extremely careful not to judge this idea before it's been well tested, and we MUST think of this strategy as composed of multiple steps with careful assessment and execution at each step along the way, including steps after colonization.

I must say, however, that it is extremely exciting to see this literature growing, whatever terms emerging authors choose to use.