The deliberate relocation of a species to a more suitable climate, particularly when the existing location has become unsuitable due to climate change.
When the Earth shifted from icy to tropical periods in the past, fossil records show that species shifted too. Today, climate change is moving the butterflies of Europe northward — as well as holly plants in Britain.
But what happens to those that can't move, or that find major cities or highways block their way? Enter assisted migration, a sort of emergency-relief service that springs species from global warming danger zones.
—Ann McIlroy, "The New Climate Almanac: Assisted migration," The Globe and Mail, February 17, 2007
Studies on the Bay checkerspot butterfly suggest that this climate change will push the insect to extinction. The plants it depends on for food will shift their growing seasons, so that when the butterfly eggs hatch, the caterpillars have little to eat. Many other species may face a similar threat, and conservation biologists are beginning to confront the question of how to respond. The solution they prefer would be to halt global warming. But they know they may need to prepare for the worst.
One of the most radical strategies they are considering is known as assisted migration. Biologists would pick a species up and move it hundreds of miles to a cooler place.
Assisted migration triggers strong, mixed feelings from conservation biologists. They recognize that such a procedure would be plagued by uncertainties and risk. And yet it may be the only way to save some of the world's biodiversity.
—Carl Zimmer, "A Radical Step to Preserve a Species: Assisted Migration," The New York Times, January 23, 2007
There could be distinct risks for particular forest types if they are penned into particular areas by artificial human-made boundaries, with the climate gradually becoming less and less suitable for them, he cautions.
"We can help our forests to move gradually across the landscape through 'assisted migration'," Dr Kirschbaum suggests. "Without drastic cuts in Greenhouse gas emissions, it now seems that a degree of climate change is inevitable, so we need to begin to plan now to set up a series of stepping stones that will move particular forest types to the environments where they will be doing best a century or so from now."
—"Greenhouse impact on Australia's forests," M2 Presswire, January 27, 1998
There's a much older sense of the phrase assisted migration that refers to the deliberate relocation of people — especially new immigrants or the poor — to areas considered to be more suitable. Here's the earliest citation I could find for this sense:
Frankly, as I read the report, it does set out an either/or. It says we should stop aiding cities and start facilitating movement out (through) what the report calls ''assisted migration'' and what other people have called bus tickets to Phoenix — which is what it indeed entails. We've heard a lot from people in Phoenix and in Dallas who say, ''Don't give me your tired, your hungry and your poor.''
—Richard P. Nathan, "Help old cities or encourage the crowd to escape them?," The New York Times, March 15, 1981