Assisted migration for biodiversity

This article in the NYT deals with one of the biodiversity conservation options I have been thinking about as an adaptation policy for dealing with the effects of climate change. The radical strategy is assisted migration - moving species to climatic zones where they have a better chance of survival.

This triggers strong, mixed feelings from conservation biologists because the procedure is plagued by risk. Yet not undertaking the strategy may condemn species to inevitable extinction.
The average temperature of the planet is 1.6 degrees F higher than in 1880. Dr. Camille Parmesan, reviewed hundreds of studies on the ecological effects of climate change in this month's Annual Review of Ecology, Evolution, and Systematics. Many plant species are now budding earlier in the spring. Animals migrate earlier as well. And the ranges of many species are shifting to higher latitudes, as they track the climate that suits them.

These adjustments have occurred over the past 2 million years as the planet has swung between ice ages and warm periods. But the current bout of warming may be different as the earth was already relatively warm when it began. It’s also going to be more difficult for some species to move since when the planet warmed at the end of past ice ages, retreating glaciers left behind empty landscapes. Today’s species will face an obstacle course of cities, farms and other human settlements. Animals and plants will also have to move quickly if they are to keep up with relatively quick climatic changes.

Many conservation biologists believe that conventional strategies may help combat extinctions from global warming. Bigger reserves and corridors connecting them, could give species more room to move.

McLachlan, Schwartz and Hellmann lay out the debate in a paper to be published in Conservation Biology. Assisted migration may be the only way to save some species but biologists need to answer many questions before they can do it safely and effectively. Some questions:

Which species to move? If thousands are facing extinction, it will probably be impossible to save them all. Conservation biologists will have to make decisions about which species to try to save. Some species threatened by climate change, including polar bears and other animals adapted to very cold climates, may have nowhere to go.

Where to take them? Conservation biologists will have to identify regions where species can survive in a warmer climate. But to make that prediction, scientists need to know how climate controls the range of species today. That information is lacking. Simply moving a species is no guarantee it will be saved since many species depend on other species for their survival. In addition, a transplanted species would be an invasive one which might thrive so well that it would start to harm other species.

Perhaps assisted migration should be a measure of last resort that is used sparingly. But species migrations will occur anyway and, as species shift their ranges, some will push into preserves that are refuges for endangered species. Will some new migrants need to be eradicated?

None of these questions are simple and all are relevant.