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Global warming will cause plants and animals to migrate

A new study estimates that animals and plants will have to migrate, on average, nearly a quarter of a mile each year to keep up with shifting climate belts caused by global warming.

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Globally, ecosystems will have to migrate at an average pace of nearly a quarter of a mile each year to keep up with shifting climate belts. That varies with habitat. Tropical and subtropical coniferous forests need only shift at a rate of roughly 260 feet a year to keep pace. Mangrove forests, on the other hand, would have to shift at a rate of more than half a mile a year to keep up -- highly unlikely given the unique conditions they require to thrive.

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Mangroves "are not just rich in species, but they perform ecosystem services," says Lisa Graumlich, director of the University of Arizona's School of Natural Resources and the Environment. They help stabilize coastlines by sapping waves of energy, and they serve as nurseries for fish and shellfish on which coastal communities rely either as sources of food for subsistence living or as resources for commercial fishing.

While several ecologists hail Loarie's team's effort as significant, some say the work needs to expand to also take changes in rain and snowfall projections into account. Even then, the effect on some organisms can be counterintuitive.

Duke University ecologist Robert Jackson points out, for instance, that recent studies have shown that some ecosystems are more resilient than people previously thought. He cites a study in Tennessee, where researchers at the Oak Ridge National Laboratory divided an area of woods into three plots -- one grew under existing conditions, one was subjected to drought conditions by channeling water to a third plot, simulating excessive rainfall.

The experiment, which lasted more than 10 years, found that mature trees in the stressed plots showed little change. Instead, the biggest effects were on saplings in the understory, suffered the ill effects of drought far more severely than the mature trees.

"That was a real surprise; that's a severe drought to do that for a decade," Dr. Jackson says. "When organisms are established and long-lived as adults, they are much more capable of hanging on and surviving" than they are at earlier stages of development.

Indeed, the research team notes that their work doesn't account for how individual species might respond to the changes; instead, it refers to the speed of movement and what that speed implies for how long a particular patch of the globe will experience a given climate regime. So the numbers they give are relative measures of the pace of change rather than a hard and fast set of predictions.

Still, the numbers are sobering. The team, whose work appeared in Wednesday's edition of the journal Nature, estimates that plants covering nearly 29 percent of the globe's surface would have to migrate far faster than they did as climate changes coming out of the last Ice Age, if global warming proceeds as the IPCC's business-as-usual scenario plays out. Indeed, greenhouse-gas emissions have exceeded that BAU pace during the past decade.

Put another way, the researchers calculate that by the end of the century, fewer than 10 percent of today's terrestrial conservation areas will still experience today's climate somewhere inside their borders.

In the end, the approach Loarie and his team have devised "gives us a rational, transparent tool for altering us to where we need to think about investments" in land for conservation, Dr. Graumlich says.

Up to this point, there is "a wonderful hubris we feel about conservation -- that if we could just national park systems or get more land into conservation easements that we're on a solution path that will work," she says. "But climate change changes that game forever. We no longer can take a big fat Sharpie and make a circle on a map. We have to think about conservation in a much more dynamic way."

[Editor's note: The original version misspelled Dr. Loarie's surname in some instances.]

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