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Frequent Flora Miles: Plants Can "Hop" to Distant Lands

John Roach
for National Geographic News
June 14, 2007
 
Looking for frequent flyer tips? Ask an Arctic plant.

The hardy flora rack up the miles as climate change sends them adrift in search of fresh places to put down roots, a new study says.

The finding suggests northern plants will be able to move with their northward-shifting habitats as the Earth warms.

Some researchers have feared many plants would wither under the heat, since long-distance plant travel is generally assumed to be rare and random.

"So it's good news," said Inger Greve Alsos, a biologist at the University Centre in Svalbard, a Norwegian island chain in the Arctic Ocean north of mainland Europe (Norway map).

Alsos and colleagues analyzed DNA from several thousand samples of nine plant species on Svalbard.

The plants appear to have colonized the remote islands repeatedly in the last 10,000 years, the analysis suggests. To reach the islands, most plants traveled more than 620 miles (1,000 kilometers).

She and her colleagues report the findings in tomorrow's issue of the journal Science.

Traveling Limits

There are limits, though, to where pants can find a new home in response to global warming, Alsos noted.

For one, plants need a suitable habitat to move to. If the Arctic warms too much, some cold-loving plants will have nowhere to go.

In addition, sea ice may be crucial for the Arctic plant dispersal. As it melts, plants will have fewer ways to float to more hospitable climate zones. (See "Arctic Ice Melting Much Faster Than Predicted" [May 1, 2007].)

From Russia With Leaves

For the most part, the plants in the study had come from northwestern Russia, the DNA analysis revealed.

"You can imagine, in the spring, when the big Russian rivers cause a lot of erosion along the rivers, plant material can get into the drift ice and by that get moved up to Svalbard," Alsos said.

Tons of drift ice reaches Svalbard from Russia, she noted.

Further sea ice studies will help the researchers determine if indeed it gives plants passage to the distant islands.

"If that has been important, the melting of the sea ice is a counter effect of this ability to move," Alsos noted.

Louis Pitelka, an ecologist at the University of Maryland's Center for Environmental Science, studies plant dispersal and climate change. He was not part of the new research.

Pitelka agreed that the long-distance migratory ability of plants comes as good news, but he said global warming may be happening too fast for that ability to make a difference.

"The time scales over which [the researchers] are looking are fairly long compared to what we're looking at," Pitelka said.

The Arctic plants migrated to Svalbard over at least several thousand years since the last ice age.

But with the current global warming "we're worried about a hundred years, not a thousand years," Pitelka said.

Putting Down Roots

Whether a plant can successfully "outrun" shifting climates depends more on its ability to take root in a new habitat than on its ability to travel long distances, the new study says.

"Most of the high Arctic plants that you find in Greenland or northern Russia are here [in Svalbard]," Alsos said. "But those that require a slightly warmer climate—fewer of them are here."

Currently, mean July temperature in Svalbard is between 39 and 41 degrees Fahrenheit (4 and 5 degrees Celsius).

If temperatures continue to warm, more of the warmer-weather plants are likely to take root, the researchers note.

And as long as an ecological niche is available in a warming world, the findings suggest that plants from elsewhere in the Arctic will be able to get to Svalbard.

"These are the plants that have experienced extreme range shifts also in the past," Alsos said.

It should not be assumed that plants elsewhere can successfully migrate hundreds of miles to new habitats, she cautioned.

In the Arctic, climate is the main factor that determines species distribution, she noted. Farther south, other factors become important—such as competition for nutrients and light.

So newly arrived high-Arctic plants that take root in Svalbard may soon encounter trouble from scrappier plants from farther south as they begin moving north with climate change.

"If you get a lot of these more southern species up here which might be adapted for higher competition," Alsos said, "they might outcompete the high-Arctic ones."

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