My Bookmarks on Science & Technology, Climate Change, Astrobiology, Genetics, Evolution

August 22, 2009 – Original Source: Canoe News, Canada, by Bob Weber

Climate change is already having a dramatic effect on plants in the High Arctic, turning the once rocky tundra a deep shade of green and creating what could be another mechanism speeding up global warming.

In a new study to be published in the November issue of the journal Ecology, University of British Columbia geographer Greg Henry has, for the first time, confirmed that rapidly rising temperatures in the Arctic are creating major changes in the plants that live there.

“It’s happening so quickly,” says Henry.

Henry first came to Alexandra Fiord on the east coast of Ellesmere Island in the 1980s to examine plants growing there. He found a harsh landscape covered with tiny Arctic willows, heather, dryas and blueberries, none taller than 10 centimetres.

Since those days, the average temperature in the area has increased by about 2.5 C – “an extremely rapid change,” says Henry.

Those warmer temperatures are making a difference.

Henry says the total amount of plant material above the ground has doubled. In wetlands, that mass is at least three times what it was in the early 1980s. Plants that barely reached researchers’ ankles now tickle their shins.

Below ground in wetland areas, researchers found 10 times as much biomass.

“That’s an extremely rapid change,” says Henry. “That’s just unbelievable.”

The changes were even more apparent where the land had been disturbed by erosion and sinkholes caused by melting permafrost.

Other evidence corresponds with his findings. The burgeoning shrub population can be spotted on satellite photos. And Dene and Inuit have been saying for years that the tundra is growing bushier.

There are other effects as well.

“If you increase the temperature, the plants respond by growing faster,” Henry says. “The leaves come out earlier, the flowers come out earlier, they set seeds earlier. The timing of things is sped up.”

The consequences of those changes, however, are still unclear.

“What’s going to be the end point here?” Henry asks. “(Are) all parts of the system going to be able to adapt to the extremely rapid change in temperature?”

The range for large grazing animals such as muskox and caribou is almost certain to change.

They may welcome the more luxuriant summer growth. But taller shrubs may crowd out lichens and mosses, which muskox and caribou depend on for winter browse.

There could also be more ominous results.

Henry’s study is restricted to Alexander Fiord. But his findings there closely match results from a global experiment that Henry co-ordinated on how warmer temperatures would affect tundra.

That means what’s happening on Ellesmere Island could well be happening on tundra around the circumpolar world.

And if that is the case, Henry said the new, denser, shrubbier tundra could speed up global warming even further simply because that vegetation is darker and absorbs more solar energy. Previous studies have suggested that a global spread of thicker plant growth on the tundra could have the same effect as doubling the amount of carbon dioxide in the atmosphere.

Henry said he expects other researchers to soon start reporting results from similar experiments in other parts of the world.

Reports on how global warming is shrinking the Arctic ice cap are increasingly common. Henry said it could be just as important to keep track of how the climbing temperatures at the top of the world are affecting landscapes.

“There’s lots of press every September when NASA comes out with the latest minimum sea ice measurements and assessments. That gets big play, but no one ever hears about tundra.”

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