Trees Survived Ice Age Chill in Scandinavia
Baku, March 5 (AZERTAC). The last ice age hit northern Europe hard. At its height, about 20,000 to 25,000 years ago, glaciers up to 3000 meters thick covered some 6 million square kilometers of Scandinavia, the United Kingdom, Germany, Poland, and western Russia. It`s hard to believe that any trees could survive this onslaught, and most scientists assumed that Scandinavia in particular was treeless until it thawed out about 9000 years ago. Now analysis of ancient DNA has found evidence that conifer trees like pine and spruce were alive and well in Norway as early as 20,000 years ago. The findings suggest that trees may migrate slower than thought when faced with climate warming, which could have important implications for models predicting the effects of current global warming.
To try to resolve the issue, a team led by Eske Willerslev, an ancient DNA expert at the University of Copenhagen, analyzed lake sediments and pollen from the Trondelag region in central Norway and lake sediments from Andoya Island in the country`s north. As the team reports in this week`s issue of Science, it was able to recover spruce mitochondrial DNA at Trondelag in sediments dated as early as 10,300 years ago. And in sediments from Andøya Island, Willerslev and his colleagues found spruce chloroplast DNA dated to 17,700 years ago and pine chloroplast DNA dated to about 22,000 years ago, at the height of the last ice age. The team considered the possibility that young DNA might have contaminated older sediments but rejected it because lake sediments generally immobilize organic compounds in place.
The researchers also argue that their results have implications for modelling how vegetation will respond to global warming. Such models are based largely on reconstructions of past plant distributions, and many modellers have assumed that conifers spread quickly into Scandinavia after the ice sheets retreated about 9000 years ago. "Current models suggesting that conifer forests spread very fast" after a warming episode "may also be wrong," Willerslev says. It looked like trees spread quickly because they were already there, he says.
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