Tundra is a cold, treeless region in the Arctic, where tree growth is stunted by harsh weather.

But shrubs and willow in part of the area have been growing upward to the height of trees in the recent decades due to warming climate, scientists say.

Roughly 30 years ago, trees were nearly unknown in the region, but about 10 per cent to 15 per cent of the land in the southern part of the north-western Eurasian tundra, which stretches between Finland and western Siberia, is now covered by new tree-size shrubs, which stand higher than 6.6 feet, new research has found.

“What we have found essentially is that the growth of these shrubs is really linked to temperatures,” said study researcher Marc Macias-Fauria of Oxford University’s Biodiversity Institute.

“They are reacting to warming temperatures by growing more,” Macias-Fauria was quoted as saying by LiveScience.

The change first came to the attention of scientists, when nomadic reindeer herdsmen, the indigenous Nenets, said they were losing sight of their reindeer in the new trees, he said.

To better understand the climate dynamics associated with the increase in growth in the north-western Eurasian tundra, Macias-Fauria and team studied information from the herdsmen’s observations, temperature data, growth rings in the wood of shrubs and satellite data, including observations of how much green covers the landscape during the growing season.

The researchers, who detailed their work in the journal Nature Climate Change, found that the shrubs grew most in years with warm Julys.

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