Sydney, Aug 26 - The world's last remaining 'pristine' forests -- a huge swathe across Russia, Canada and other northern countries -- are under increasing threat from fire and human interference.

Increased human activity is leading to more such fires, not to speak of climate change which is only aggravating the danger in the boreal zone.

Researchers have called for urgent steps to preserve existing boreal forests to secure biodiversity and prevent the loss of this major global carbon sink.

The boreal forest comprises about a third of the world's forested area and a third of its stored carbon, covering a large proportion of Russia, Canada, Alaska and Scandinavia.

That is now changing, say researchers Corey Bradshaw and Ian Warkentin, professors at the University of Adelaide (U-A), Australia and Memorial University, Newfoundland, Canada, respectively.