A new study published by the American magazine Nature Geoscience suggests that climate change is the reason why forest fires in boreal North America have been increasing year on year.

This boreal region is characterised by its coniferous forests, its long snowy winters and its short summers and Alaska was chosen as the area of study. This is the first study to reveal that wild forest fires that are a regular feature of the 18.5 million hectares of Alaska's interior have become more severe in the last ten years.

These fires have released more carbon into the earth's atmosphere than was stored in the region's forests over the same period.

The lead author of the study is Professor of Integrated Biology Merritt Turetsky, of the University of Guelph in Ontario. "When most people think of forest fires," said Professor Turetsky, "they think of trees burning, but most of what fuels a boreal fire is plant litter, moss and organic matter in surface soils."

Professor Turetsky said that these findings were particularly worrying because about half of the world's soil carbon is locked in northern permafrost and peatland soils. For thousands of years this carbon has been slowly accumulating in ecosystems a little bit at a time, but now it is being very rapidly released through increased burning.

The concern is that this could represent a runaway climate change scenario, in which increased global warming is leading to larger and more intense fires, which release more greenhouse gases into the atmosphere, which leads to more warming and so on.

The report's co-author, Jennifer Harden a the US Geological Survey scientist, commented that this study is part of a growing body of evidence that northern systems are bearing the brunt of climate change.

Indications of global warming include longer snow-free seasons, changes in vegetation, loss of ice and permafrost and now an increase in the number of forest fires. The direct effect is to shift these northern systems from being a global carbon sink toward a carbon source.

In order to measure how much of the biomass had been burnt, researchers visited nearly 200 forest and peatland sites shortly after blazes had been extinguished. They also looked at fire records as far back as the 1950s.

Professor Eric Kasischke of the University of Maryland and another contributor to the report commented that over to past ten years the burnt area in interior Alaska had doubled, mostly due to increased burning late in the fire season.

"This is the first study to demonstrate that increases in the burnt area are clearly linked to increases in fire severity," said Professor Kasischke. "This not only impacts carbon storage, but also will accelerate permafrost and changes in forest cover."

There are also a number of health issues brought by this increase in burning. Not only can the smoke and ask cause a number of respiratory diseases. But fire emissions often contain mercury and other harmful substances.

It is important to recognise the seriousness of climate change in northern regions since wildfire will inevitably play a more and more important role in shaping the north.