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Climate Change Responsible for the Increased Rate of Wildfires in Alaska’s Boreal Forests

First Posted: Jul 23, 2013 12:25 PM EDT

In recent decades there has been a dramatic increase in both frequency and severity of wildfires near the Arctic Circle and in  Alaska's Yukon region the wildfire activity is higher when compared to the past 10,000 years, researchers report.

The researchers believe that climate change is accelerating the rate of wildfires in the boreal zone. Due to the wildfires more than half a million acres of land has been blackened.

The data produced by a team of scientists from the University of Illinois suggests that the frequent and powerful fires are converting the forests of the Yukon flats into deciduous woodland. And deciduous trees are more resistant to fire than the black and white spruce that made up the forests in the area.

"We reconstructed the fire history by picking charcoal fragments out of sediments preserved over thousands of years. And from what we can tell, the fire frequency at present is higher than it has been at any time in the past 10,000 years, study lead Ryan Kelly said in a press statement.

A study conducted earlier by Los Alamos National Laboratory suggested that, wildfires were responsible for warming Earth's atmosphere far more than what was thought earlier.

In the current study,  researchers worked on the data collected from the bottom of 14 deep lakes in the Yukon Flats.  They hunted for charcoal as well as pollen content from the mud samples that were retrieved.

The reason why the researchers chose this area is because it is susceptible to wildfires.  In this they are focusing on an area that is highly flammable and are also concentrating on periods of climate fluctuation that occurred during the Holocene. By understanding what happened in the past they can predict what may happen in the years to come.

Holocene is a geological epoch that began 11,700 years ago and continues to the present. The team specifically looked at the warm period of Holocene, which is called the Medieval Climate Anomaly (MCA) that occurred 1,000-500 years ago.

The current shift in character on the Yukon flats where the coniferous trees are being replaced by the deciduous trees is similar to the shift that took place during MCA. During those days, there was a rise in the average temperature in the North Atlantic region similar to the warming conditions occurring in the Arctic.

Kelly explains, "This period probably wasn't really as warm as today, definitely not as warm as it's bound to get in the future, but may be the most similar to today. There was lots of burning, almost as much as today, and the fires were particularly severe."

The researchers noticed that the shift in the composition of the tree species occurred gradually during the MCA where the conifer rich boreal forests were converted into deciduous woodlands. And this trend is continuing to the present times

Apart from this, the study also states that the occurrence of wildfires has surpassed the frequency of wildfire activity that occurred during the MCA. During the last 3,000 years the average fire frequency was nine or ten fires per thousand years. Whereas in the last 50 years, there has been an upward tick in the wildfire events, the number has doubled to 20 fires per 1000 years.

"That's like a fire every 50 years, whereas in the past it was closer to a fire every hundred years," Kelly said.

This study is important as nearly 10 percent of Earth's land is covered by boreal forests that contain a large amount of carbon in the soil.

"There is more carbon in the boreal forests than in the atmosphere," explains Kelly. "And one of the main ways that the carbon that's accumulated over thousands of years gets out of the soil is through burning."

It is this wildfire activity that is causing climate change and if this trend continues it is possible that even the deciduous forests will become highly flammable because it is after all wood and if it's dry it will eventually burn.

The researchers documented the study in the Proceedings of the National Academy of Sciences

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