Wednesday , June 16 2021

Climate change can worsen fires



According to AFP
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Mortal fires such as raging in northern and southern California have become more common in the whole state and around the world in recent years. AFP talked to scientists about the ways in which climate change can worsen them.

Other factors have also contributed to the increase in the frequency and intensity of major fires, including human interference in forest areas and dubious forest management.

"The patient was already sick," says David Bowman, professor of environmental biology at the University of Tasmania and an expert on the explosion. "But climate change is accelerating."

Every firefighter can tell you a recipe for "favorable fire weather": hot, dry and windy.

It is no wonder that many tropical and temperate regions devastated by a violent forest fire are those predicted in climate models to see higher temperatures and more drought.

"In addition to increasing the amount of dry and hot air, climate change – by increasing evaporation rates and drought – also creates more flammable ecosystems," notes Christopher Williams, director of environmental science at Clark University in Massachusetts.

Over the past 20 years, several droughts have been reported in California and southern Europe on a scale that was only once in their respective lifetimes.

Dry weather means more dead trees, shrubs and grass – and more fuel to fire.

"All these exceptionally dry years create a huge amount of dried biomass," said Michel Vennetier, an engineer at the French National Center for Scientific Research and Technology for Environment and Agriculture (IRSTEA). "It's the perfect combustible agent."

What is worse, new species better suited to semi-arid conditions appear in their place.

"Plants that like moisture have disappeared, replaced by more flammable plants that can withstand dry conditions such as rosemary, wild lavender and thyme," said Vennetier. "Change happens quite quickly."

With increasing mercury and less rain, trees and shrubs with strained water throw roots deeper into the soil, sucking out every drop of water so that they can nourish leaves and needles.

This means that moisture in the ground, which could have contributed to the slowing down of the sweeping fire through the forest or garrigue, is no longer there.

In the temperate zone in the northern hemisphere, the fire period was mostly short-lived – in July and August.

"Currently, the fire-prone period lasts from June to October," IRSTEA scientist Thomas Curt, referring to the Mediterranean basin said.

In California, which has recently appeared after a five-year drought, some experts say that there is no season at all – fires can happen throughout the year.

"The warmer, the more thunders," said Mike Flannigan, a professor at the University of Alberta in Canada and director of the Western Partnership for Wildland Fire Science.

"Especially in the northern areas, which translates into more fires."

At the same time, he noticed that 95 percent of fires around the world were started by people.

Normal weather conditions in North America and Eurasia depend largely on the powerful high-altitude air currents – produced by the contrast between polar and equatorial temperatures – known as the air stream.

But global warming has raised the temperature in the Arctic twice as fast as the global average, weakening these currents.

"We're seeing more extreme weather because of what we call blocked ridges, which is a high pressure system where the air is drowning, getting hotter and drier," said Flannigan.

"Firefighters have known for decades that they are favors."

Climate change not only increases the likelihood of fires, but also their intensity.

"If the fire becomes too intense," as it is now in California, and in Greece last summer – "there is no direct way to stop it," Flannigan said. "It's like spitting on a bonfire."

As the temperature increased, the beetles moved north into the boreal forests of Canada, wreaking havoc – and killing trees – along the way.

"Bursts of bark beetles temporarily increase the flammability of the forest, increasing the amount of dead material, such as needles," Williams said.

Globally, forests occupy about 45 percent of terrestrial carbon dioxide and consume a quarter of greenhouse gas emissions.

But when forests die and burn, some of the carbon is released back into the atmosphere, contributing to climate change in the wrong loop that scientists call 'positive feedback'.


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