Saturday , January 23 2021

Ten ways in which climate change can aggravate fires



PARIS: Deadly fires, such as those in the north and south of California, have become more common in the entire state and in other parts of the world in recent years. AFP spoke to scientists about ways climate change can make them worse.

Other factors have also fueled the increase in the frequency and intensity of major fires, including human degradation in wooded land and the questionable management of forests. "The patient was already ill," according to David Bowman, professor of biology of environmental change at Tasmanian University and an expert on the fire.

"But climate change is the accelerator."

Any firefighter can tell you the recipe for "favorable fire weather": hot, dry and wind.

So it is not surprising that many of the tropical and temperate areas destroyed by the increase in forest fires are those predicted in climatic models to find higher temperatures and more droughts.

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

Over the past 20 years, California and southern Europe have seen enough droughts of magnitude occurring only once a century.

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

"All these extremely dry years create a huge amount of dried biomass," said Michel Vennetier, engineer of the French Science and Technology Research for Environment and Agriculture of France (IRSTEA).

"This is an ideal fuel."

To make matters worse, new species better suited to semi-anhydrous conditions are growing in place.

"Plants that remember moisture have disappeared, replaced by more flammable plants that can withstand dry conditions such as rosemary, wild lavender and thyme," said Venice.

"Change happens pretty fast."

With increased mercury and less rainfall, the trees and shrubs with intense water send roots deeper to the ground, absorbing each drop of water that can feed the leaves and needles.

This means that moisture on earth that may have helped slow down a fire that swept through a forest or garage is no longer there.

In the vegetation of the northern hemisphere, the era of fire was historically short – in July and August, in most places.

"Today, the period that is susceptible to fires has expanded from June to October," said IRSTEA scientist Thomas Curt, referring to the Mediterranean basin.

In California, which has just emerged from a five-year drought, some experts say there is no longer a time anymore – fires can happen all year round.

"The warmer the more light you get," said Mike Flannigan, a professor at the University of Alberta, Canada, and director of the Western Partnership for Physics Science.

"Especially in the northern regions, which translates to more fires".

At the same time, he noted that 95% of the fires worldwide start from people.

The normal weather patterns over North America and Eurasia are heavily dependent on strong high-altitude air currents – generated by the contrast between polar and equatorial temperatures – known as the jet stream.

But global warming has raised Arctic temperatures two times faster than the global average, weakening these currents.

"We see more extreme weather due to what we call blocked ridges, which is a high pressure system in which the air sinks, heats and dries along the road," said Flannigan.

"Firefighters know for decades that these are favorable to fire."

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

"If the fire gets too intense," as in California at the moment, and in Greece last summer – "there is no immediate measure you can take to stop it," said Flannigan.

"It's like pushing in a fire."

With rising temperatures, the beetles have moved northwards to the northern Canada forests, causing havoc – and killing trees – along the road.

"Outbreaks of gooseberries' bark beetles temporarily increase the flammability of forests by increasing the amount of dead material, such as needles," Williams said.

At a global level, forests account for about 45% of the dry carbon of the earth and absorb one-fourth of human greenhouse gas emissions.

But as forests die and burn, part of the coal is released back into the atmosphere, contributing to climate change in a vicious loop that scientists call "positive feedback."


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