Wildfires almost always need a spark to ignite, whether it’s lightning, arson, or a car’s hot exhaust pipe touching dry vegetation.
In France’s historic summer wildfires, authorities blamed a brush-clearing machine being operated around a high-voltage power line. Spanish investigators concluded that sparks from heavy machinery were behind major blazes there.
But scientists say those findings only explain how Europe’s historic wildfires began, not why they grew into the megafires that have devastated the continent this summer.
Across Europe, a combination of human-caused climate change, insufficient planning and forests planted in ways that allow flames to spread quickly are fueling fires, say experts.
“It’s not that wildfires are magic and just start. You have to have the right climatic conditions,” said Sil management hub.
Climate change is loading forests with fuel
Scientists point to three ingredients that determine whether a wildfire will spread rapidly: the amount of vegetation available to burn, how dry that vegetation is, and the weather conditions around a fire.
“When all three of these conditions are very much fire-prone and they align, then you have this kind of fire event,” said Francesca Di Giuseppe, a fire forecast project coordinator at the European Centre for Medium-Range Weather Forecasts.
Climate change is making these conditions more common and intense. A rapid analysisfrom World Weather Attribution found global warming made the extreme weather behind Spain and France’s summer wildfires much more likely.
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One reason is a phenomenon called hydroclimatic whiplash, where ecosystems suddenly swing between wet and dry conditions.
Essentially, as the planet warms, the atmosphere holds more moisture, intensifying rainfall that fuels plant growth.
“This has created an abundance of biomass that then has rapidly dried during a sequence of heat waves,” Di Giuseppe said.
In spring, a warmer atmosphere draws water from soil and plants. Drought worsens, vegetation dries out, and landscapes become far easier to ignite. In simple terms, wet winters grow fuel, and dry springs turn that fuel into perfect kindling.
This summer, that’s meant fires breaking out almost simultaneously in France, Spain, Greece, and Turkey — all driven by the same broad pattern of heat and drought.
Making matters worse, the fires themselves add to the problem. This year’s blazes have already emitted nearly 18 million tons of planet-warming CO2, according to EU figures.
Some forests are built to burn
Once a fire begins, it can take thousands of firefighters days or weeks of effort to contain the flames. That’s partly due to the way forests have been managed over decades. Across parts of Europe, large areas have been planted as monocultures, dominated by a single species grown for quick timber.
“Some of the fires we’ve been seeing in France and Spain are in places where you have these very flammable trees which are quite fine and they often are growing close together so fire spreads really easily,” Doug Kelley, a land surface modeler at the UK Centre for Ecology and Hydrology, told DW.
More than three-quarters of the Landes de Gascogne forest in southwestern France, which is currently ablaze, contains maritime pine. Created after Napoleon III ordered the region’s marshes to be drained and planted with pine in 1857, it became Europe’s largest man-made forest.
But the pine species sheds coarse needles that blanket the forest floor, providing bountiful fuel for fires. Because the trees are of similar age and height across vast areas, they are particularly vulnerable to fast-moving fire.
Another fast-growing timber tree is the eucalyptus. In Portugal the oily species — which represents more than a quarter of the country’s forestland — burned far and wide in 2017’s deadly wildfire season.
“In some regions of Europe, farmland and lower-biomass shrubland were replaced by fire-prone conifer or eucalyptus species of higher economic profitability, increasing the risk of fire,” the European Commission wrote in a case study reporton the 2017 Portuguese wildfires.
That includes Spain, where some 3 million hectares (7.4 million acres) of former farmland and pasture were planted with fast-growing pine and eucalyptus during and after the Franco dictatorship, which lasted from 1939 to 1975.
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Preventing the next disaster
Firefighters will always play a crucial role in suppressing wildfires. But experts say reducing risk before fires start is just as important. That starts with tackling the greenhouse gas emissions driving climate change and intensifying weather extremes.
“Trying to prevent in the first place the landscape becoming so flammable is one of the most effective ways to try to avoid this kind of extreme fire behavior,” said Di Giuseppe.
Replacing monocultures with mixed forests would also go a long way. Forests with a wider variety of species are generally better able to withstand drought, windstorms, insect outbreaks, and fires, because different trees respond differently to environmental stresses.
Germany offers an instructive case for forest management. Demand for timber after World War II led to spruce being planted across mountain ranges like the Harz in former East Germany. But these monocultures proved vulnerable to drought and bark beetle infestation. Foresters are now working to convert them into mixed forests to improve resilience.
Broadleaf, deciduous trees — such as oak, beech, or maple — can also help, as they typically store more moisture than conifers. Trees with thick bark, fewer low-hanging branches, and a higher moisture content tend to be more fire-resistant.
A post-event simulation studyof Portugal’s 2017 blazes found fires that overwhelmed firefighters in pine and eucalyptus stands, with flames over four meters tall, could be contained in broadleaf forest, where flame heights dropped to under a meter and a half.
Forestry experts recommend also creating breaks between rows of trees to slow fire spread and pruning lower branches so flames can’t jump quickly to the canopy. Clearing the forest floor of incendiary leaf litter and dead wood, and using controlled burns to reduce underbrush prior to wildfire season can help too.
“We need to manage our forest well in order to avoid such big disasters from happening. So prevention, prevention, prevention,” Abruscato said.
Edited by: Jennifer Collins
