The Washington PostDemocracy Dies in Darkness

How a devastating forest fire revealed a tree as close to fireproof as a tree can get

After a stand of cypress resisted a forest fire that burned 50,000 acres in Spain, researchers say that the plant could be used as a buffer to prevent other fires from spreading. (Bernabe Moya)
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The Moya brothers were tree experts — one was a botanist, the other an environmental engineer. But they were also tree lovers. So when a fire raged through an experimental plot of trees they were studying in the summer of 2012, their hearts sunk.

“On our way to what we knew would be a Dante-esque scene during that tragic summer, we felt deep sadness at the thought of losing a plot of such value to the conservation of biodiversity,” Bernabé Moya, the botanist, told the BBC.

Indeed, their 50,000-acre plot in Andilla, Spain looked like something out of “Inferno.” Vast expanses of oaks, pines and junipers had been reduced to ash and rubble. Once-verdant hillsides were gray-brown and barren.

[Wildfires have now burned a massive 8 million acres across the U.S.]

But amid the devastation, they saw a sign of hope: a stand of 946 Mediterranean cypress trees, each taller than a two story house, that formed a perfectly square patch of green in the scorched landscape.

Bernabe Moya and his brother Jose couldn’t believe their eyes. And when they told their colleagues about the strange phenomenon, they couldn’t believe it either.

“We will have to find out what really happened,” Raúl de la Calle of the Official Association of Technical Forest Engineers told the Madrid-based newspaper El Pais in 2012. “The cypress is not a very combustible species, but to the point that it doesn’t burn at all. … There is no such thing as a fireproof tree.”

Perhaps not. But three years later, the Moyas, along with Spanish and Italian colleagues, believe that the cypress might be as close to fireproof as a tree can get. In a study published in the Journal of Environmental Management, they discuss the tree’s remarkable resilience and argue for its use as a natural buffer that could prevent the spread of wildfires.

[A firefighter’s life, and his tragic death, on the front lines of the great Western wildfire]

The secret to the cypress’ fire resistance lies in its camel-like ability to store water, they researchers said.

Like the other trees that burned in the summer of 2012 blaze, the cypress had endured a brutal combination of the “three 30s” — temperatures over 30 degrees Celsius (86 degrees Fahrenheit), less than 30 percent humidity and wind speeds of over 30 kilometers (19 miles) per hour. The heat and wind scoured the rest of the forest dry, and the lack of humidity and rainfall meant there was no water to replenish it. By the time some spark ignited the forest fire, the plot was a dried-out box of tinder.

Except for the cypress. Of the hundreds of trees planted in the experimental plot, only 12 were burned. The plants in the interior of the patch remained un-scorched and brilliant green — the fire that raged across thousands of acres couldn’t pass through a few layers of cypress to reach them.

These narrow conifers benefited from thick, protected, scale-like leaves that are perfectly designed to retain water, the researchers told the BBC. The moister plants were more difficult to set ablaze. Experiments in a lab showed it can take as much as seven times as long for a Mediterranean cypress to ignite as it would take another tree.

Even the dead debris cast off by the cypress is less flammable than that of other species. While dead leaves and fallen needles are usually quick to ignite, the cypress “litter” forms a dense, sponge-like carpet on the forest floor, lead author Gianni Della Rocca, research technologist at Italy’s Institute for Sustainable Plant Protection, told the BBC. The cypress carpet did a better job retaining water and had fewer air pockets than other kinds of litter, helping to suffocate incipient fires.

Spain was struck by its worst drought in 150 years last summer, and much of the Mediterranean region has suffered recently from fires as devastating as the ones currently raging in the western United States. According to the BBC, citing statistics from the UN’s Food and Agriculture Organization, roughly five million acres of forest were burned between 2006 and 2010. This summer has been one of blistering temperatures, little rainfall and repeated wildfire evacuations in Spain and Portugal, just as it has in the American West.

That makes the possibility of a flame-resistant fire barrier deeply compelling in the sun-scorched, rain-deprived region. Already, buffer zones of cypress are being planted in Spain and Italy to see how they deter future blazes.

“In a few years, we will have cypress barriers and observations at real scale,” Della Rocca told the BBC.

If it works, the Mediterranean cypress could be put to work elsewhere as well — the mountains of Patagonia, perhaps, or the forests of California.

The cypress has “great plasticity in terms of soil, climate and altitude,” enthused Bernabe Moya, who works for the Monumental Trees Department in Valencia, Spain. “It can grow on all soils, even degraded ones, apart from those that are water-logged, and it thrives from sea level to altitudes of more than 2,000 meters [more than a mile high].”

[The forests of the world are in serious trouble, scientists report]

Other biologists were more skeptical. Speaking to El Pais in 2012, botanist and conservation expert Nicolás López warned that cypress may block fires, but it also blocks the growth of other plants and trees.

“Introducing a species that isn’t native is a mistake. It changes the ecosystem and endangers the rest of the flora,” he said. He acknowledged that the cypress could still be used to protect urban areas.

But Moya urged that something must be done. Forest fires are only becoming more frequent with climate change, he told the BBC. If we don’t find a way to manage and protect our trees, we’ll soon find ourselves without them.

“The fight against fires concerns us all,” he said. “We owe it to the forests and we owe it to future generations.”