It is 42 degrees Celsius, there has not been any rain for weeks, and the risk of a wildfire is severe. In this dusty corner of southeastern Spain in August, the grass has turned yellow, and fields of cereals are perishing in the heat after months without rain. Walking along the road, it feels as if your skin is burning in the heat.
But on the outskirts of Ribarroja, a small town near Valencia, there is an unusual line of defense against a possible blaze. Looming above the trees near the edge of the town is a series of huge green towers that resemble streetlights. They act as mammoth water sprinklers, showering the trees and bamboo plants below with recycled water to reduce the chance of fire. They’re supplied with recycled water from the nearby houses in Ribarroja and neighboring Paterna.
This is the biggest defense system against wildfires in Europe, consisting of 40 towers that encircle the towns, the largest standing 24 meters tall. Known as the Guardian project, it protects urban areas surrounded by trees or other vegetation from the devastating effects of a wildfire by hydrating the plant life, creating a natural barrier. With climate change increasing the threat of wildfires across the continent, Guardian-style defenses could become a fixture of high-risk parts of Europe in the future.
Watering vegetation can delay the spread of a blaze because plants containing greater amounts of moisture require more of a wildfire’s energy. Other factors affect the spread of a wildfire—wind speed is crucial, for example—but generally the drier the vegetation, the more quickly a fire will consume the landscape.
“Water eats up some of the energy of a fire,” says Ferrán Dalmau, CEO of forest fire consultancy Medi XXI GSA, which developed the Guardian system. “If a plant is better hydrated, then it will slow down the fire.” But Dalmau warns that the system will not put a fire out. Guardian can slow and help control a blaze, but it doesn’t replace the need for fire services to intervene.
Indeed, hidden among the undergrowth is Guardian’s second line of defense: a series of sensors. These pass information to local fire authorities in real time, 24/7, about the humidity levels of the plants and the resulting fire risk. Based on this information, fire services are put on a higher level of alert if the risk rises. Citizens can also be sent updates on the fire risk via the messaging service Telegram.
Having shown me the Guardian system in situ, Dalmau then takes me to his office and shows me how, thanks to these sensors, the system can indicate areas that could be affected by a fire, as well as simulating how the fire might evolve. Dalmau shows me a computer graphic of the area we have just walked through. The irrigated area is a brown color, which means it is safer, but around it the rest is bright red—meaning it would be at maximum risk from a blaze. An algorithm calculates the fire risks.
After a prolonged drought and searing temperatures, 2022 has been the worst year ever for forest fires in Spain. So far this year, 275,000 hectares—roughly four times the area of New York City—have burned, which is more than quadruple the country’s annual average, according to the European Forest Fire Information System. Tens of thousands of people have been forced to evacuate their homes as blazes have raged.
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Here in Ribarroja, Guardian has yet to face down an intense summer blaze. But this isn’t the first place where the system has been installed. It started as a pilot project in 2006 in Carcaixent, another town near Valencia, and 10 years later it was put to the test when a blaze threatened to destroy the town.
“Those events are engraved on my mind with a lot of bad memories and a lot of bonuses,” says Enrique Lencina, who was president of the Carcaixent residents’ association at the time of the fire. Plumes of water poured out over the trees surrounding the settlement, stopping the blaze in its tracks and proving that the solution works. Dramatic photographs show how the fire halted just before a line of homes and trees damped by this earlier version of Guardian, which used drinking water rather than recycled water. “I can say that the system saved our houses from being destroyed,” says Lencina.
Aware of the system’s success in Carcaixent, and faced with a high risk of forest fires in this arid corner of Spain, authorities in Ribarroja and Paterna—two towns with a combined population of about 90,000—then hired Medi XXI GSA to develop a system to protect their residents. Urban Innovative Actions, an initiative of the European Union that seeks to find sustainable solutions to urban problems, backed the project with a €4.4 million (about $4.38 million) grant, which supplied 80 percent of the funding. The newer system using recycled water was created in 2019.
The new version of Guardian uses just over 70 million liters of water per year to defend the towns—about 28 Olympic swimming pools’ worth, a fraction of the total processed at the local water-recycling plant. Health authorities must give permission for the recycled water to be used. Before it is pumped out into the system, it undergoes a series of tests to eradicate any possibility of bacteria entering the system, with authorities checking the results.
“The greatest value [of Guardian] is that it can use reclaimed water,” says Dalmau. This, he explains, is treated using ozonation and activated carbon filters before being sprinkled from the towers at regular intervals each day. For the Ribarroja and Paterna councils combined, it costs about €100,000 per year to run the system—just over €10 per inhabitant each year. It’s a kind of insurance against a house fire, with the cost absorbed by the local authorities.
As forest fires have destroyed hundreds of thousands of hectares of land in the US, Europe, and elsewhere, interest in the Guardian system has boomed. Dalmau says he has fielded calls from authorities in Valencia, Barcelona, and Malaga in Spain, as well as further afield in Italy, California in the US, and Valparaiso in Chile. A portable version of the system is also being used by the Spanish army’s Emergency Military Unit, which tackles fires across the country, while Spanish forest engineers are using it to train local civil protection units to defend strategic areas.
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But it can’t be used everywhere. “The system is suited to urban areas which are bordered by vegetation or woods,” says Dalmau. “It would not work in rural forests or agricultural areas, where fires can only be controlled by forestry methods. Those areas would require forestry measures to prevent fires spreading.” These include reducing the amount of vegetation in woods and carrying out controlled fires in winter, explains Elsa Pastor, an expert in forest fires at the Polytechnic of Catalonia who supervised the Guardian project in Valencia for the European Union.
A further limiting factor is that communities must have the ability to recycle water to use Guardian, explains Pastor. Then there’s the expense of installing and running the system—though communities “must weigh up the costs of the risks of not doing anything about fire risks and the costs of installing the system,” she says.
And the costs of inaction could be high. An unpublished study from the University of Valencia suggests that the cost of not implementing a fire-protection system like Guardian could be €31 million for Ribarroja and Paterna, should a wildfire hit the area. Francesc Hernández, a professor of water economics at the university, based the calculation on the likely bill for damages if a forest fire destroyed the nearby towns and forests, together with the costs of putting it out.
Europe’s wildfire season this summer reflects the shape of things to come. Land temperatures across the continent are projected to increase by at least another 1.2 to 3.4 degrees Celsius by the last few decades of this century, and Europe is also currently warming faster than other global hotspots. With this rising heat comes an increased risk of wildfires, and alongside it, a need for better ways to control blazes.
“In the face of climate change and extreme wildfires, we can be part of the problem or part of the solution,” says Dalmau. “Guardian is undoubtedly a relevant contribution to the solution.”