This massive sprinkler system can protect cities from wildfires.

It is 42 degrees Celsius, no rain for weeks, and wildfire danger is severe. In August in this dusty corner of southeastern Spain, the grass has turned yellow, and the cereal fields are dying of heat after no rain. Walking on the street, your skin feels like it’s burning in the heat.

But there is an unusual fire line on the outskirts of Ribaroja, a small town near Valencia. Looming above the trees near the edge of town are a series of giant green towers that resemble streetlights. To reduce the risk of fire, they work like mammoth water sprinklers, washing the trees and bamboo plants below with recycled water. Recycled water is supplied from houses in Ribaroja and neighboring Paterna.

This is the largest fire prevention system in Europe and has the largest towers 24 meters high, surrounding 40 cities. Known as The Guardian Project, it protects urban areas surrounded by trees or other vegetation from the devastating effects of wildfires by watering them with plant life and creating a natural barrier. As climate change increases the threat of wildfires across the continent, Guardian-style defenses could be the future of high-risk parts of Europe.

Watering plants can slow the spread of fire because plants with high moisture content require more wildfire. Other factors influence the spread of wildfires—wind speed is important, for example—but in general, fires consume the landscape more quickly when vegetation dries out.

“Water consumes some of the fire’s energy,” says Ferran Dalmau, CEO of forest fire consultancy Med XXI GSA, which developed the Guardian system. “If a plant is better hydrated, it will reduce the fire.” But Dalmau cautions that the system won’t put out fires. The guard helps to slow down and control the fire, but does not replace the need for fire services to intervene.

Indeed, hidden among the lower developments is the guard’s second line of defense: a series of sensors. These transmit real-time, 24/7, information about vegetation moisture levels and resulting fire risk to local fire officials. Based on this information, the fire services will be on high alert if the accident occurs. Citizens can send updated information about fire by telegram.

Dalmau took me to his office to show me the guard system in place and how, thanks to these sensors, the system can indicate areas that may be affected by fire and how the fire changes. Dalmau showed me a computer graphic of the area we had just passed. The irrigation area is brown, which means it is safer, but the rest around it is bright red – which means there is a high risk of fire. The algorithm calculates fire risks.

After a long drought and high temperatures, 2022 is the worst year ever for forest fires in Spain. So far this year, 275,000 hectares – nearly four times the size of New York City – have burned, more than four times the national annual average, according to the European Forest Fire Information System. Tens of thousands of people have been forced to leave their homes because of the fires.