Volcanic CO2 threatens these villagers. High-tech sensors are keeping them safe.
| Puerto Naos, Spain
A gentle breeze sends waves lapping onto the sand as a smattering of sunbathers spreads lazily out on beach towels; a pair of children splash in the water.
A typical tourist scene in the Canary Islands. But it is possible only because of an unprecedented network of monitors, testing the air for poisonous levels of carbon dioxide.
For two years, the black sand beach here was deserted, its ice cream stands and souvenir shops shuttered with signs reading 鈥�Peligro!鈥� (鈥淒anger!鈥�). Only now are tourists starting to return to Puerto Naos, this slice of paradise in La Palma.
Why We Wrote This
A story focused onLava wasn鈥檛 the only hazard from the 2021 Cumbre Vieja eruption in La Palma, Spain. Concentrations of carbon dioxide spiked as well, threatening locals鈥� health. But an innovative network of CO2 detectors is helping keep them safe today.
In September 2021, the Cumbre Vieja volcano erupted a few miles away, spewing lava down the hillside toward Puerto Naos and the nearby fishing village of La Bombilla and forcing the evacuation of over 1,000 people.
Months later, scientists discovered something far more insidious: The volcano had caused an unexpected seismic reaction that released hazardous levels of CO2 鈥� once trapped in the ground 鈥� into the air. During the evacuation period, some areas in town had reached air concentrations of CO2 as high as 480,000 parts per million 鈥� over 400 times the acceptable limit.
鈥淭here were dead birds and cats on the ground close to garages and basements,鈥� says Nemesio Per茅z, scientific coordinator at Involcan, a geological institute in Tenerife. 鈥淭hat鈥檚 when we realized we had a problem.鈥�
Before long, Mr. Per茅z joined a working group of Spanish authorities and other geological experts. In 2022, they launched Alerta CO2, a 鈧�4 million ($4.5 million) project funded by Spain鈥檚 national government, and the first of its kind globally to monitor gas levels on a large scale.
Now, there are more than 1,300 CO2 detectors in Puerto Naos and La Bombilla, making the villages the most monitored in the world for the gas.
The project has not only allowed around 80% of homeowners to return, but could also provide lessons for other communities facing environmental disaster going forward.
鈥淲e鈥檙e constantly monitoring the air quality here,鈥� says Javier Llamas, the mayor of Los Llanos de Aridane, the town most affected by the volcanic eruption. 鈥淧eople shouldn鈥檛 have to worry about the basic necessity of breathing clean air.鈥�
On watch for CO2
Jutting out from a rocky cliff is the majestic Meli谩 La Palma, Puerto Naos鈥� only hotel and the area鈥檚 biggest draw. After the volcano erupted and the town was evacuated, there were questions about whether the hotel would get back on its feet. Three years later, it is at full capacity.
鈥淢any guests write us to ask if there is still gas in the area, if businesses are open, and if it鈥檚 safe,鈥� says Irving Ribot, manager of Meli谩 La Palma. 鈥淲e just try to reassure them that when they鈥檙e in the hotel, they鈥檙e monitored all the time.鈥�
There are 55 CO2 detectors spread throughout the hotel, discreetly placed in hallways, inside the restaurants, and in the lounge area. Most guests will never even notice the grapefruit-sized detectors. But if concentration levels get too high, an alert goes off in the offices of Alerta CO2 just up the road.
There, Mr. Per茅z and his team have set up a makeshift office in an elementary school left empty after the COVID-19 pandemic.
鈥淲e鈥檙e here 24 hours a day, seven days a week,鈥� says Marisol Gonzalez, project coordinator of Alerta CO2, as she pulls up a spreadsheet worthy of a sci-fi film. On her computer screen is data from each of the homes in Puerto Naos and La Bombilla using their detectors.
Normal levels should be below 770 ppm. If the CO2 concentrations go above 1,000 ppm continuously for 30 minutes, firefighters in the office next door make a call to the home or business. Those who need help get a personal visit; otherwise, they鈥檙e encouraged to go outside and air out the space.
That can mean simply opening the windows or, in some buildings, using the air purifiers that the Alerta CO2 team devised 鈥� imposing machines that introduce clean air in and flush bad air out. Some residents have complained that the machines are ugly or noisy. But, asks Mr. Per茅z, 鈥淲hat do you want, gas or noise?鈥�
Homecoming for Puerto Naos locals
There鈥檚 no way of knowing how long it will take for the ground to stop releasing CO2 because, says Mr. Per茅z, there are no scientific tools to forecast the end of the problem. But levels consistently went down in the last half of 2024, which has allowed people to return to their homes and businesses.
The first 139 people returned in December 2023, and returnees have progressively increased since then. Over 900 homes and businesses in Puerto Naos and La Bombilla have now been authorized to reopen.
That鈥檚 reassuring for Margaret Per茅z, who spent her entire adult life in Puerto Naos and raised her children here. When the town was evacuated, she went to live with family in nearby Los Llanos. But she always had her eye on returning.
鈥淪ome people are scared of coming back, or they ended up in a bigger town and decided they liked it better there,鈥� says Ms. Per茅z, who works at the only grocery store in the village. 鈥淣ot me. I love it here.鈥�
There are still zones closed off around Puerto Naos and La Bombilla, and several underground parking lots and basements remain sectioned off with sticker tape and 鈥淒anger!鈥� signs. Along the boardwalk, a rhythmic, green light flashes on the outdoor CO2 detectors 鈥� a constant reminder that the area is not out of the woods yet.
The La Palma regional government has since created the app, where people can see outdoor CO2 levels in real time. Local business owners are doing their best to reassure clients.
鈥淥ne girl came in and saw the CO2 detector and said, 鈥榃hoa, it鈥檚 at 800 ppm in here!鈥� She was nervous,鈥� says Maria Malik, a local hairdresser. 鈥淏ut in reality, if you have any enclosed room full of people, your CO2 levels are going to go up from simply breathing.鈥�
