In the last forty years, the Canary Islands have suffered the consequences of 28 large forest fires (GIF), that is, burning in which the calcined surface exceeds or reaches 500 hectares, with a clear atmospheric pattern behind most of them: intrusions of Saharian dust (calima) and low altitude thermal investment.
Researchers from the University of La Laguna (ULL) have published a Scientific study In the academic magazine Geographies detailing the environmental conditions before and during these episodes of uncontrolled fires, whose risk of producing will increase Because of the climate crisis caused For human beings.
The results of the publication show that these fires, which have burned a total of 132,000 hectares in the archipelago, almost 18% of their territory and practically its entire forest area, have a “very close” relationship with thermal investment, an atmospheric layer characteristic of the Canary Islands that makes the temperature increase instead of descending as it is earned in altitude.
The ‘invisible ceiling’ that announces that drastic change of temperatures is the particular sea of clouds that the mountainous islands of the autonomous community present and maintains the humid air down and dry, above. It is a unique stamp in the Canary Islands with more background than it seems in the first instance.
The authors have shown that, at the beginning of most of these fires, the base of the thermal investment was located at an average altitude of 369 meters high, a figure “well below” the general average registered between 1983 and 2023, located at 1,010 meters, and even below the average recorded in summer (792 meters).
This has important implications. When the thermal investment base drops below 400 meters, almost the entire forest mass of the archipelago (96.7%) is above it. The forests lose their usual freshness and humidity of the winds (always below the aforementioned sea of clouds) and are exposed to a layer of warm and very dry air, so the chances of extending the flames increase considerably.
In it 2019 fire that burned more than 10,000 hectares in Gran Canariafor example, thermal investment on the start of fire was about 205 meters altitude, within 3.5% of the lowest levels of the entire historical series. In the 2023 Tenerife, it was 287 meters.
For more Inri, the same researchers who have signed this study, Jordan Correa and Pedro Dorta, members of the ULL disaster risk reduction chair, published Another academic jobOr a few months ago they found that the altitude of the Sea of Clouds of the Canary Islands had descended a hundred meters of average since 1970, unprotected the laurisilva and the pine forest.
“The lower the thermal investment, there will be a greater forest extension in a layer of dry and warm air and, therefore, the greater risk of forest fires,” summarizes Dorta.
Both experts used data from the European Center for Middle Term weather forecasts (ECMWF), which collects temperature figures from layers near the surface to an eighty kilometers of altitude. And they also used climatic series of the meteorological stations closest to large fires to calculate interest variables such as maximum temperature, relative humidity, precipitation and wind intensity.
The investigation also recalls that the summer reduction of thermal investment in the archipelago “coincides” with the arrival of Calima. And the calima, as such, further aggravates the arid conditions of the land, raising temperatures often above 35 degrees, causing a “extremely low” relative humidity and generating winds with gusts of up to 60-70 kilometers per hour. An explosive cocktail for large fires.
“The vast majority of the hectares that burn in the Canary Islands when an advection of Saharan airs that involve a radical modification of environmental conditions,” explains Dorta. The geographer adds that the islands can go from having “soft” temperatures and a relative “high” humidity, to register an increase of up to 20 degrees in the first variable and a decrease in sixty points in the second when the desert dust makes an appearance.
Dorta warns that, in that case, the environmental conditions are “so extremely” dry and warm, that if forest fires are not controlled at the beginning, when they continue to be conatos (less than one hundred hectares affected), “Extinction is practically impossible”. “It is only going out when time changes or all the fuel has been burned,” he laments.
The conclusions of the study show, in fact, that 95% of the burned surface in the islands corresponds to large forest fires. And the authors consider that the archipelago is the Spanish region with the greatest risk that small flames become gif precisely because of that: although this is autonomy with the lowest percentage of forest area over the total (just 18%), and there are less fires than in the rest of Spain, when the mountain burns, it usually makes it large.
“We have a lower number of claims, a smaller number in general fires. But when we have them, they are usually very large. And when they occur, they affect great surfaces and are very difficult to manage. In other Spanish areas they can have many more fires, but they do not become as frequently in GIF as in the Canary Islands,” Correa reflects.
Other results of the publication suggest that most of the great forest fires in the archipelago occurred in the months of August (11) and July (9); that the most affected islands have been Tenerife (48,000 hectares), Gran Canaria (31,100 hectares) and La Palma (23,600 hectares); And that there has not been a “significant” increase in them in recent decades, but those who have damaged the Canarian field do it more and more virulence.
“Climate change is not making more fires in the Canary Islands, but we can say that those that occur tend to affect more surface and are more difficult and complex [de atajar]”, Adds Correa.
The average maximum temperature on the start days of these large bones was 30.3 degrees, with thermal anomalies that exceed ten degrees. The minimum relative humidity in those same days is usually 24.3% (in some extreme cases below 10%). And in half of the episodes the direction of the wind was northeast. However, when the gusts came from the East, the fires affected many more hectares, since these winds are usually associated with Saharian air intrusions.
More findings have to do with precipitation. The study did not find a relevant correlation between dry or humid years and large forest fires. The rains in the archipelago usually occur outside the time of greatest risk of burning. The field is already dry to summer, so the mountain “It remains with a accused water deficit” for a long timeindicates Dorta. “Aridity is a structural characteristic of the Canarian environment,” he rises.
That is another cause. As well as thermal and calm investment. But so are the abandonment of agriculture or negligence that cause intentional fires, in Dorta’s opinion.
For him and for Correa, it is crucial that the Canary Islands begin to monitor in real time the altitude of thermal investment and a key element to prevent fires, which bet on a detailed and localized analysis of the weather (by the microclimates of the islands) and that continues with the firewallearly detection systems, public awareness programs and land planning that avoids building in high -risk areas.
“Future fire management strategies must incorporate adaptive planning to the climate that anticipates more long fires, more frequent heat waves and a greater number of days with own weather conditions for fires. Only through a comprehensive and prospective approach can mitigate the impacts of large forest fires in the Canary Islands,” concludes the investigation.
