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The recent California fires burned some 30 people and burned hundreds of square kilometers of land, destroying buildings and woods. At this time of year, fires in California are a fairly common occurrence, but their frequency and intensity have increased in part due to climate change and human activities. the New York Times has brought together the four main causes that lead to fires of this size, sometimes very difficult to control, and dramatic consequences.
climate
In principle, a fire needs some simple ingredients to develop: enough dry matter and a spark, which will lead to the development of flames. In California, most of the soil moisture accumulates in late fall and winter and gradually evaporates during the hot season. The vegetation becomes dry during the summer – usually little rain – with high temperatures and many hours of sun exposure. And it is precisely the dry vegetation that favors big fires.
The Californian climate is therefore still subject to these phenomena, but the data collected over the past decades indicate that the situation is worsening and that the main suspect is climate change, induced by human activities. The average temperature in many areas of the west coast of the United States has increased and as a result, periods of extreme drought have increased.
Fire smoke near Pulga, Northern California, November 11, 2018 (AP Photo / Noah Berger)
Nine of the ten largest fires since 1932, when they began keeping reliable records, have developed over the past 18 years. Five of them have been held since 2010 and only two this year. In a sense, the recipe for big fires has existed for centuries, but climate change is now helping to perfect it.
people
The cause of a fire like that of California may be the insignificant fall of lightning, but in many cases the responsibility is human. In addition to malicious cases, such as the activity of arsonists, many incidents can trigger flames. Last year, one of the biggest fires was caused by the fall of some power lines. The Carr fire, which has developed this year and is currently one of the six largest fires in the history of California, was caused by sparks caused by a truck shortly after the accident. Explosion of one of its highway tires.
Malibu House Burned by Woolsey Fire on November 11, 2018 (AP Photo / Jae C. Hong)
In times of drought, the risk of fire is very high and the human activities contribute to increase it considerably. In recent decades, the concentration of new homes near forests and forests has increased, inevitably leading to increased risks. In neighboring Nevada, for example, it is much more rare to build houses near areas most exposed to fire.
Fire Management
For many years, the way fires were managed has made matters worse. It was thought that the best strategy was to close them as soon as possible, preventing them from becoming too big. In fact, fires are a natural process that contributes to the regeneration of forests. The flames destroy some of the vegetation, remove the residues (leaves and dry branches) fallen to the ground and make the soil fertile for the rest of the vegetation. If you intervene to extinguish them suddenly, you stop this process by leaving a large accumulation of dry materials on the ground, which in the future will lead to even larger and more lasting fires.
From the point of view of our @NASAEarth satellites in the space, the fast #CampFire threatening several cities in California can be seen in natural color. Take a closer look at this image of #CaliforniaFires: https://t.co/ywQk1Lzo0K pic.twitter.com/0U5nLwqhrJ
– NASA (@NASA) November 9, 2018
The strategy currently followed by firefighters is therefore dedicated to controlling the perimeter of fires, so that they spread in less risky directions for the population, while waiting for its natural extinction. It is a very complex job that requires an excellent knowledge of the territory, weather conditions and is carried out using continuous aerial and satellite surveys of the state of a fire.
Twenty
The winds of Santa Ana, which blow very hard in the fall and bring dry air from the hinterland to the coast, are another ingredient in the recipe leading to the big Californian fires. Recent studies have shown that there are essentially two fire seasons: the first from June to September is the result of a combination of a drier and warmer climate, which is developing in western California, generally inland and at higher altitudes.
A second season is active from October to April and is powered by the winds of Santa Ana. Driven by strong gusts of wind, these fires spread up to three times faster than others, increasing the risk of reaching homes and residential areas, where they carry ashes and fragments still in fire. If October rains do not arrive or begin to fall several days late, as was the case this year, the winds can help further reduce the moisture and dry areas already affected. by a great drought. In similar conditions, just a few sparks to start a fire, which quickly becomes huge.
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