In recent months, storms of earth, dust and sand have been recorded in at least four states across the country. Several cities in São Paulo, Minas Gerais, Mato Grosso do Sul and Maranhão were hit by this phenomenon known as haboob, Arabic word which in free translation means “destroyer that crawls”. The rains returned, and the storms ebbed. but they left deep scars. At least four deaths in São Paulo were attributed to the waves that darkened the sky in the affected areas: without visibility, three people were burned to death while trying to fight a fire in Santo Antônio do Arancaguá, and one died after strong winds knocked down a wall in Tupã. These storms, common in dry areas and in the Brazilian semiarid region, are related to the environmental devastation underway in the country, and also have the help of another harmful phenomenon, according to specialists: soil desertification.
Desertification is a process that makes it easier for storms and their strong winds to carry away sand and dust. It occurs when the natural protective layer of the soil, formed by organic matter, forests and forest, is removed, leaving the land exposed. “Without this layer, the soil is very dry, it loses its capacity to absorb water, it becomes brittle and dusty. This destroys its balance and consequently worsens our quality of life”, explains Tatiana Tucunduva P. Cortese, a researcher at the Institute of Advanced Studies at USP and professor of the Master’s Degree in Smart and Sustainable Cities at Uninove.
But what causes this imbalance in the soil? “Desertification occurs due to the inadequate use of soil, water and vegetation. It is often the result of predatory human action on ecosystems”. One of the factors responsible for the phenomenon is the intensive use of land for agricultural activities — which occurs in the western region of São Paulo, one of the main areas affected by sand storms and punished by drought. “These activities revolve the soil a lot. This practice, added to the use of fertilizers, pesticides, reduces the amount of organic matter that covers the soil and keeps it cohesive, leaving it vulnerable”.
With no vegetation cover or organic matter, the amount of loose dust and sand increases. “These sandstorms are caused by two factors: very strong wind and loose dust and earth, easily raised by the gusts”, explains Marcelo Seluchi, researcher and meteorologist at the National Center for Monitoring and Alerting of Natural Disasters (Cemaden). “And this year was another year of drought, with a lot of dust deposited on the ground”, he says. Thus, the lack of rain collaborates with desertification, and the perfect scenario for the proliferation of haboob by various regions of the country, mainly in the Southeast.
What happened this year, with dozens of haboob cutting across São Paulo and other states is not considered normal. “These sandstorms are infrequent [nessas regiões], I don’t remember having a year with so many. This is unusual,” says Seluchi. “I see a relationship between drought [que colabora com as tempestades de areia] and the alteration of the hydrological cycles caused by the deforestation of forests”, he says. According to the researcher, for decades the Southeast and Center-West regions have registered rates below the average of precipitation. “This is not a one-off fluctuation, it is a trend: a constant and systematic reduction in rainfall. And such a trend can only be explained by a cause that also persists over time. I only know two effects that have remained over the last few decades: one is deforestation, the change in land use, and the other is global warming, derived from the greenhouse effect”.
Cortese, a researcher at the IEA-USP, also points to the role of deforestation in worsening the environmental situation and in the proliferation of sand storms. “Deforestation makes this situation worse and is a warning: the humidity that native vegetation and forests bring regulates the rainfall regime in the Southeast. If the area without vegetation cover increases, there is an impact on the rains”, says the teacher. ”And this is not unique to the Amazon, it is also true for the Atlantic Forest, the Cerrado… Regarding the Amazon forest, we have something very evident, which are the flying rivers, which bring the water vapor transported by air currents. When we take out the forest, that large reservoir will run out, and there will certainly be less water circulating”. And drier. And more sandstorms.
With the arrival of the rains in late October, the number of haboob in the Southeast region it decreased. That’s because the water helps to fix dust and sand to the ground, preventing the gusts of wind from carrying the particulate matter to cities. But what happened this year is a warning, according to specialists, of what could become the new climate normal in Brazil, as a result of the climate emergency: drought and desertification, rain concentrated in a short period of time and sand storms in the cities. “These phenomena will all increase in frequency and intensity. That’s why we need to act,” says Cortese.
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