Brazil does not contain any true deserts based on standard climatological definitions. The country is overwhelmingly dominated by humid and tropical climate systems, which prevent the formation of large, permanently arid zones. While true deserts are absent, Brazil does contain extensive semi-arid regions and unique landscapes featuring large sand dunes. These features often lead to public confusion about its overall climate.
What Defines a True Desert
A true desert is defined primarily by its aridity, which is a measure of the long-term lack of effective moisture. The simplest, widely accepted standard for an arid region is receiving less than 250 millimeters (about 10 inches) of precipitation annually. Aridity is more precisely quantified using an aridity index, which compares annual precipitation to potential evapotranspiration (the maximum water loss possible). For a region to be classified as arid, the water loss must vastly exceed the water gain. Semi-arid regions, in contrast, receive slightly more moisture, typically between 250 and 500 millimeters of rain per year, allowing for more sparse vegetation.
Brazil’s Predominant Climate Systems
Brazil avoids desert formation due to its geographic position and atmospheric circulation patterns that ensure high moisture levels. The country is dominated by Tropical, Equatorial, and Subtropical climate types, characterized by high temperatures and significant rainfall. The Amazon Basin acts as a major moisture source, with its rainforest contributing vast amounts of water vapor through evapotranspiration. This moisture is carried across the continent by atmospheric circulation.
The proximity of the Atlantic Ocean is also a factor, as warm, moisture-laden trade winds constantly sweep inland. Furthermore, the constant movement of the Intertropical Convergence Zone (ITCZ), a band of low pressure near the equator, brings intense rainfall to the northern and central parts of the country. These factors create a predominantly humid environment, preventing the sustained dryness needed for true desertification.
The Semi-Arid Northeast Sertão
The region most commonly mistaken for a desert is the Sertão, the vast interior of the Northeast. This area has a hot, semi-arid climate and is home to the Caatinga biome, a unique tropical xeric shrubland. The Caatinga, meaning “white forest,” consists of drought-resistant scrub and small trees that shed their leaves during the dry season. While the landscape can appear barren, the Sertão is classified as semi-arid steppe, not a desert.
Annual rainfall typically ranges between 500 and 800 millimeters, well above the 250-millimeter desert threshold. Rainfall is highly irregular and concentrated in a short, intense wet season, contributing to severe drought cycles known as secas. These periods of unpredictable drought cause significant environmental and economic hardship.
The Sertão’s dryness is caused by the Intertropical Convergence Zone remaining north of the region for much of the year due to the relatively cool temperatures of the South Atlantic Ocean. Recent studies indicate that a small area in the northern part of Bahia state (about 5,700 square kilometers) has transitioned from semi-arid to arid conditions. This localized change represents Brazil’s first officially recognized arid zone, though the rest of the Sertão remains semi-arid.
Landscapes Often Mistaken for Deserts
The visual appearance of certain Brazilian landscapes often leads to the misconception that the country harbors deserts. The most prominent example is the Lençóis Maranhenses National Park, located in Maranhão state. The park features vast fields of brilliant white, sweeping sand dunes that can reach heights of up to 40 meters. These dunes were formed by coastal sediments carried inland by wind.
Despite the sandy terrain, the region is not a desert because it receives substantial annual rainfall, sometimes exceeding 1,200 millimeters. During the rainy season, this water collects in the valleys between the dunes, forming thousands of temporary freshwater lagoons. The presence of these seasonal lagoons, prevented from draining by an impermeable rock layer, fundamentally distinguishes the area from a true desert.