Can a Place with Heavy Rainfall Be Called a Desert? The Mystery of Lençóis Maranhenses

The Lençóis Maranhenses National Park lies in northeastern Brazil and is famous for its white sand dunes and lakes of fresh water. In the rainy season, rainwater pools in basins formed in the ever-changing sands to form thousands of temporary lagoons, which dry out as the dry season advances. Though it looks like a desert, this national park is not technically a desert since it gets abundant rains during some seasons. It was included in the UNESCO World Heritage list in 2024.

Where Is Lençóis Maranhenses National Park Found?

Lençóis Maranhenses National Park can be found in Maranhão state on the northeastern coast of Brazil in South America. The national park is located within the Barreirinhas basin, where there are extensive stretches of white sand dunes and lagoons.

Lençóis Maranhenses National Park has an area of about 156,562 hectares, which is equivalent to about 1,566 km². There are about 90,000 hectares of dune fields in the national park, while about 40,000 hectares have restinga vegetation.

There are about 80 kilometers of coastal land in the park. This national park is renowned internationally due to its spectacular natural scenery and dune formation, which occurred thousands of years ago.

Why Is the Park Desert-Like but Has Freshwater Lagoons?

Lençóis Maranhenses looks like a desert because of the presence of vast white sand dunes. However, this park does not belong to the class of deserts since it is characterized by a semi-humid climate with a wet season.

The rainfall received during the wet season fills up the hollows between the dunes, resulting in lagoons with diverse shapes, sizes, depths, and colors. The lagoons are supplied by rainwater only, with no traditional sources or drains.

As the dry season advances, many temporary lagoons dry out due to the process of evaporation or fluctuation in the groundwater level. The lagoons resurface in new locations and different shapes in the next wet season.

This natural phenomenon highlights the link between climate, hydrology, and topography of the park.

Formation of the Sand Dunes

The formation of Lençóis Maranhenses has been a result of sedimentation and the action of wind in the Quaternary period that started about 2.58 million years ago.

Coastal sediments are deposited by the marine forces, and winds act upon them, forming dunes. Winds that blow in one direction cause the formation of crescent-shaped dunes referred to as barchans.

The dunes are formed in long chains stretching inland. As indicated by UNESCO, a dune chain can be as long as 75 kilometers, and some of the dunes grow up to 30 meters tall.

Dune mobility is another unique aspect. As indicated by UNESCO, the speed of dune migration is up to 4 to 25 meters per year. This indicates that the landscape keeps changing as a result of the wind and other forces of nature.

The interaction between mobile dunes, seasonal lagoons and coastal sediments creates a unique natural environment for geomorphology studies.

UNESCO World Heritage Site: Why Does It Matter?

Lençóis Maranhenses National Park was included in the UNESCO World Heritage List in 2024 due to its outstanding natural value.

The park received World Heritage status due to two criteria for natural heritage:

• Criterion (vii): Natural beauty – Lençóis Maranhenses National Park features an exceptionally beautiful landscape that includes huge white sand dunes with freshwater lakes.
• Criterion (viii): Geological value – Lençóis Maranhenses National Park exhibits important geological processes in the formation of coastal formations in the Quaternary period.

This site is especially important due to the widespread development of dynamic coastal dunes and freshwater lakes.

It shows the global significance of the park and emphasizes the need for its conservation and management.

Park Protection and Management

Lençóis Maranhenses National Park was founded in 1981 and is managed by the Chico Mendes Institute for Biodiversity Conservation (ICMBio). ICMBio is the federal institution responsible for Brazil’s protected areas.

It constitutes a protected area within the National System of Conservation Units in Brazil. The park is classified as integral protection unit where natural resources are subject to conservation regulations and exploitation is prohibited.

A buffer zone of about 268,231 hectares provides a further level of protection for the natural ecosystems found within the national park.

The management focuses on biodiversity conservation, environmental pressures, regulation of tourism activities, and involving local/ traditional communities in decision-making processes. This is essential since increasing tourism can have an impact on the fragile ecosystems of the dunes and lagoons.