It Looks Like a Desert. But It Has Thousands of Lakes

Key Concepts

• Lençóis Maranhenses: A unique national park in northeastern Brazil characterized by vast fields of white sand dunes interspersed with seasonal freshwater lagoons.
• Biome Intersection: The location where three distinct biomes meet, contributing to high biodiversity.
• Dune Migration: The constant movement of sand dunes, which can shift up to 80 feet annually.
• Seasonal Lagoons: Thousands of freshwater lagoons that form between the dunes during the rainy season and evaporate during the dry season.
• Underlying Rock Layer: A geological feature that traps water beneath the dunes, preventing it from sinking completely.
• Endemic Species: Species found only in a specific geographic area, such as the Pininga turtle in Lençóis Maranhenses.
• Adaptation to Dryness: Survival strategies of local fauna, like turtles hibernating and fish eggs being resistant to drought.
• "The Desert That Breathes": A nickname for Lençóis Maranhenses due to the dynamic movement of its dunes.
• Climatic Emergency Relevance: The potential for studying Lençóis Maranhenses to yield insights applicable to climate change challenges.

Lençóis Maranhenses: A Surreal Landscape

Lençóis Maranhenses, located on the northeast coast of Brazil, is described as a place that evokes a sense of being on another planet. Despite its appearance as a desert, it receives significant rainfall, approximately 1600 millimeters (63 inches) annually, which is more than that of Scotland or London. This high rainfall, combined with its unique geological and ecological features, distinguishes it from a true desert.

The park is situated at the intersection of three biomes, a rare occurrence that significantly boosts its biodiversity. It encompasses a vast field of dunes spanning 350 square miles. These dunes are not static; they migrate inland by up to 80 feet each year. During the rainy season, thousands of lagoons emerge between these shifting sand mountains, many of which are large enough for swimming. The dynamic nature of the landscape means that no two visits to Lençóis Maranhenses are ever the same, as the constant movement of sand and water reshapes the dunes and lagoons.

The Formation and Dynamics of the Lagoons

The formation of the lagoons is a key phenomenon in Lençóis Maranhenses. During the rainy season, the water level rises, filling the depressions between the dunes. A crucial factor preventing the water from simply sinking into the sand is an underlying rock layer. This impermeable layer acts like a bathtub, trapping the water and allowing the lagoons to form and persist.

The process can be visualized as follows:

1. Rainfall: Water accumulates in the depressions between dunes.
2. Lagoon Formation: The water level rises, creating visible lagoons.
3. Dry Season: As the dry season progresses, the water evaporates, and the water level recedes.
4. Underlying Water: Despite the visible evaporation, water remains trapped by the rock layer beneath the sand.

The dynamic nature of the dunes means that lagoons are transient. A lagoon that exists in one location one year may be buried by migrating dunes the next, with new lagoons forming further ahead. This constant reshaping is driven by strong winds that primarily blow from a single direction.

Sand Dynamics and Wind Influence

The sand in Lençóis Maranhenses is characterized by its fine grain size and loose texture, allowing it to flow down dune slopes like water. Strong winds, predominantly from a consistent direction, are the primary force behind the dune migration. These winds lift the dry, fine sand and transport it inland, building new dune ridges.

The constant wind activity means that traditional navigation methods, such as maps, are often ineffective. Locals, who have lived in the area for generations, rely on their understanding of wind patterns and ridgelines for navigation. The wind can dramatically alter the landscape within a single day, flattening dunes or creating new ones. This constant reshaping, where everything is "destroyed and rebuilt every single year," has earned Lençóis Maranhenses the nickname "the desert that breathes." The wind also erases tracks, making it easy to get lost if one deviates from familiar paths.

Biodiversity and Endemic Species

Lençóis Maranhenses is a hotspot for biodiversity due to the intersection of three biomes. The park is home to unique flora and fauna, some of which are endemic to the region.

• Pininga Turtle (Water Tiger Turtle): This is an endemic species that plays a significant role in the park's conservation efforts. The Pininga turtle survives the dry season by digging burrows beneath the dunes, entering a state of reduced metabolism to conserve energy until the next rainy season.
• Fish: Many fish species in the lagoons have life cycles shorter than one year. They reproduce by laying eggs that are highly resistant to dryness. When the rains return, these eggs hatch, and life is revitalized.
• Salt Marshes: Unusually, salt marshes are found far from the ocean in this region, a deviation from the norm where they typically occur close to the coast due to their need for salt.

The park's unique environment presents challenges for its inhabitants. For communities living near the dunes, the constant migration of sand can necessitate relocation. As dunes encroach on their homes, families may have to move every few years. During the dry season, to prevent fish from dying from drought, locals will move fish from drying lagoons to those with more water.

Personal Reflections and Broader Implications

The experience of Lençóis Maranhenses is profoundly impactful, often described as life-changing. For a biologist who spent a year camping and surveying amphibians and reptiles, the opportunity "changed my view of life and helped to forge the biologist that I am today." Visitors often report a feeling of awe and a sense of profound peace, with some stating, "for the first time I’m breathing."

The park is considered a "micro-laboratory" with potential relevance to global challenges. Studying its unique ecosystem and the adaptations of its inhabitants could offer valuable insights for addressing the "climactic emergency."

The deep connection to the land is evident in personal sentiments, such as the desire to have one's ashes scattered across the lakes and moved by the wind and water, to "be part of it, forever." This reflects the powerful and transformative nature of this extraordinary environment.