A Landmark on the Move
Morro do Careca, or "Bald Hill," is a 120-meter-high sand dune that defines the southern end of Ponta Negra beach in Natal, Brazil. The dune is not static. The dune is an active geomorphological feature, a mobile landform shaped by persistent aeolian processes. Prevailing winds from the southeast, with an average speed of 5.5 m/s, continuously transport sand from the coast, causing the entire dune to migrate inland. This movement is a slow-motion confrontation with the urban grid of Natal.
The dune is a visible component of the Barreiras Formation, a geological group of Cenozoic origin. The sand itself is primarily composed of fine quartz grains, with a median diameter of 0.10 mm near the dune. For centuries, this massive sand body was in a state of dynamic equilibrium, with sand supply from the coast balancing the material lost to wind transport. Increasing urbanization since the 1980s has altered local sediment pathways. The construction of buildings and seawalls along the coast has disrupted the natural "feeding" of the dune, starving it of new sand and accelerating erosion at its base. Between 2006 and 2023, the dune's peak lost 2.7 meters in height.
An Urban Obstacle Course
The movement of Morro do Careca directly threatens urbanized areas, particularly the nearby Alagamar neighborhood. The slow but relentless advance of sand threatens fixed infrastructure. In response to both the dune's migration and erosion from foot traffic, authorities took decisive action. In 1997, the dune was permanently closed to the public. Before the closure, it was a popular spot for recreational sandboarding, locally known as "esquibunda." The prohibition was an attempt to preserve the remaining stabilizing vegetation and slow the erosion that was visibly reducing the dune's height.
Early conservation efforts involved planting non-native vegetation, such as casuarina trees, to anchor the sand. This method of dune fixation has been attempted globally, often with mixed results. While vegetation can stabilize the surface, it also fundamentally alters the natural character of a mobile dune system. In the case of Morro do Careca, these interventions have not halted the underlying geological process. The system is now experiencing intensified erosion from rising sea levels and altered water drainage from recent beach nourishment projects, which creates gullies and carries sand away. A 2023 report from the Geological Survey of Brazil noted the intensification of erosion and a "very high" risk of landslides at the dune's base.