Threats to Sac Actun: World’s Largest Underground River in Tulum Facing Peril

Nestled under the Yucatan Peninsula, the world's largest underground river, Sac Actun, spans an impressive 386 kilometers. This vast and intricate network of flooded caves, whose name translates to "white cave" in Maya, is located in the Tulum municipality. Its length exceeds 368 kilometers with depths reaching up to 120 meters. Sac Actun is home to a rich biodiversity and holds immense archaeological value, with discoveries dating back to the Pleistocene era and remnants of a civilization that existed 8,000 years before the Mayan Empire. The river system boasts over 220 cenotes, which serve as access points and connections to the external world.

Despite its ecological and cultural significance, Sac Actun is under threat from various human activities. These threats are particularly concerning as Sac Actun's groundwater also nourishes the Mesoamerican Reef System, the world's second-largest coral reef, which supports an exceptional marine biodiversity.

1. Urban and Tourist Development: Rapid urban expansion, particularly in cities like Tulum, is a major issue. Unplanned construction of infrastructure, hotels, and tourist resorts has led to deforestation and soil alteration, which directly impacts the integrity of the cave system. Additionally, inefficient drainage and wastewater treatment systems have resulted in pollutants infiltrating the aquifer, posing a risk to the water quality and dependent biodiversity.

2. Large Scale Infrastructure Projects: The Tren Maya railway project, which connects various regions of the Mexican southeast, has raised concerns among environmentalists and scientists. Parts of this construction cut across sensitive areas of the Sac Actun system. The installation of pillars and rail tracks over the caves could potentially cause collapses, disrupt groundwater flows, and fragment critical habitats for endangered species, such as the jaguar.

3. Aquifer Pollution: The constant threat of untreated wastewater infiltration is alarming. Pollution from nitrates, phosphates, and other chemical compounds can lead to algal blooms and affect water quality, endangering both human health and ecosystems dependent on the aquifer.

Protection of Sac Actun falls under the jurisdiction of several government agencies at the federal, state, and municipal level, including the National Water Commission (CONAGUA). CONAGUA is responsible for managing and preserving water resources in Mexico, and is tasked with regulating water use and ensuring its quality. However, the effective implementation of protection policies has been limited, and more stringent surveillance and regulation enforcement are necessary to prevent pollution and overexploitation of the aquifer.

The National Commission of Protected Natural Areas (CONANP) is tasked with conserving ecosystems and biodiversity in protected areas. Despite Sac Actun being part of the Sian Ka’an Biosphere Reserve, the pressures from tourist development and projects like the Tren Maya have cast doubt on the effectiveness of current protection measures. It's crucial that CONANP enhances its conservation efforts and collaborates with other institutions to mitigate the impact.