The community of Nicolás Bravo, Chetumal reported a rumble and a roar. At that moment, a nearby lagoon, known as Laguna de Chakanbacán and totaling roughly one square mile, was draining like a bathtub. Three quarters of its water would eventually disappear, consumed by a trio of sinkholes that left only a muddy expanse and stench of putrefying animals.
Dispatches this month from Chetumal, capital of the Mexican state Quintana Roo, situated on the tropical Yucatán Peninsula, claimed that sinkholes— socavones—had gulped down a local lagoon in mere days. The natural phenomenon, according to investigations conducted by Mexico’s environmental agencies, may be the fault of “cavernous structures” that lie beneath the coastal region. A labyrinth of tunnels and cave systems, many of which are flooded, can host otherworldly ecosystems and archaeological relics. And because of the Yucatán Peninsula’s unique geology, a spokesperson from Comisión Nacional del Agua (Mexico’s national water commission) told Mexican newspaper La Jornada last week, “underground currents” possibly eroded the top layer of a tunnel system underneath the lagoon, opening and draining its contents into three tunnels, one thirty-two feet in diameter.
“The world's densest known accumulation of flooded cave passages are found in the northern part of Quintana Roo along the Caribbean coast,” David Brankovits, a postdoctoral scholar at Woods Hole Oceanographic Institution who explored the underwater Ox Bel Ha cave system in the Yucatán Peninsula—the longest of its kind—told me in an email. “Here, more than 1000 kilometers [more than 620 miles] of cave conduits have been mapped by cave diving explorers and exploration efforts are still underway.”
The peninsula itself is a large karst platform, Brankovits added, which is more or less eroded limestone. “Caves are accessed through natural sinkholes or, as locally called, cenotes,” he said. These systems play a pivotal role in how water is distributed throughout the region. Above-ground bodies of water, such as lakes and ponds, are generally uncommon there. Instead, water tends to move underground, giving rise to underground rivers, as “permeable limestone bedrock allows water to infiltrate the ground.”
Still, the site of Laguna de Chakanbacán is less known for its cave passages, Brankovits noted. “Perhaps there was an impermeable geological layer below the lake that was ‘punctured’ with the collapse causing the water to drain underground,” he said, possibly indicating that “cavernous geology” is still evolving throughout the local landscape.
Pools reaching depths of twenty feet are now visible from the surface, La Jornada reported.
Before and after photos were posted to Facebook by one Quintana Roo resident. Some locals are worried that farming and agriculture may suffer from a depleted water supply. Quintana Roo’s economy also depends on ecotourism, and Laguna de Chakanbacán was part of an upcoming archaeological zone the state hoped would attract tourists.
“The cenotes as karst windows expose the groundwater,” Brankovits explained. “Historically, such cenotes were one of the most important source of drinking water for human populations.”
Laguna de Chakanbacán’s water wasn’t the only loss. Decaying fish, turtles, and eels are reportedly the source of an odor there. La Jordana claims that opportunistic looters are even pillaging the stranded wildlife, and that a local militia now stands guard. Some of the lagoon’s animals, however, like the Morelet’s crocodile or cocodrilo de pantano, may have successfully moved to another habitat, and environmental agencies say the overall impact on fauna was minimal.
As Brankovits’ expeditions have shown, the Yucatán Peninsula’s cave systems are home to unique and vibrant ecosystems. “An entire food web exists in the caves below the dry tropical forests,” he described. “This food web includes microbes and cave-adapted animals, both invertebrates and vertebrates. Life has adapted to the dark and energy-limited cave environment,” such as blind fish and crustaceans without pigment that flourish in seemingly spartan habitats.
As for Laguna de Chakanbacán and its inhabitants, “sinkholes have been forming in the Yucatan ever since there are caves underground,” Brankovits added. Mexico’s Federal Agency of Environmental Protection did not respond to a request for comment regarding the status of its investigation into the cause of the sinkholes.
“Because caves are ‘out of sight, out of mind,’ they are often considered as unique but insignificant features of nature,” Brankovits said. “However, the truth is that they greatly influence our environment, even on the surface where we live.”