Deep beneath Mexico’s Yucatán Peninsula lies an intricate network of freshwater caves. In the isolation of the caves — created by the impact of the asteroid that killed the dinosaurs — endemic species have evolved to thrive in this one of a kind ecosystem. Once clear and abundant with life, these ancient caves, called cenotes, have sustained the region’s people and wildlife for thousands of years.

Decades of local sewage disposal and agricultural runoff have left cenotes vulnerable to species die-off and structural deterioration. However, these damages pale in comparison to the environmental threat of the Tren Maya, a 966-mile railroad loop around the coast of the Yucatán Peninsula. 

Since the Mexican government announced the project in 2018, there has been significant pushback , resulting in a national controversy over its economic advantages and ecological damages.

Overseen by Mexico’s National Fund for Tourism Development, construction of the train, which was often done without permits, has resulted in 16,455 acres of deforested land in the protected Maya Forest, thousands of pillars drilled into the ancient cenote systems, and about 3,000 displaced families.

Overseen by Mexico’s National Fund for Tourism Development, construction of the train, which was often done without permits, has resulted in 16,455 acres of deforested land in the protected Maya Forest, thousands of pillars drilled into the ancient cenote systems, and about 3,000 displaced families. 

On the other hand, the train does have significant economic benefits for rural communities. The United Nations estimated that the train would generate 900,000 new jobs and help 1.1 million people out of poverty by 2030. Considering the economic and environmental outcomes, it’s a double-edged sword for local communities who are now more vulnerable to freshwater pollution. 

Water quality consultant Guillermo D. Christy found elevated levels of E. coli and iron oxide in cenote waters. In a National Geographic article , he explained, “the stalactites — hundreds of mineral formations hanging like melted candle wax above us which naturally filtrate the rainwater —  are being clogged by cement dust.”

Polluted waters from construction flow throughout the interconnected network, contaminating the only natural freshwater supply available to hundreds of species, residents, and tourists. The pollution isn’t contained within the cenotes system; it seeps into the ocean, affecting coastal and rainforest ecosystems.

Polluted waters from construction flow throughout the interconnected network, contaminating the only natural freshwater supply available to hundreds of species, residents, and tourists. The pollution isn’t contained within the cenotes system; it seeps into the ocean, affecting coastal and rainforest ecosystems. 

For many environmental activists, local Indigenous communities, and scientists , the economic benefits aren’t enough to outweigh the environmental damages of illegal construction practices . Mexico’s National Fund for Tourism Development went ahead with building the railroad before it had the proper permits, land use approval, or conducted a technical and scientific study. The International Rights of Nature released a statement condemning the Tren Maya on the grounds that it would harm local “bio-cultural diversity that characterizes the southeastern region of Mexico.”  

A lawsuit in objection to the railway reached Mexico’s supreme court in 2023, resulting in the First District Court in Yucatán ordering the National Fund for Tourism Development to halt logging in areas that weren’t approved for a land use change. Construction paused until Mexico’s President Andrés Manuel López Obrador instructed the military to complete the project.

During a press event in April 2025, Mexico City officials acknowledged the environmental impact the Tren Maya has caused and announced that they were assessing wildlife crossing options, in addition to cenote and forest restoration methods. Alicia Bárcena from Mexico's Ministry of Environment and Natural Resources (SEMARNAT) said the destruction was “so comprehensive that reforestation is essential” and called upon local communities to “help us restore the forest ecosystem.” 

Despite their claims to facilitate restoration projects, the Mexican government revealed — in the same 2025 press event — plans to expand Tren Maya by adding 10 cargo ports and 44 miles of railway, in addition to the construction of about 630 miles of new railway systems. They did not address any environmental impacts the new railways will cause.  

SEMARNAT’s acknowledgement of the ecological destruction caused by the Tren Maya was a win for many conservationists who have been fighting the Mexican government for restoration projects. The expansion of railways will cause potentially irreversible environmental impacts, and studying those impacts is a challenge. With over 8,000 registered cenotes, researchers are racing the clock to map the maze of underground waterways and study the one-of-a-kind ecosystem that hosts species not found anywhere else on Earth.