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Mexican President, Andres manuale López Obrador, is unveiling a new multibillion dollar rail network called the Tren Maya. It's forecast to bring an additional two million more tourists to the impoverished Yucatán Peninsula every year, but it's run massively over budget and critics say it's an environmental catastrophe. Will Grant, reports from Southern Mexico. To the.

Ancient Maya, the sonotes of the Yucatán Peninsula were sacred, portals to the underwater and one of the most unspoiled freshwater ecosystems in the Americas. But directly above them is this, the Mexican President's pet infrastructure project, the Trenmae, a 1,500 kilometer long rail link to bring tourism to the jungle. Environmentalists are horrified. The deforestation alone has destroyed fragile habitats for jaguars and macaws. Activists took us into the labyrinth below to show another environmental cost, water pollution.

Once the water gets polluted, no life will be able to be sustained in.

This area. I mean, is it no exaggeration to say essentially what's going on above the surface is killing what's going on.

Beneath the surface?

For sure, definitely.

The team takes readings to see where water quality is getting worse. They say the stallactites, which naturally filtrationrainwater, are being clogged by cement dust.

So putting something as huge and as destructive as the Trenmae, a massive man-made construction, is obviously going to have a huge impact. But it's also all the other things that come with it. The arrival of millions of tourists, the movement of material and fuel, all of it will hurt this subterrain ecosystem.

Above ground, the Trenmae has divided communities. This one, Vida e Esperanza, has been dissected by a maintenance station. Some were well compensated for their land, but Benjamin-Chim had his fields dynamited and turned into a quarry. He received nothing for them as like many Maya farmers, he couldn't prove ownership. We'd worked this land for 40 years. I applied for the deeds but never received them, he explains. As he test drove the train, President Lopes Obrador calls it the greatest construction in the world. But the line from Cancun South changed mid-construction after pressure from luxury hotels. Activists fear surveys were rushed and the elevated track could collapse. Nonsense, says its director.

Prenmae is a great, great infrastructure. Every Mexican, every tourist, international tourists transporting themselves in our train, they will be safe.

These cinotes are archeological gems, burial sites of some of the first peoples of the Americas. The Trenmae will bring more tourists to the Yakitan, but the rush to develop could also ruin the hidden treasures upon which the region was founded. Will Grant, BBC News, the Yakitan Peninsula.