Mexico City’s ancient Xochimilco floating gardens are in ecological peril

The once great floating gardens of Mexico City, which filled the bellies of the Aztecs, are dying of serious neglect.

On this point, everyone sadly agrees.

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The ancient plots and their life-giving canals are weedy and abandoned, overrun by cattle, invaded by exotic fish, sucked dry by urban sprawl — and a dozen agencies of government have failed to save one of the wonders of the world.

A few farmers continue to till their little corners of Eden. They grow marigolds for El Dia de los Muertos, the Day of the Dead.

“Which is appropriate,” said Luis Zambrano, a biologist at the National Autonomous University of Mexico, who is trying to save the indigenous life of Xochimilco, “since the place is dying.”

The gardens have been sick for a long time, ever since the Spanish conquistador Hernan Cortes arrived in 1519 and began draining the lakes.

The problem is that they are now dying quickly, and there are worrying signs that the ecosystem is crashing.

Asked whether the place can survive, a respected historian of Xochimilco, Gloria Valek, answered, “I would like to think so, but it might be impossible.”

The canals that once fed 50 square miles of gardens are overwhelmed by foreign fish, African tilapia or Asian carp, thriving in the dirty waters. The fish are loaded with heavy metals, fed by wastewater treatment facilities — the lake’s only water source, now that the 2,500 artesian springs have dried up, trying to slake the thirst of the megacity. Maybe half the original wetlands used by the Aztec vassals here remain, much of them degraded. But the land could bounce back.

Fisherman Roberto Altamirano has been working to save Xochimilco (pronounced so-chi-MIL-co), which is a U.N. World Heritage Site. For two years, he has been netting exotic species from the canals. “We have removed 650 tons of fish,” he said, “which is a lot of fish.”

But people don’t want to buy the tilapia and carp the fishermen net when they learn they come from Xochimilco, which has a bad reputation because of the pollution.

In one of the experimental reserves, the farmers had to stop using the tilapia as fertilizer — because they were too toxic.

The Valley of Mexico is a bowl surrounded by mountains and volcanoes. The Aztecs built their empire in the middle of a series of interconnected lakes. Their capital of palaces and pyramids, Tenochtitlan, reached by causeways, was an amazing sight to the conquistadors, who said it was more impressive than any city in Europe.

For a thousand years, farmers staked out small rectangular plots in the shallow lakes around the Aztec capital. They built their artificial islands of wattle and willow and filled the gardens, called chinampas, with fertile muck.

The farms were irrigated by an immense grid of miles of shallow canals, just wide enough for a canoe. The gardens produced a bounty: five or six crops a year, an abundance of chiles, greens, cactus and herbs. The canals were exploited for crayfish, frogs, fowl, fish.

It was an ingenious system, and what is amazing is that a visitor can see a glimpse of the old ways even today.