Restoring the Floating Gardens
The Floating Gardens of Xochimilco are in the middle of Mexico
City. It's a place to spend a few leisurely hours drifting
on a network of ancient canals. But, hidden from view, away
from all the musicians and all the vendors, is a world rarely
seen by outsiders.
This is what much of Mexico City looked like 600 years ago
when it was founded on an island in the middle of a lake.
Like their Aztec ancestors, farmers created land by piling
mud along the shores. These man-made fields, called Chinampas,
are highly productive because water seeps up through the mud
and keeps the soil moist during the dry months.
The Chinampas are a delicate eco-system requiring the one
commodity that Mexico City cannot spare: fresh water. Over
the years, a series of local springs were depleted and polluted
water flowed into the canals.
The farmers of the Chinampas decided to do something about
it. Their goal was to save some of the most productive land
in the world, where the soil is so fertile it can yield as
many as ten harvests a year. Recently, they convinced the
authorities to allow a combination of fresh and treated water
to flow back into these canals.
For the farmers who work these small plots of land, their
success reflects Mexico City's spirit of survival.
Mexico City pulses with energy. It's an ancient gathering place layered
with a rich history of indigenous and Spanish cultures a nation's
capital where pilgrims come seeking miracles and offer prayers of
gratitude. It's also a twenty-four hour a day, high-octane city that
Street performer in Mexico City
Home to over 20 million citizens and growing by 350,000 each year, living conditions are so serious that a 200-year-old celebration in praise of liberty is often marked by angry demonstrations demanding environmental action.
How did this happen? How could such a proud and beautiful city become a metaphor for all that could go wrong with urban development?
Computer-generated models help visualize the city's fundamental problem.
Mexico City is located in a valley a mile and half above sea level.
Surrounded by a wall of mountains, some as high as 12,000 feet, it's
locked into what scientists call a closed eco-system. Unlike most
other mega-cities there is little wind to cleanse the air and no ocean
or major river to exchange water and sewage.
How could such a proud and beautiful city become a metaphor for all that could go wrong with urban development?
The city's atmosphere is thick with smog; a toxic soup cooking airborne chemicals into ozone. Eight out of ten days are declared hazardous to human health. Just breathing is said to be the equivalent of smoking two packs of cigarettes a day. Adding to the problem are 35,000 factories spewing tons of pollutants into the air.
But it's primarily the emissions from over three million cars that leave the city gasping for breath. Mexico City is trapped between the limitations of its geography and a way of life shaped by the internal combustion engine. Yet the city struggles towards a cleaner future. Thousands of repair shops cater to stricter exhaust regulations and increased auto inspections.
Video Excerpt: Mexico City pulses with energy but thanks to its geography, population and the internal combustion engine, it is on the verge of environmental disaster.
[ 56k ] [ 220k ]
To encourage residents to use public transportation, the rapid transit system has been greatly expanded. Unfortunately, city officials have been forced to use much of their limited resources to deal with a more serious crisis. In a city famous for its richly decorated fountains, Mexico City is running out of water.
When the Aztecs founded the city, it was dotted with lakes and surrounded
by a densely forested watershed. Today only a few groves of trees
remain. The lakes are also gone, drained by the Spanish to expand
the city. In their place are 1400 square miles of asphalt and concrete,
and the remains of ancient aqueducts that once brought in water from
nearby springs. But as the city's population grew, more water was
Villagers work to clean up their neighborhood
The brief rainy season offers little help and the nearest river is on the other side of the mountains. Though Mexico City sits on top of a vast aquifer it's in danger of running dry because 70 percent of the city's drinking water is pumped from the underground reservoir.
As water continues to be consumed the aquifer loses volume, causing the land that rests on top to slowly collapse. Much of Mexico City's center has sunk more than 30 feet in the last century and is sinking another one to three inches a year.
Compounding the problem are open canals cutting through the heart
of the city. Each day, they carry billions of gallons of raw sewage.
Spreading foul odors and disease, the waste water is pumped over the
mountains, away from the city.
Every few years tainted river water from Mexico City brings cholera to the Mezquital valley. It's a deadly trade-off most farmers have reluctantly accepted.
Sixty years ago the Mezquital Valley was an arid wasteland. Today it's a fertile oasis because farmers, desperate for water, use the city's untreated sewage from the Tula River to irrigate their crops. Every few years, however, the tainted water brings cholera to the valley. It's a deadly trade-off most of these farmers have reluctantly accepted.
Construction crews are now working to correct the problem by expanding Mexico City's network of deep drainage tunnels. When completed, this underground passage will be filled with raw sewage. It's part of a massive construction project that will eventually eliminate all open sewage canals. The project's long-term goal is to treat the city's raw sewage before it ever reaches the Mezquital Valley. Though only ten percent of the city's wastewater now passes through new purification tanks, it's at least a start.
The lesson of Mexico City is simple. Despite all its history, all its efforts, the devastating consequences of uncontrolled growth serve as an environmental warning to the rest of the world.