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Friday, July 10, 2020
MEXICO CITY, Jul 27 2009 (IPS) - In Mexico City there are more than 8,000 square meters of public building rooftops covered with vegetation. This novel approach for bringing green to the cities is now reaching hospitals and kindergartens.
Eight months ago, the first “nature” roof was installed at the Belisario Domínguez Hospital, in Mexico City, in the Iztapalapa district. With 1.8 million inhabitants, it is the country's most densely populated area.
The green roof of this three-storey hospital is divided in two: the larger is over a portion of the first storey, the smaller is over the third.
“Having direct or visual contact with a green area helps a great deal in the patients' recovery. In Japan, nearly every hospital has a 'nature' terrace,” Tania Müller, head of the project, said in an interview.
According to the hospital's director, Osvaldo González La Riviere, “the workers enjoy the space. Initially, the smokers used it, but we have been able to regulate that. Some patients found out about it and now they ask to go for a stroll there, with the help of family members.”
Installation of such a roof requires a waterproof treatment that prevents roots from taking hold in the building material, and then there is a polyethylene layer to prevent runoff. A geotextile product is added to prevent fine particulate of the underlayer from reaching the roof itself.
And finally, the underlayer is put in place, a mix of volcanic stone material, lighter than soil, and organ material to feed the plants, which are then planted on top. It is not necessary to water the plants.
One section of the hospital's green roof is alongside the gynecological/obstetric ward. For the women who have just given birth, “it is more pleasing to look out the window to see nature than see a vending cart or a truck emitting exhaust,” said Evangelina Sandoval, the deputy medical director.
Also, “working with patients and confronting death produces stress. Now, instead of leaving by their usual route, many workers now use the emergency exits in order to pass through the roof garden,” she said. The hospital employs about 1,000 people.
The green roof measures 1,000 square meters – one-tenth the total roof area of the hospital. The area was transformed from a concrete space to a lush place that attracts bees, butterflies and birds, standing in stark contrast to the dense traffic and the concrete structures surrounding it. Three native species from the Valley of Mexico were planted there. “All are sedums (leaf succulents), of the Crassulaceae family,” explained Müller, director of urban, park and bikeway reforestation for Mexico City.
The heat from “a normal rooftop can reach 80 degrees Celsius, contributing to the 'heat-island effect' (the increase in temperature in urban areas with few green spaces and lots of pavement), especially in a city as urbanized as this one,” she said.
With the vegetation, the roof's temperature is maintained at 25 degrees Celsius, creating a microclimate that returns moisture to the environment and retains dust and particulate matter that could otherwise harm people's lungs, Müller added.
Furthermore, it won't be necessary to re-waterproof the roof for 80 years.
That is why the Secretariat of Health gave the Mexico City government the green light to create green roofs for its 28 hospitals.
All of this “is viable, but we need resources,” said Müller. “Everywhere budgets have had to be adjusted, and that is what we are evaluating.”
Planting a rooftop can cost 95 dollars per square meter, whether in Mexico, Europe or the United States.
But the positive results are obvious. Take the Center for Child Development (CENDI), which provides services for 400 children of the city's subway train workers, and is located in Mexico City's historic central district.
“Fifty percent of the city's chickens are concentrated in the surrounding blocks, which causes heavy soil and air pollution. In addition, there is traffic and a high crime rate,” said CENDI director Nadia Tapia.
Even so, this kindergarten has generated many of the cutting-edge programs that are ultimately implemented nationwide. In keeping with this trend, in mid-2008, the city government inaugurated a green rooftop – 1,190 square meters – on this two-storey building.
Since then, once the children reach the age of two they are introduced to the roof garden. Those ages three to six practice gardening skills in a small plot, where they make compost, and grow tomatoes, potatoes, parsley, chamomile and cactus.
“The children relax, they explore and they are more calm and cooperative when they reach the teaching area, increasing their capacity to learn,” said CENDI pediatric expert Araceli Becerra.
These children, explained the director, come from low-income families. “Seventy-five percent live in very small apartments, and because of crime concerns, they don't have access to parks.”
When they visit the rooftop, “they get excited and they want to touch and observe everything,” teacher Rosa Muñoz said in an interview for this article.
According to Müller, the green roofs are an “alternative for sustainable urban development, especially in a city like this, where even if we wanted to create a ground-level park, there is no place to do so.”
In the cities of Latin America, the average for green areas overall is 3.5 square meters per person. The World Health Organization recommends nine to 12 square meters per person.
“In Mexico City, we would have nine million more square meters of green space if we put one green square meter on every roof,” said Alberto Fabela, who is in charge of the roof at the Secretariat of Urban Development and Housing (SEDUVI).
Since April 2008, the SEDUVI six-storey public building has set aside 900 square meters of its roof for green space. The technique employed here is hydroponics — growing plants suspended in water.
So far, it has produced about 21,000 ornamental plants, donated to the districts of Coyoacán and Azcapotzalco, where they adorn gardens and median areas of their boulevards.
Geranium, marigolds, kalanchoe, petunia: “all strong and resistant to stress of the streets: cars, noise, smog, people,” said Fabela.
The plants are produced with the help of the 800 SEDUVI employees, who have the option of dedicating one hour of their workweek to maintaining, sowing or transplanting the flowers.
“We teach them to remove wilted leaves and to sow seeds. Obviously, it is a sort of therapy. We give them one hour, but the time passes quickly. The most receptive are the young people, 18 to 25, and elderly women,” Fabela added.
The capital government hopes that the more than 8,000 square meters of green roofs created so far in public buildings will serve as an example for the private sector.
For now, the city plans to ask businesses requesting construction permits to dedicate 10 to 20 percent of their rooftops to green space – in exchange for tax benefits.
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