Mexico City - Environment

Environment

See also: Water management in Greater Mexico City

Originally, much of the valley laid beneath the waters of Lake Texcoco, a system of interconnected saline and freshwater lakes. The Aztecs built dikes to separate the fresh water used to raise crops in chinampas and to prevent recurrent floods. These dikes were destroyed during the siege of Tenochtitlan, and during colonial times the Spanish regularly drained the lake to prevent floods. Only a small section of the original lake remains, located outside the Federal District, in the municipality of Atenco, State of Mexico. In recent years, architects Teodoro González de León and Alberto Kalach, along with a group of Mexican urbanists, engineers and biologists, have developed the project plan for Recovering the City of Lakes. The project, if approved by the government, will contribute to the supply of water from natural sources to the Valley of Mexico, the creation of new natural spaces, a great improvement in air quality, and greater population establishment planning.

The federal and local governments have implemented numerous plans to alleviate the problem of air pollution (such as carbon monoxide), including the constant monitoring and reporting of environmental conditions, such as ozone and nitrogen oxides. If the levels of these two pollutants reach critical levels, contingency actions are implemented which may include closing factories, changing school hours, and extending the A day without a car program to two days of the week. To control air pollution, the government has instituted industrial technology improvements, a strict biannual vehicle emission inspection and the reformulation of gasoline and diesel fuels. Data from the city's 36 air-quality monitoring stations show lead levels down 95 percent since 1990, while sulfur dioxide has fallen 86 percent, carbon monoxide 74 percent, and peak ozone levels 57 percent since 1991. In 1990, Patricia Saad Sotomayor reported in the Mexico City daily Excélsior that "100,000 children die every year as a result of pollution in the Mexico City metropolitan area, 250,000 people suffer from eye diseases..and life expectancy has been reduced by up to ten years, according to the National Environmentalist Groups." in a report to President Salinas. At the time, according to the United Nations pollution scale "which set 100 as the maximum level before grave health problems begin", Mexico City's level was 97.5, compared to 4.5 for New York City, and 2.5 for Milan, Turin, and Los Angeles.

In 1986, the non-urban forest areas of the southern boroughs were declared National Ecological Reserves by president Miguel de la Madrid Hurtado. Other areas of the Federal District became protected over the following years.