ancient cities

514 Mexico City, Mexico
The Conservation Zone
Peripheral urbanization is placing extreme pressure on the immediate environment of the city and even jeopardizes
its sustainable future growth. Although peripheral expansion of the city is numerically greatest in the northern
and eastern regions of the metropolitan area, expansion to the south of the city has particularly significant
environmental impacts. There is a large conservation area to the south of the Federal District, which is a vital
environmental resource for a city so burdened with environmental problems, but which is threatened by illegal
settlement. It has been estimated that between 1967 and 1995, urban sprawl in the southern periphery of the
metropolitan area grew from 1,427 hectares to 11,896 hectares, which has implied a loss of 10,469 hectares of
conservation land. This is in spite of government programs established to protect the conservation zone.
During the early twentieth century, the wealthy
elite began gradually to move from the center
toward the southern and western zones of the city,
a process that continued throughout the century.
The island location of the original city meant
that its expansion had depended on the Aztecs
creating artificial land masses traversed by a system
of canals. While the expansion of the city
under such difficult conditions led to the development
of very advanced water treatment and
sanitation systems, a range of environmental difficulties
inherent to the relatively inhospitable terrain
have plagued the city as it has developed and
grown. The decimation of the city of Tenochtitlan
by the Spanish included the destruction of much of
the original infrastructure, which had been designed
to prevent flooding. From the colonial period
onward, poor land management and consequent
frequent flooding, together with demands for
expansion, made it necessary to gradually drain
the basin, such that present-day Mexico City is
built on top of much of the ancient lake bed.
The construction of a deep drainage system and
the drying out of the ancient lake beds meant that
the subsoil, which had been strengthened by
groundwater, became too weak to support the city
above it, and between 1910 and 1987, the city
center sank by about nine meters. The weakness
also proved catastrophic during the earthquake of
1985. In addition, a lack of water continues to
present a major problem for the city.
Another serious environmental concern is air
pollution, whereby geographic and climatic factors
hamper the dispersion of high levels of industrial
and vehicle pollution. Yet, a reduction in heavy
industry in Mexico City in recent years (itself in
fact partly a result of government incentives to
relocate away from the city), together with local
and federal government action to reduce levels of
pollution, have certainly had some effect.
Urban Planning and Administration
At the beginning of the 1970s, a shift toward
metropolitan expansion emerged as a new form of
urban growth in Mexico, which particularly affected
Mexico City. There was a massive rural–urban
migration flow, with about 3 million migrants moving
to Mexico City in the 1960s. This translated
into an annual growth rate of 5.7 percent, which
was an historic high at this time.
As the city has grown, it has absorbed many old
towns within its limits, particularly in the postrevolution
period from the 1920s. This process continues
to the present day, with more outlying towns
becoming absorbed into the sprawl of the city.
These ancient centers serve to provide the surrounding
population with an alternative to the city
center, in terms of supplying services, affordable
goods, and informal employment opportunities.
Thus, the growth of the city has been decentralized
to some extent, which has reduced the population’s
reliance on the city center, making the city more
efficient in meeting people’s basic needs. Indeed,
toward the end of the 1970s, support and development
of these alternative centers became an intentional
part of urban planning. Among the middle
classes, this has meant that the city center—once
the preferred shopping district—is losing out to an
increasing number of suburban shopping centers,
further challenging the relevance of the city center.