283
Toluca was once a picturesque old
town to the west of Mexico City. Now
a city of more than 800,000 people, it is
gradually merging into the sprawl of
Mexico City—at a high ecological cost.See also: Pollution 230–235 ■ Endangered habitats 236–239 ■ Deforestation 254–259 ■ Depletion of natural resources
262–265 ■ Amphibian viruses 280THE HUMAN FACTOR
The area of the world currently
covered in urban development
is one-and-a-half times the size
of France. Mexico City has expanded
more than any other city in the West.
Spreading far beyond its official
boundaries to become the home
of more than 21 million people, it
has also grown disproportionately:
in 1970–2000, the surface area of the
city grew 1.5 times faster than its
population. While 59 percent of the
city’s territory is conservation land,
illegal logging and urban sprawl
continue to degrade urban forest,
grassland, and water supplies.
It is estimated that 37 percent
of all urban growth by 2050 will
occur in China, India, and Nigeria
alone. In Beijing and other cities in
China, densely populated hutongs
(alleyways), where the urban poor
used to live, are being demolished
to make way for low-density luxuryblocks, pushing the city limits—
and the urban poor—far from city
centers. The reliance on cars in the
new neighborhoods, and the lack of
central hubs, means there is little
opportunity for community life.
Aware of the problems caused
by urbanization, the Chinese
government is now trying to limit
the population of Shanghai to 25The endangered axolotl One of the victims of the urban
sprawl of Mexico City has been
the tiny axolotl, a pale-colored
salamander that looks like a fish
but is actually an amphibian,
and is sometimes known as the
Mexican walking fish. Capable of
growing up to 1 ft (30 cm) long, the
axolotl feeds on aquatic insects,
small fish, and crustaceans, and
has the ability to regenerate
severed limbs—a quality that
has made captive specimens an
important subject of scientific
research. The captive version is
also a familiar pet in aquariums
around the world.Historically, the wild axolotl
lived in the urban canals created
by the Aztecs as they built their
capital city in the 13th century,
and in the network of lakes
around the city that fed these
canals. As Mexico City has
expanded, these canals have
been lost, and the wild axolotl
has declined. In 2006, it was
added to the list of critically
endangered species and by
2015 it was thought that the
creature may have been extinct.
However, specimens have since
been found in Lake Xochimilco
in southern Mexico City.million and that of Beijing to 23
million by restricting land available
for building and controlling the
inflow of people, forcing out
low-skilled workers. China is
also building higher-density
neighborhoods with narrower
streets, more intersections, and
more public transport that will help
the formation of communities. ■US_282-283_Urban_sprawl.indd 283 12/11/18 6:26 PM