ancient cities

Introduction
We live in an urban world. For the first time in
human history, more than half of the world’s
population—some 3 billion persons—lives in
urban areas. In the next two decades the number
of persons living in urban areas will increase by
another 2 billion persons—an amazing 60 percent
increase—to 5 billion persons. The United Nations
estimates that by 2030, more than two-thirds of
total world population will live in urban areas.
Most of this increase will take place not in Europe
or in the United States, but in the megacities and
newly emerging urban regions of countries in
what used to be called the developing world.
These urban areas are linked in exciting and
new ways that would have been unimaginable just
a short time ago. We can text friends in other
countries for a fraction of the cost of a long-distance
telephone call, or SKYPE with family and
colleagues on the other side of the world for even
less. We are connected by a global economy where
the life opportunities of persons in one country
are dependent on capital flows of new investments
from nations on the other side of the world. The
mass media bring world music from Africa and
the Middle East to balance the spread of hip hop
and reggae. We use the Internet to make new
friends in places we have never even heard of. At
the beginning of the twenty-first century it is a
global world, to be sure, but more than that, it is,
for the very first time, an urban world.
The new urban world of the twenty-first century
is the object of study for our field, urban
Studies. There likely is no other more important
area of study, for if we are to solve the very significant
and growing problems of climate change
and global inequality, among others, we must
understand that these problems often are directly
associated with the growing urban populations
and cannot be solved without strategies that connect
urban regions across international borders:
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we know, for example, that the flow of undocumented
workers from Africa to Europe is the consequence
of economic disparities between these
regions. Urban studies is the field of study that
addresses both the growth and expansion of
urban areas (urbanization) as well as the nature of
and quality of urban life (urbanism)—the two
most pressing areas of inquiry for the coming
decades.
The specific areas of study in urban studies
include subfields of the many disciplines that
include the study of urban areas (such as urban
anthropology, urban economics, urban geography,
urban history, urban politics, urban psychology,
and urban sociology), professional fields such
as architecture and urban planning, and other
fields such as art, literature, and photography that
are situated within the built environment. Within
each of these subfields and interdisciplinary areas,
there are specific theories, key studies, and important
figures that have influenced not just the individual
discipline, but the field of urban studies
more generally. Indeed, not only is the field of
urban studies influenced by important work from
the urban disciplines, but the disciplinary subfields
themselves often share important bodies of
work and even research traditions. To give but
one example, the work of Henri Lefebvre has had
profound influence not just in his home discipline
of sociology, but in other disciplines including
geography and political science—and across urban
studies more generally.
In this encyclopedia, we have sought to include
important work and traditions from each of the
urban disciplines, but we also wanted to demonstrate
the international and interdisciplinary nature
of the field. To this end, we sought contributions
from scholars in many different countries. Because
certain areas of study have often been associated
with particular countries (suburbanization in the