projects for low-income residents. Moscow, Los Angeles, Buenos Aires, Kolkata,
and Tokyo achieved the highest population growth rates from 1900 to 1950.
New York was the only city to surpass 10 million people (within the metropolitan area) and become a megacity in the 1930s. Although the populations of
Paris and London grew significantly in the nineteenth century, these two cities in
upper Eurasia did not become megacities during the first half of the twentieth
century. The reason for this may be that they had high-density historic areas from
before the premodern era, which were retained even after they undertook urban
remodeling in the last half of the nineteenth century, and there was a clear divide
between their urban areas and suburbs. These features were based on the urban
tradition of upper Eurasia, which in turn was influenced by the forms of the
mid-latitude arid region.
The third condition for the emergence of megacities was the development of
sanitary engineering, together with new urban planning, which occurred in upper
Eurasia and North America and Oceania. It was essential to solve the urban
problems caused by the rapidly increasing population in the nineteenth century,
which arose as a result of the second condition, i.e., industrialization, and it was
well supplied in the 18 cities in the early twentieth century through the global
system, which was the first condition as above. The development of sanitary
engineering enabled cities to increase their habitable population density beyond
the arid areas, including in tropical and frigid areas. To metropolitanize a city, it
was necessary to develop civil engineering infrastructure, typically highways,
and full public sanitary facilities with water and sewer services. Cities came to be
supported by sanitary engineering and urban planning at the same time as the
modern idea of a city based on democracy and capitalism became prevalent in
Europe and America.
In Europe, based on the experience of being bombed during the wars or on
local urban traditions, the concept of modern cities was gradually changing
direction, with an emphasis on developing less-populated cities. After 1950,
this trend also became evident in North America and Oceania. This change in
direction may have been caused by the declining birthrate or by the increase in
economic standards, which led to production bases, such as factories, being
moved to rural areas or overseas, and increased the number of middle-class
citizens engaging in the tertiary sectors.
4. The fourth condition, the power of nation states After WWII, urban areas and
populations grew at an unprecedented rate in the mid-latitude arid region and
monsoon Asia, where many nation states were independent. The 1980
populations were more than four times as high as those of 1950 in Dhaka,
Seoul, Sao Paulo, Karachi, Jakarta, and Delhi. During this period, many workers
relocated from small towns to the primary cities of nation states, where they lived
in densely populated residential areas based on traditional designs. Middle- and
high-income people relocated to newly developed residential areas in the suburbs.
Residences in the historical city centers dwindled. In Latin America, nation states
were formed from the early nineteenth century but, as industrial and economic
5 Regional Diversity and Sustainability of Megacities in Global Historical. . .
93
and Tokyo achieved the highest population growth rates from 1900 to 1950.
New York was the only city to surpass 10 million people (within the metropolitan area) and become a megacity in the 1930s. Although the populations of
Paris and London grew significantly in the nineteenth century, these two cities in
upper Eurasia did not become megacities during the first half of the twentieth
century. The reason for this may be that they had high-density historic areas from
before the premodern era, which were retained even after they undertook urban
remodeling in the last half of the nineteenth century, and there was a clear divide
between their urban areas and suburbs. These features were based on the urban
tradition of upper Eurasia, which in turn was influenced by the forms of the
mid-latitude arid region.
The third condition for the emergence of megacities was the development of
sanitary engineering, together with new urban planning, which occurred in upper
Eurasia and North America and Oceania. It was essential to solve the urban
problems caused by the rapidly increasing population in the nineteenth century,
which arose as a result of the second condition, i.e., industrialization, and it was
well supplied in the 18 cities in the early twentieth century through the global
system, which was the first condition as above. The development of sanitary
engineering enabled cities to increase their habitable population density beyond
the arid areas, including in tropical and frigid areas. To metropolitanize a city, it
was necessary to develop civil engineering infrastructure, typically highways,
and full public sanitary facilities with water and sewer services. Cities came to be
supported by sanitary engineering and urban planning at the same time as the
modern idea of a city based on democracy and capitalism became prevalent in
Europe and America.
In Europe, based on the experience of being bombed during the wars or on
local urban traditions, the concept of modern cities was gradually changing
direction, with an emphasis on developing less-populated cities. After 1950,
this trend also became evident in North America and Oceania. This change in
direction may have been caused by the declining birthrate or by the increase in
economic standards, which led to production bases, such as factories, being
moved to rural areas or overseas, and increased the number of middle-class
citizens engaging in the tertiary sectors.
4. The fourth condition, the power of nation states After WWII, urban areas and
populations grew at an unprecedented rate in the mid-latitude arid region and
monsoon Asia, where many nation states were independent. The 1980
populations were more than four times as high as those of 1950 in Dhaka,
Seoul, Sao Paulo, Karachi, Jakarta, and Delhi. During this period, many workers
relocated from small towns to the primary cities of nation states, where they lived
in densely populated residential areas based on traditional designs. Middle- and
high-income people relocated to newly developed residential areas in the suburbs.
Residences in the historical city centers dwindled. In Latin America, nation states
were formed from the early nineteenth century but, as industrial and economic
5 Regional Diversity and Sustainability of Megacities in Global Historical. . .
93