338 Big pictures
(6) Contracts between separate governments: addresses specialized issues/
functions, provides economy of scale, and does not require state leg-
islation.In the evolution of big ideas, couldurban-region planningburst forth as the
next big one? Motivators are there in the public mind -- urbanization, sprawl,
traffic, shrinking water supply, rising sea level, squatter settlements, not-in-my-
backyard, and much more. Solutions targeted to the city or metro area are
welcome, but are generally band-aids -- too small and temporary. What will cat-
apult urban regions and environmental planning together as the big solution
in the public eye?Megacities
Cities with a population exceeding 10 million (or 8 million) seem to be
in a class of their own, not just quantitatively, but qualitatively. Putting aside
thequestion of what area is included in a population estimate, the number of
megacities with >10 million people has clearly accelerated over the past half-
century (World Urbanization Prospects2001):
If an agglomeration (city and adjacent, or nearly so, cities around it) with
>10 million is considered, the number rises to 23, with the addition of
Seoul, Cairo, Moscow, London, Tehran, and Istanbul. Another analysis high-
lights 22 megacities, adding Paris and Lagos, while dropping Dhaka, Beijing,
and Istanbul (McNeill2000). The United Nations Population Division lists 20
such urban agglomerations in 2005: the 17 above plus Cairo, Lagos, and
Moscow.
Noobvious groupings of megacities stand out. More than half are near the
sea and have considerable low-lying area subject to flooding. Several are in
basins or other locations that accentuate air pollution problems (Los Angeles,
Beijing, Mexico City). However, the usual way to divide megacities is their pres-
ence in developing nations (Jakarta, Dhaka, Cairo) and developed nations (Tokyo,
NewYork, London). Before briefly considering major environmental dimensions,
it is well to note that megacities also illustrate characteristics of cities in