334 Big pictures
theland, thus reducing water recharge into the groundwater. That commonly
results in contaminated water and a lowered water table under and around
metropolitan areas.
An extensive wooded area upwind of an urban region evapo-transpires water
into the atmosphere. When cooled, the moist air may produce rain for the
urban region and its groundwater. Air pollutants from the urban region in turn
may include particles and aerosols around which the moist-air water molecules
coalesce, producing rain both in the region and downwind of it. Thus deforesta-
tion, overgrazing, or desertification of the broad upwind area may contribute to
drying out of an urban region.
These threads suggest three issues linking water scarcity and urban regions.
The growing worldwide scarcity of freshwater causes increasingly severe limi-
tations and costs on clean water supplies for most urban regions. The concen-
tration of people and water uses in urban regions in turn is accentuating the
global water scarcity. These reciprocal challenges seem headed for crisis as urban
populations are expected to skyrocket in the years just ahead.Big-ideas--regulations--treaties--policy--governance, megacities,
sense of place
This umbrella of big pictures highlights strong social and cultural
connections. The first topic, ‘‘Big-ideas--regulation--treaties--policy--governance,”
introduces the human forces that help determine how an urban region is main-
tained and changed. Then ‘‘Megacities” are examined as the largest human con-
centrations on Earth. Finally, ‘‘Sense of place” considers a compelling way to
bring the giant urban-regions topic to the scale of a person.Big ideas--regulations--treaties--policy--governance
Asequenceofbigideasprovidesauseful framework for urban-region
environmental issues, which in turn lead to the regulatory approaches and
policy that help to govern human behavior. Consider an overlapping sequence
ofbig ideasthrough history (McNeill2000): religion (in diverse forms), ratio-
nalism/science, nationalism, hard-work-making-land-productive (or rural righ-
teousness), and communism. After about 1940, economic growth, with roots in
ancient China, Europe and elsewhere, became perhaps the most powerful idea
of the twentieth century. Embraced by capitalists and communists alike, the
economic growth idea transformed society’s focus, relegating land and natural
systems to the status of background source of resources for growth.
Environmental ideas, again deeply rooted in history, overall mattered little
tosociety until the 1970s catalyst of Rachel Carson’sSilent Spring(Buell1995).