332 Big pictures
greenspace interruption to facilitate crossing by wildlife. Particular effort for
maintaining species connectivity may be appropriate between two nearby cities,
which could become connected by future strip development along a highway.
The outer portion of the urban-region ring furthest from the city is especially
important for biodiversity protection. Mapping and evaluation of biodiversity
patterns both in this outer area and in nearby areas of adjoining regions is
important. Thus some species only in the region and some species primarily
just outside of it may be effectively protected long term. Urbanization around
outer satellite cities (Chapter8)poses a threat, so the particular areas urbanized
require careful planning, and concentric-zones urbanization around the major
city may be preferable.
In short, overall biodiversity loss on the planet will not be arrested in urban
regions. But in the face of huge increases in urban people in the next generation,
much can be done in these regions to protect their species and especially reduce
urban impacts on rare species of other regions.Waterscarcity
Humans keep growing in number and spreading out from cities over
theland. People want clean freshwater to drink and for domestic use. We also
need relatively clean freshwater for agricultural food production and for run-
ning industry. The planet operates with essentially a fixed amount of freshwater,
which effectively keeps recycling (in a hydrological cycle) through the atmo-
sphere, land, and sea. There seems to be no new freshwater to discover. With a
fixed amount and growing human usage, the cost of water is rapidly rising and
global water scarcity has arrived.
Water scarcityhitsusunevenly.People in dry climates suffer first and worst.
Prolonged droughts, dried-out vegetation, fires, wind erosion of soil, and atmo-
spheric dust are familiar refrains. Human-caused desertification, salinized soils,
and dropping water tables in the ground due to irrigation make headlines. But
waterscarcity also impacts urban regions, e.g., recent prolonged droughts in
Canberra, Atlanta, Nairobi, and Brasilia, where so many people are packed
together.
Cities are primarily surrounded by farmland in urban regions (Color Figures
2--39,andChapter6). To produce food products for the nearby population, and
because land prices are high, irrigation is widely used in urban-region agricul-
ture. Market-gardening near the metropolitan area is a classic example, where
ahigh production of vegetables and fruits continues often year-round.
Industry, another major water-user, characterizes and often dominates cities.
Forinstance, megacities in developing nations are effectively industrial cities.
Waterisused for cooling, and in some cases for power and waste disposal. Rising