328 Big pictures
providing suitable locations for many or most terrestrial species to live. As
climate warms or cools, species move and relocate in emeralds with suitable
conditions. Vegetated corridors that connect the emeralds facilitate the move-
ment of many, though not all, species (Noss 2003). In effect, the emerald network
provides flexibility, redundancy, and stability in a changing world.
An alternative oft-proposed biodiversity solution is a major north--south cor-
ridor. This would facilitate species movement in response to changing temper-
ature. Unfortunately a corridor is simply too narrow as a habitat to effectively
support numerous key species. Furthermore a narrow habitat or strip is diffi-
cult to protect and sustain long term in an urban region, where nearby people
are numerous, human activities extensive, and ongoing outward urbanization
expected.
Sea-level rise,resulting mainly from continued melting of the Arctic ice cap,
Greenland, and Antarctic shelves, is the second major effect of climate change.
Sea-level rises of 0.5 to 5+ m (based on ice volume subject to melting) are com-
monly predicted by specialists, though the rate of melt is difficult to estimate
(new data and new processes discovered keep increasing the projected rate). In
any event, low-lying coastal areas are likely to be inundated. Coastal cities com-
prise a major proportion of the world’s cities. They are usually located where a
river meets the sea, and almost always have considerable low area. Cities some-
what upriver from the sea, such as Cairo, Dhaka (Bangladesh), and Jacksonville
(USA), also have serious inundation problems.
Thus sea-level rise seems likely to cause amassive relocationof people and devel-
opment in many coastal urban regions. This suggests the need for a regional,
perhaps 20--30 year plan for sequentially removing people, buildings, roads, and
railroads from low areas, and relocating them elsewhere, such as around certain
satellite cities (Chapter8). If planned well, the relocation of people can produce
large environmental benefits as well. These might include protective coastal wet-
lands and self-building dunes, reestablishing biodiversity and recreation around
long-lost wetlands, and relocating heavy industry away from water-bodies to
designated industry centers with efficient water, power, transport, and waste
disposal.
Unplanned relocations of people in coastal cities may accelerate outward
urbanization and sprawl in the urban region. Alternatively, relocating peo-
ple and development to areas close to the metro-area border could elimi-
nate any existing sprawl there, and be the stimulus for a regional transit-
oriented-development solution to transportation (Chapter2)(Calthorpe1993,
Cervero 1998, Dittmar and Ohland2004). Indeed sea-level rise augurs poorly
for reliance on underground rail or road transportation systems in these cities.