19 4Built systems, built areas, and whole regions
Abundance or “density” of built-area borders in urban region(average border length in km per 100 km2 )
LondonBerlin+Rome+Bucharest+Stockholm+Barcelona+NantesChicago+San Diego/Tijuana+Philadelphia+Ottawa•EdmontonPortlandAtlantaMexico CitySantiagoBrasilia+TegucigalpaIquitos- Cairo
*
Nairobi+Bamako+East LondonAbecheBeijing*
MoscowSeoul*
Te h r a n*
Sapporo+UlaanbaatarErzurumKagoshimaBangkokKuala Lumpur+CuttackSamarindaCanberraRahimyar KhanEurope North
AmericaLatin
AmericaAfrica West-East
AsiaSouth Asia-
AustraliaAverageGeographic area, with cities from large to small population3
6
9
12
15
0
Figure 7.17Abundance or ‘‘density” of built-area borders in urban region
relative to geography and city size. Abundance or density equals total border
length [metro area + inner satellite cities + outer satellite cities + towns]×100,
divided by area of urban region. 1 km/km^2 =1.6 mi/mi^2. See Figure 7.2 caption.5m(16 ft) long in a football field. However the Chicago and Philadelphia regions,
with >12 km/100 km^2 border density, are outliers (Color Figures 13 and ). Much
surrounding greenspace in these regions is doubtless degraded.
[R8]Overall,the metropolitan area contributes >40 % and towns <40 % to total border
length in a region; satellite cities contribute the least and have the least-variable total-
border-length from region to region(Figure7. 18).