Whole regions 193Border length of metropolitan area (km)Number of unique/distinctivenatural-systems-related featuresclose (<10km) to metropolitan areaNan•Erz• Edm•Abe•Sam•Ott•0246100 200 300 400(748) Chi+
(707)
(538)Sdt+Bra+Bam+
Buc+ Rom+Bar+Kag•Eas• Can•Teg•Kau+Sto+Sap+Cut•Ula•
Iqu•
Rah•Nai+Phi+Bei*
Seo*
Por•Atl•Mex*
San*
Cai*
Ban Mos*
*Te h*
Ber+Lon*
Figure 7.16Unique/distinctive natural-systems-related features close to a
metropolitan area border relative to the length of the border. The highly diverse
features identified around the 38 metro areas are illustrated by: the main
water-supply reservoir; a major archaeological and tourism site; rare coastal
vegetation site; one of only two wetlands; and only major market-gardening area.
10 0km=62 mi. See Figure 7.2 caption.locations should reduce degradation and maintain the features. Some features
have combined cultural heritage, natural systems, and recreational values.
Border length of built areas in urban regions
[R7] Three-quarters of the urban regions have an average built-area border
‘‘ density” of <5 km length per 100 km^2 (8 mi/100 mi^2 )(Figure7. 17).
High-border-density regions have widespread negative effects of built land on
natural land, and both negative and positive effects of natural land on built
land, as described at the beginning of this chapter. Most urban regions cur-
rently have rather low average border lengths, equivalent to a line less than