146Nature, food, and water
Phi+Por•Sto+Sap+ Mex*
Bra+
Ber+Area of metropolitan area (km^2 )Elongation of metro area between nearby similar landscapes (length to width ratio)
0 500 1000 1500 2000 25001.01.21.41.61.82.0Figure 6.4Elongation of metropolitan area between similar landscapes relative to
size of metropolitan area. Metro-area sizeis measured with a planimeter on large
1:200 000 satellite images. Landscapes are >100 km^2 and compact in shape; all are
wooded except Philadelphia which is agricultural. Long axis of metro-area separates
thelandscapes. 100 km^2 = 38.6 mi^2. See Chapter5 fornatural vegetation types, and
Figure 6.2 caption for city information.disease or pest. Rather than a group of patches, the emerald network functions
as a system of patches and corridors for both biodiversity and recreation. Protect-
ing the connections, the most vulnerable places, is especially important. A viable
emerald network is a key long-termhigh priorityobjective for many regions.
[N7]In a sixth of the regions, an elongated metropolitan area lies between two nearby
similar, usually wooded, landscapes(Figure6.4).
In these cases the metro area doubtless serves as a significant barrier to
regional species movement between the nearby landscapes (Pauleitet al.2005). In
one case (Philadelphia), the metro area separates cropland landscapes containing
scattered small woods, and across which many forest birds may readily move
(Knaapenet al.1992,Forman1995). The only really long and narrow metro area
is Iquitos, which, however, is nearly surrounded by rainforest.
Adual approach to overcoming the barrier effect of elongated metro areas
may be best. Strengthening or creating rows of parks or linear greenspaces
across the metro area would help reconnect the landscapes on opposite sides.
Establishing a large elongated greenspace at each end of the metro area, and