142Nature, food, and water
N1, N2, N3, etc., food section as F1, etc., and water section as W1, etc. Brief
elucidations under each result may: (1) discuss or interpret it; (2) illustrate its
implications ecologically or for society; and (3) identify useful approaches or
solutions for land planning, protection, restoration, and other objectives. Some
solutions are labeled aspriorityand some ashigh priority,relative to the total set
of patterns presented in Chapters6 and7.
Each point in the following graphs represents an urban region. Unlike the
usual scientific graphs that focus on and highlight close correlations between
variables, axes here are chosen to maximize information presentation and to
spread out the data in order to detect variability and contrasting patterns. Thus
most insights and results emerge from examining the four sections or corners
in a graph.Nature in urban regions
Presence of natural patches and landscapes
[N1]Atleast three scales of natural area in urban regions can be readily and
usefully recognized: (1) natural landscapes >100 km^2 ;(2)large natural patches, i.e., the
largest widely distributed ones, which average about 16 km^2 ;and (3) small wooded patches
averaging 0.4 km^2 ,but mostly <0.2 km^2 (<200 ha)(Figures6.3and6.10).
These three size categories emerged qualitatively from extensive perusal of
large (c.70× 10 0cm) images of dozens of urban regions. Geographers, landscape
ecologists, and others have quantitative techniques to determine the frequency
of patch sizes as spatial scale changes (Milne1991a, 1991b,Klopatek and Gardner
1999). Results often show a series of peak patch-size frequencies; the above three
scales seem to correspond to three peaks. The natural-landscape scale proba-
bly mainly reflects the geomorphology of, e.g., hilly areas, mountain ridges,
and major valleys. The large-natural-patch scale may reflect the combination of
geomorphic features, soil types, and human activities on the land. The small-
wooded-patch scale probably reflects farmers’ crop-production practices, as these
patches are overwhelmingly in cropland areas. Natural landscapes are of a size to
protect aquifers, large-home-range species, and so forth (Forman1995). The large
patches are generally sufficient to protect populations of some interior species,
and serve as sources of these species for the surrounding land. The small natural
patches may support isolated rare plants, but are especially useful as stepping
stones for species movement across a cropland landscape.
[N2]Nonatural landscapes are present in 8 %, and no wooded landscapes are present in
16 %,of the regions(Figures6.2and6.3).