Conservation planning 39Connectivity,however, warrants more focus (Forman1995,Bennett 2001, Fahrig
2003,Lindenmayer and Fischer2006,Hiltyet al.2006). Vegetated corridors, such
as water-protection riparian strips, wildlife-movement routes, and walking-trail
routes, can connect the large patches. The next best way to provide connectivity
is with stepping stones, the small sequential patches used by animals to cross a
less-hospitable area. Connectivity and corridors, though much planned and used
as greenways and greenbelts in urban areas, have been more slowly incorporated
in conservation plans. One historical reason was ecologists’ slow recovery after
a1980s controversy about the efficacy of natural corridors, despite an empirical
and conceptual literature overwhelmingly supporting their importance. The sec-
ond more important reason is that large patches are almost universally agreed
tobe the highest conservation priority for land areas, and connectivity, e.g., by
greencorridors, a second priority.
In other words, conservationists do not see a network of green corridors, such
asagreenwaynetwork,astheprimeobjective.Rather,agroup of large natural
patchesor emeralds is the top priority goal. Connecting them with green corri-
dors is the second priority (Saunders and Hobbs 1991 ,Noss and Cooperider1994,
Forman1995,Lindenmayer and Burgman2005).That sequential combination
achieves the big conservation objective provided by anemerald network(Forman
2004a).
The metapopulation concept
One ecological concept, the metapopulation, has recently emerged as
particularly important for land planning and protection. Ametapopulationis a
population subdivided into spatially separate groups, with some movement of
individuals among groups (McCullough1996,Hanskiand Gilpin 1997 ,Linden-
mayer and Burgman2005,Groomet al.2006). For instance, foxes (or deer or kan-
garoos) on four equal-sized patches with periodic dispersal among the patches
represent a metapopulation. In an urban region human activities are constantly
removing large or extensive natural habitat, leaving separate small patches as
fragments of nature. Thus a large fox population in the former large natural area
is converted to four small subpopulations. Over time, small (sub)populations fluc-
tuate more in size, and have more inbreeding and resulting genetic problems,
than do large populations. As a result of these two characteristics, demographic
and genetic, small populations have a greater probability of disappearing or
going locally extinct on a patch. Landscape fragmentation leaves the foxes on
each of the four small patches with a dubious future.
An important alternative to four small patches is a metapopulation dis-
tributed on one large patch and three small ones. In this case, both demographic
fluctuation and genetic inbreeding effects are reduced, because the large patch is