Patchsizes, edges, and habitats 225France (2003), Lindenmayer and Burgman (2005), Groomet al.(2006), Wiens and
Moss (2005), Perlman and Milder (2005), Fischeret al.(2006), and Lindenmayer
and Fischer (2006). Chapter4 elaborates on some of the principles, even suggest-
ing others.
These principles are listed in four groupings: (1) patch size and edge; (2) natu-
ralhabitats for conservation; (3) species-focused conservation; and (4) wetlands.
Patchsize and edge
(A) Large-patch benefits. Large patches of natural vegetation are the only struc-
tures in a landscape that protect aquifers and interconnected stream
networks, sustain viable populations of many interior species, provide
core habitat and escape cover for most large-home-range vertebrates,
and support near-natural disturbance regimes and plants dependent on
them.
(B) Edge width of a natural community. Edge width, which largely results from
penetration of wind, solar energy, and human influence into a natural
community, is the distance with significant effects on sensitive ecologi-
cal variables, such as desiccation, seedling mortality, herbaceous species,
and upper soil layer conditions.
(C) Edge and interior species.Amore convoluted natural-vegetation patch, or
one that has been subdivided into two smaller patches, will have a
higher proportion of edge habitat with slightly more generalist edge
species, but will contain significantly fewer and smaller populations of
interior species, including those of conservation importance.
(D) Small-patch benefits.Small natural-vegetation patches scattered across a
less-suitable matrix act as stepping stones enhancing the movement of
some species, provide some protection for widely scattered uncommon
species, and, if near a large patch, may enhance species richness and
movement associated with the large patch.
(E) Populations in small patches.Small patches, especially if isolated, tend to
have smaller populations which fluctuate more over time, more inbreed-
ing and resulting genetic deficiencies, and therefore a greater chance
of local extinction or disappearance.
(F) Human impacts and protected areas.Closing spur roads and roads that
bisect the interior of a large protected patch, and concentrating recre-
ational opportunities and facilities for people in the edge portion of a
protected area are effective ways to protect resources, especially in the
interior of a large protected patch.
(G) Boundary characteristics.Boundaries or edges of a habitat, including their
three-dimensional structure, distinctive microclimate and soil, and high