configuration must take account of the details of
the landscape involved (e.g. Fahrig and Merriam
1994). For instance, there may be greater opportu-
nity for dispersal between two distant reserves
linked by a river and its adjacent riparian corridor,
than between two similar but closer reserves sepa-
rated by a mountain barrier of differing habitat
type (Fig. 10.11). For butterflies, differences in land
use as subtle as switches from one woodland type
to another can significantly influence the passage of
butterflies from one favoured habitat patch to
another (Ricketts 2001). An early attempt to place
island theories into realistic landscape contexts was
provided by Harris (1984). Recognizing that there
were limits to the amount of land that would be put
over to reserve use, Harris advocated a series of
reserves placed within the landscape as dictated by
geographical features such as river and mountains,
to encourage population flows between reserves.
Most reserves would remain in forestry manage-
ment. Within such reserves, there should be an
undisturbed core of forest that is never cut, pro-
viding habitat for species requiring undisturbed,
old-growth conditions, around which commercial
operations might continue, following a pattern of
rotational partial felling. This would provide a
mosaic of patches of differing successional stage,
maximizing habitat diversity, while maintaining
income (Fig. 10.12). His strategy aimed to satisfy
the requirements of island theories, patch dynamic
models, and economic realities. The implementa-
tion of such a policy requires concerted action from
a wide variety of agencies and is thus easier to
sketch out than to bring to a realization.
Species that don’t stay put
In the Northern Territory of Australia, as in many
other systems across the globe, mobility and mas-
sive population fluctuations in response to a highly
variable climate are features of the wildlife.
Woinarski et al. (1992) cite as a particular example
the magpie goose (Anseranas semipalmata). They
note that a conventional reserve network consisting
of discrete national parks (such as they have devel-
oped for plants in the region) will not cater for the
need of the magpie geese to relocate in response to
patchiness of rainfall. They identify four possible
strategies for conservation in the Northern Territory:
●The status quo, with improvements to ensure all
vegetation types are included in the network. This
would not solve the problem, as it is not just
vegetation types but the year-to-year variation in
carrying capacity across the region that matters.
●Seeking inclusion of known habitat of important
species into the reserve system. For the magpie
geese, this might mean inclusion of all wetlands.
However, it would be difficult to decide which
species to concentrate on and it would be impracti-
cal to gazette all the land in question because of
competing claims for use.
●Developing very large reserves which span
extensive slices of the environmental gradient, just
as does the present Kakadu National Park, a
20 000 km^2 reserve. However, this would require
vast reserves in the semi-arid and arid region, in
which, at the present time, the largest reserve is of
1325 km^2.
●Supplementing the representative reserve net-
work with measures that protect wildlife habitat on282 ISLAND THEORY AND CONSERVATION
Figure 10.12Harris’s (1984) proposed system for the management
of forest habitat islands on a long-rotation system, such that different
sectors are cut in a programmed sequence, but the core old-growth
patch is left uncut. This recognizes the importance of patch dynamics to
habitat diversity and how such management may serve both economic
and conservation goals. (Redrawn from Harris 1984, Fig. 9.5.).