connect isolated fragments of original eucalypt woodland in Western Australia.
These corridors result in higher species richness of birds, so that the closer the
corridors to a patch the higher the species number (Fortin and Arnold 1997).
Kangaroos (Macropus robustus) also use corridors to move between remnant patches
of eucalypt woodland in Western Australia (Arnold et al. 1993).
Golden lion tamarins (Leontopithecus r.rosalia) need corridors between patches of
tropical forest habitat, all that remains within a sea of sugarcane fields in Brazil. Rodents,
such as chipmunks and voles, can use fencerows and hedgerows as corridors (La Polla
and Barrett 1993; Bennett et al. 1994). Hill (1995) showed how some poorly dis-
persing insects (butterflies, dung beetles) use corridors but others do not.
The efficacy of corridors needs to be assessed on a case-by-case basis. Thus,
Simberloff and Cox (1987) used the Seychelles islands of the Indian Ocean to make
the point that corridors are not always beneficial. The Seychelles contained 14
endemic land birds when Europeans arrived in 1770. Land clearing, fires, and the
introduction of rats and cats devastated the archipelago over the subsequent two cen-
turies but resulted in the extinction of only two of those species. Losses were limited
partly because no corridors (isthmuses) linked the islands. Introduced predators and
fires were unable to reach all the islands.
The potential advantages and disadvantages of conservation corridors as summar-
ized by Noss (1987) and Saunders and Hobbs (1991) are presented in Box 18.4.Parks are chosen for a number of reasons: great scenery, many species, a cherished
plant association, or a set of interesting landforms. Sometimes the area chooses itself,
being deemed good for little else.
Most national parks established since 1960 (the majority) have been chosen with
some care. They are designed to conserve the plant and animal communities and /or
their associated ecological processes in a particular climatic zone. Having decided upon
the zone the next step is to choose an area within that zone which samples or
epitomizes that zone. The decision is determined first by what land is available for
conversion to a park. It is then determined by whether a piece of available land is
large enough, or can be made large enough by accretion of adjacent areas, to serve
as a national park. Finally a choice is made between the various areas of land that
meet the above criteria.330 Chapter 18
7 5 4 3 2 1 00 200 400 600
Distance to roadside strips (m)Number of species6Fig. 18.1The number
of species of birds in
isolated patches of
eucalypt habitat in
Western Australia is
related to the distance
to roadside strips that
act as corridors or
stepping stones. (Data
from Fortin and Arnold
1997.)
18.5.6Effects of
initial conditions