Dispersal, migration and management - Ecological Applications: Toward a Sustainable World - page 97

4.5 Species mobility
and management of
production
landscapes

Human industry and resource exploitation inevitably have consequences for natural
ecosystems. Given the undeniable need to exploit forest for timber (Sections 4.5.1,
4.5.2), to generate energy (Section 4.5.3), and to grow agricultural crops (Section
4.5.4), the aim of resource managers is twofold. First, to designate areas where this
might be done with minimal consequences for the natural world and, second, to
ensure that production landscapes are managed in a sustainable manner. I will come
to the question of the zoning of production and conservation across landscapes and
waterscapes in Chapter 10, because this is the domain of community and ecosystem
ecology. Here, I will confront the question of sustaining individual species in
exploited landscapes, with continuing emphasis on the relevance of species mobility
for conservation.

4.5.1 Squirrels -
axeman spare that
tree

The fl ying squirrel Pteromys volans in Finland has declined dramatically because of
habitat loss, habitat fragmentation and reduced habitat connectivity caused by
intensive forestry. This nocturnal squirrel favors spruce-dominated forest ( Picea
abies ) with a marked component of deciduous trees such as aspen ( Populus tremula ),
birch ( Betula spp.) and alder ( Alnus spp.). Aspens are probably the most important
of these, providing both food for the squirrels and shelter in the form of woodpecker
cavities. Areas of natural forest, critical to the squirrels, are now separated by clear-
cut and regenerating areas.
The core breeding habitat of a fl ying squirrel only occupies a few hectares, but
individuals, particularly males, move to and from this core for temporary stays in
a much larger 'dispersal' area (1-3 km 2 ), and juveniles permanently disperse away
from their parents within this range. Reunanen et al. (2000) compared the landscape
structure around known fl ying squirrel home ranges (63 sites) with randomly
chosen areas (96 sites) to determine the forest patterns that the squirrels need. They
fi rst established that the landscape could be divided into optimal breeding habitat
(mixed spruce-deciduous forests), dispersal habitat (pine ( Pinus sylvestris ) and
young forests) and unsuitable habitat (young sapling stands and open habitats).
Figure 4.10 shows the spatial arrangement of breeding and dispersal habitat for a
typical fl ying squirrel site and a random forest site. Overall, fl ying squirrel land-
scapes contain three times more suitable breeding habitat and 23% more dispersal
habitat than random landscapes. But, most notably, squirrel dispersal habitat is
much better connected (fewer fragments per unit area) than random landscapes.
Reunanen and his colleagues recommend that forest managers should restore and
maintain a deciduous mix of trees for optimal breeding habitat. And of particular
signifi cance in the context of dispersal behavior, they need to ensure good physical
connectivity between optimal breeding and dispersal habitat.

4.5.2 Bats - axeman
cut that track

In stark contrast to the fl ying squirrels, bats can sometimes be favored by certain
forestry practices! Bats vary in wing shape and echolocation calls in a way that
infl uences their operation in different habitats. For example, those with long thin
wings, which make them less maneuverable, or with calls of relatively low fre-
quency, fi nd it diffi cult to negotiate cluttered habitats. As vegetation regenerates after
logging, stem density and vegetation clutter (structural complexity) increase. With
this in mind, Law and Chidel (2002) investigated the effects of logging (15 years
later) in a Eucalyptus forest in New South Wales, Australia. Prior to logging, the tall,
wet forest was dominated by two tree species, Sydney blue gum ( Eucalyptus saligna )