364
T.J.B. Boyle
was formed to design a management system for spotted owls, and it
recommended the establishment of a network of conservation areas
averaging about 25,000ha and separated by no more than 20 km (Wood,
1991). However, the strategy has come under criticism, and Lande (1988)
has postulated that because of its population genetics foundation, the
strategy is more likely to lead to the extinction of the owl, because it is
unlikely that viable populations will be maintained . Lande argued that
the demographics of the species should provide the basis for the strategy,
because maintenance of demographic processes is much more critical to
the long-term survival of a species than population genetic factors. In this
instance, the spotted owl is fulfilling the role of an "indicator species."
The owl itself is rather less important than the ecosystem it represents.
The marbled murrelet (Brachyramphus marmoratus) appears to perform
a similar function as an indicator of old-growth ecosystem conditons in
the coastal forest of British Columbia (Rodway, Savard, & Regehr,
1991). Although about 70% of the coastal forest is still classified as
old-growth (A. MacKinnon, British Columbia Forest Service, personal
communication), very few of the larger watersheds on Vancouver Island
remain unaffected by logging (Moore, 1990).
Clearcutting obviously causes enormous changes to the ecosystem, with
dramatic consequences to many organisms. For this reason, clearcutting
has been the target of environmental groups and the subject of much
research . The effects of clearcutting on vertebrates is highly variable .
Some species, for example moose, benefit from a mosaic of food and
cover habitats, such as might result from a series of relatively small
clearcuts (Timmermann & McNichol, 1988; Payne , McNichol, Eason et
aI., 1988). Of the common fur-bearing mammals in the boreal forest zone
of Ontario, only the marten (Martes americana) appears to be reliant on
old-growth forest (Thompson , 1988, 1991). Most other fur-bearing species
reach peak densities in early or mid-successional habitats, mainly in response to the buildup of prey species (Thompson , 1988).
Although studies have demonstrated significant decrease in some species
of songbirds following clearcutting , other species are dependent on early
successional stages (Welsh, 1988, 1991). The passerines constitute the
dominant family of birds in the boreal forest, and although some species
are no longer present after clearcutting, others take their place, such that
overall species diversity of all bird species is virtually unchanged (Welsh
& Fillman, 1980). Many species of songbirds are clearly dependent on
specific forest ecosystems, as well as on specific successional stages. A
study of species abundance in northern Ontario in relation to the Forest
Ecosystem Classification system demonstrated quite narrow ecosystem
preferences for many species (Welsh , 1991). Maintaining species diversity
for birds and other fauna therefore requires a continuing supply of forest
ecosystems in various successional stages.
T.J.B. Boyle
was formed to design a management system for spotted owls, and it
recommended the establishment of a network of conservation areas
averaging about 25,000ha and separated by no more than 20 km (Wood,
1991). However, the strategy has come under criticism, and Lande (1988)
has postulated that because of its population genetics foundation, the
strategy is more likely to lead to the extinction of the owl, because it is
unlikely that viable populations will be maintained . Lande argued that
the demographics of the species should provide the basis for the strategy,
because maintenance of demographic processes is much more critical to
the long-term survival of a species than population genetic factors. In this
instance, the spotted owl is fulfilling the role of an "indicator species."
The owl itself is rather less important than the ecosystem it represents.
The marbled murrelet (Brachyramphus marmoratus) appears to perform
a similar function as an indicator of old-growth ecosystem conditons in
the coastal forest of British Columbia (Rodway, Savard, & Regehr,
1991). Although about 70% of the coastal forest is still classified as
old-growth (A. MacKinnon, British Columbia Forest Service, personal
communication), very few of the larger watersheds on Vancouver Island
remain unaffected by logging (Moore, 1990).
Clearcutting obviously causes enormous changes to the ecosystem, with
dramatic consequences to many organisms. For this reason, clearcutting
has been the target of environmental groups and the subject of much
research . The effects of clearcutting on vertebrates is highly variable .
Some species, for example moose, benefit from a mosaic of food and
cover habitats, such as might result from a series of relatively small
clearcuts (Timmermann & McNichol, 1988; Payne , McNichol, Eason et
aI., 1988). Of the common fur-bearing mammals in the boreal forest zone
of Ontario, only the marten (Martes americana) appears to be reliant on
old-growth forest (Thompson , 1988, 1991). Most other fur-bearing species
reach peak densities in early or mid-successional habitats, mainly in response to the buildup of prey species (Thompson , 1988).
Although studies have demonstrated significant decrease in some species
of songbirds following clearcutting , other species are dependent on early
successional stages (Welsh, 1988, 1991). The passerines constitute the
dominant family of birds in the boreal forest, and although some species
are no longer present after clearcutting, others take their place, such that
overall species diversity of all bird species is virtually unchanged (Welsh
& Fillman, 1980). Many species of songbirds are clearly dependent on
specific forest ecosystems, as well as on specific successional stages. A
study of species abundance in northern Ontario in relation to the Forest
Ecosystem Classification system demonstrated quite narrow ecosystem
preferences for many species (Welsh , 1991). Maintaining species diversity
for birds and other fauna therefore requires a continuing supply of forest
ecosystems in various successional stages.