356
T.J.B. Boyle
rare, without doubt many also exist at other sites that have not yet been
reported. It has been estimated that 60 to 70% of British Columbia's
rare and endangered lichens are old-growth dependent (Goward, 1990).
Whereas a 100-year-old coastal western hemlock (Tsuga heterophylla)
forest may contain 8 to 10 species of epiphytic macrolichen species, a 250year-old forest may have more than three times this number and will still
not have reached its maximum complement (Goward, 1991). One reason
for this is that lichens require a high degree of environmental stability,
such as is only found in old-growth forests. Although air pollution, well
known to be a major cause of lichen decline in Europe, may be locally
significant in British Columbia in causing lichen decline in southeastern
Vancouver Island and the southern mainland, cutting of old-growth forest
is likely to pose a far greater threat to lichens, especially those characteristic of the old-growth coastal western hemlock forest (Goward, 1990,
1991).
A proportionately large number of bryophyte species are widely distributed, with only about 23% of the 1221 North American species
being confined to the North American continent, including Mexico
(Schofield, 1980). However, the abundant rainfall and frequent fog of
coastal British Columbia make this region particularly rich in bryophyte
species (Schofield, 1988). The favorable environment, combined with the
survival of many species in glacial refugia in the region, also results in
more endemics and widely disjunct species of bryophytes than elsewhere
in Canada.
In the Coastal forest region, the vascular flora has been most intensively
studied in the Queen Charlotte Island; a detailed account has been
published by Calder and Taylor (1967). Of 593 taxa , 11 are endemic to
the islands, an additional 6 are restricted to the islands and the adjacent
mainland coast of Alaska and northern British Columbia, and 77 more
are found only on the Pacific coast of North America (Calder & Taylor,
1967). The human impact on the flora of Canada and the west coast is
illustrated by considering the number of introduced taxa. For Canada as a
whole, 22% of the species are introduced (Environment Canada, 1991).
The figures are similar for British Columbia (21%, Taylor & MacBryde,
1977) and the Queen Charlotte Islands (20%, Calder & Taylor, 1967).
However, these proportions are more startling when different life habits
are considered. In British Columbia, 47% of annual taxa and 48% of
biennials are introduced, compared with only 14% of perennials (Taylor
& MacBryde , 1977). In the Queen Charlotte Islands , 51 of the 69 annual
taxa and 8 of 13 biennials are introduced, compared with only 11% of the
511 perennial taxa (Calder & Taylor, 1967).
As for many species groups, the total number of species of breeding
birds and mammals in Canada is subject to interpretation of what constitutes a subspecies as opposed to a distinct species. For example, Bunnell
and Williams (1980) report 163 species of mammals in Canada, excluding
T.J.B. Boyle
rare, without doubt many also exist at other sites that have not yet been
reported. It has been estimated that 60 to 70% of British Columbia's
rare and endangered lichens are old-growth dependent (Goward, 1990).
Whereas a 100-year-old coastal western hemlock (Tsuga heterophylla)
forest may contain 8 to 10 species of epiphytic macrolichen species, a 250year-old forest may have more than three times this number and will still
not have reached its maximum complement (Goward, 1991). One reason
for this is that lichens require a high degree of environmental stability,
such as is only found in old-growth forests. Although air pollution, well
known to be a major cause of lichen decline in Europe, may be locally
significant in British Columbia in causing lichen decline in southeastern
Vancouver Island and the southern mainland, cutting of old-growth forest
is likely to pose a far greater threat to lichens, especially those characteristic of the old-growth coastal western hemlock forest (Goward, 1990,
1991).
A proportionately large number of bryophyte species are widely distributed, with only about 23% of the 1221 North American species
being confined to the North American continent, including Mexico
(Schofield, 1980). However, the abundant rainfall and frequent fog of
coastal British Columbia make this region particularly rich in bryophyte
species (Schofield, 1988). The favorable environment, combined with the
survival of many species in glacial refugia in the region, also results in
more endemics and widely disjunct species of bryophytes than elsewhere
in Canada.
In the Coastal forest region, the vascular flora has been most intensively
studied in the Queen Charlotte Island; a detailed account has been
published by Calder and Taylor (1967). Of 593 taxa , 11 are endemic to
the islands, an additional 6 are restricted to the islands and the adjacent
mainland coast of Alaska and northern British Columbia, and 77 more
are found only on the Pacific coast of North America (Calder & Taylor,
1967). The human impact on the flora of Canada and the west coast is
illustrated by considering the number of introduced taxa. For Canada as a
whole, 22% of the species are introduced (Environment Canada, 1991).
The figures are similar for British Columbia (21%, Taylor & MacBryde,
1977) and the Queen Charlotte Islands (20%, Calder & Taylor, 1967).
However, these proportions are more startling when different life habits
are considered. In British Columbia, 47% of annual taxa and 48% of
biennials are introduced, compared with only 14% of perennials (Taylor
& MacBryde , 1977). In the Queen Charlotte Islands , 51 of the 69 annual
taxa and 8 of 13 biennials are introduced, compared with only 11% of the
511 perennial taxa (Calder & Taylor, 1967).
As for many species groups, the total number of species of breeding
birds and mammals in Canada is subject to interpretation of what constitutes a subspecies as opposed to a distinct species. For example, Bunnell
and Williams (1980) report 163 species of mammals in Canada, excluding