Here are three examples from the
fern, orchid and iris clans:
The Southern Maidenhair Fern
(Adiantum capillus-veneris) occurs in just one location in
Canada: at Fairmont Hot Springs. It is Red-listed
in British Columbia (provincial rank S1, global rank G5), and is
on the COSEWIC Endangered list. Although this population has been
severely depleted by development of the site, the potential exists
for it to be re-established, not only at this site, but at other
hot springs in the region.
The Gaint Heleborine (Epipactic
gigantea), an orchid, formerly occurred in 15 sites in British
Columbia, "...half of which may may no longer exist because
of hydro dam flooding and other developments." (Burnett et
al., 1989). Formerly classed by COSEWIC as Threatened, it was downgraded
in 1998 to Vulnerable. It is Red-listed
in British Columbia, provincial CDC rank S2 and global rank G4.
As an orchid, it is a CITES Appendix II species. Now absent from
Radium Hot Springs, where it formerly occurred, it persists at a
single site at Fairmont Hot Springs and at several locations around
Kootenay Lake and elsewhere in British Columbia.
Western Blue-flag Iris (Iris
missouriensis) favours the same kind of wet meadow and streamside
habitat that is also favoured by people and livestock, and valley
bottoms now flooded for hydroelectric development. It is on the
COSEWIC Threatened list, but is unlisted in British Columbia.
Conservation Issues
The conservation issues for rare
and endangered plants can be placed in three categories: land use
(mainly of range lands), disturbance to specialized habitats, and
introduction and spread of exotic species.
Range use raises conservation issues
for plants by (a) alienating plant habitats by urban and agricultural
developments and (b causing disturbance over a wide area through
livestock (mainly cattle) grazing. The distribution map (above)
shows that many of the region's rarest and most endangered plants
occur in the major valleys, especially along rivers and creeks in
riparian habitats. These are the areas most heavily used for crops,
wintering livestock and settlement. Not surprisingly, rare and endangered
animals follow a similar distribution. There is, however, considerable
cause for optimism. Even within heavily used environments like cities
and farms, there are many opportunities to protect semi-natural
habitats. Native plants, even rare ones, can survive in semi-natural
stream set-backs, urban parklands and "green" corridors.
Agricultural communities are also finding that leaving native vegetation
along fencerows (or by allowing previously plowed strips of land
to recolonize with native vegetation) takes little land out of production,
and provides "integrated pest management" dividends. These
include rodent control (by hawks and mammalian predators), crop
pollination by native insects, and natural controls on harmful insect
pests by insect predators and parasites and avian predators, all
of which thrive (or at least survive) along fencerows and vegetated
stream edges. These semi-natural habitats not only give plants a
place to live, but provide opportunities for the slow-dispersers
(for example, those that spread seeds slowly over short distances
- which includes nearly all threatened plants) to disperse into
new habitats and maintain gene flow between populations.
Livestock grazing is more problematic.
Livestock trample the ground, disrupting the natural crust that
forms of lichens and organic material in the microlayer of arid
region soils (see Pitt and Hooper, 1994). Disturbing this crust
allows more rapid evaporation and consequent more severe soil moisture
deficits. Livestock also preferentially graze certain plants while
leaving others, and their feces scatter seeds of alien plant species,
many of which compete with native plants (particularly on disturbed
soils). Although public grazing lands are better managed now than
in the past (Pitt and Hooper, 1994) livestock are difficult to manage
for plant conservation purposes on public lands, and nearly impossible
on private lands. Moreover, even the few protected areas that have
been established in grassland and grassy-understory forest types
are hardly effective for plant conservation because of the expense
(not to mention the controversy that would ensue) of fencing them
to exclude livestock. Even so, livestock exclosures and low stocking
densities are really the only effective means of conserving rare
plants that occur over a wide area.
As noted in the Grassland
Ecosystem section, exclusion of fire from fire-maintained
ecosystems (e.g., the Ponderosa Pine
biogeoclimatic zone) causes wholesale changes in plant
communities through competition with other plants.
Rare plants of specialized habitats
are potentially easier to save. In the Columbia Basin, hot springs
are home to a considerable variety of rare and endangered plants,
and these small sites can be controlled, with some awareness and
commitment. Unfortunately, the existence and value of rare plants
has not always been realized in time to prevent serious damage.
References and further
reading
- Burnett, J.A., C.T. Dauphiné, S.H. McCrindle
and T. Mosquin, 1989. On the Brink: Endangered Species in
Canada. Environment Canada.
Douglas, G.W., G.B.Straley, and D. Meidinger, 1998. Rare
Native Vascular Plants of British Columbia, Ministry of Environment,
Lands and Parks, Victoria, B.C.
Beardmore, Roger M., 1999. The Columbia Basin: Endangered
Species and Spaces. By Future Legacy Consulting Group for Royal
British Columbia Museum and Columbia Basin.
Pitt, M. and T.D. Hooper, 1994. Threats to biodiversity
of grassland ecosystems in British Columbia. In L.E.
Harding and E. McCullum (ed.s), Biodiversity in British Columbia:
Our Changing Environment. Environment Canada.
Species At Risk Topics
