This Earthcache will help you learn about the Camosun Bog area
of Pacific Spirit Regional Park. Please stay on the boardwalk and
note that this is an on-leash dog area.
Earthcache Logging Requirements
To log this cache you must take a photograph of your
caching crew in the Camosun Bog area and post it in your cache log.
In addition, please email me with the answers to the following
questions.
- If you start off facing the information boards in the centre of
the bog and turn around, what is the total length of boardwalk (in
metres) that encloses the bog area that you are looking at?
- In what condition was Vancouver 12,000 years ago?
- What happened 3,000 years ago to turn this area into a
bog?
- What was done in 1991 in an attempt to restore the bog?
- Name three plants native to the bog ecosystem.
Formation of Camosun Bog
The bog’s history can be traced back many thousands of
years. The Cordilleran ice sheet once extended to the southern end
of Puget Sound, covering the area now known as Vancouver with a
kilometre-thick layer of glacial ice. 12,500 years ago, as the ice
retreated, it left behind a scarred landscape, thick with glacial
till. An enormous piece of ice remained in the area which is now
Camosun Bog, the weight of which produced a depression in the rock.
As the ice melted slowly, a lake formed. Gradually, vegetation took
hold in the surrounding area, initially characterized by lichens,
followed by mosses, saxifrage and dwarf shrubs, and eventually
becoming dominated by the Douglas fir, alder, hemlock and cedar
that colonize Pacific Spirit Park today.
Many of the lakes and ponds formed after glacial retreat were
destined to become filled with sediment and disappear beneath the
spreading forest, but a different outcome was in store for the lake
at Point Grey. At the edges of the lake, plants which were adapted
to wet littoral conditions, including sedges and cattails, began to
grow. Organic material, and sediment brought by streams feeding the
lake, accumulated on the bed and at the edges of the lake. This
build-up of material resulted in a shift to marshy conditions which
gradually encroached on the lake proper, a process known as
hydrosere succession. As un-decomposed dead vegetable matter
accumulated around the roots and stems of rushes and sedges, the
marsh gave way to swamp, and the lake contracted further.
Swamp-loving plants, such as swamp laurel and Labrador tea,
flourished in the moist environment at the edge of the lake. This
increase in growth was inevitably accompanied by an increase in
decomposition, and the consumption of oxygen in this process
resulted in anaerobic soil conditions. In addition, a build-up in
organic matter restricted the flow of water into the area,
resulting in a decrease in nutrient supply.
Anaerobic and nutrient poor soils are unfavourable to the growth
of most plants, but create conditions ideal for the invasion of
Sphagnum moss. Once established, Sphagnum moss is able to thrive
and spread, bringing about the development of a Sphagnum peat bed
under the bog surface. The acidic, nutrient-poor, heat-insulating
and slowly permeable characteristics of this peat further inhibit
the growth of other plant life, and the lack of competition for
light and water further facilitates the growth of Sphagnum and the
expansion of the peat bed. Sphagnum not only tolerates a lack of
nutrients, a high water table, and acidic conditions, it helps to
sustain these conditions by further acidifying the water in which
sphagnum grows.
The decline of Camosun Bog
Camosun Bog has faced many threats since the Vancouver area was
first populated by people of European origin in the mid-nineteenth
century.
- Although logging was largely restricted to the forests
surrounding the bog which were rich in the more valuable species
Douglas fir and cedar, removal of large trees from the bog
catchment affected the nutrient balance, destabilizing the bog
ecosystem. Through their activities, loggers also left the kindling
for fires that would sweep through the area, destroying all
vegetation.
- In 1886, the City of Vancouver was incorporated, and land
development became a new threat to the bog. By 1912, streetcars ran
within a kilometre of the bog and urban development had extended
into its northern and eastern fringes.
- In 1919 fire engulfed the bog again. Pollen and tree-ring
studies confirm that most of the taller tree species (shore pines,
swamp laurel, Labrador tea and alder) were burned, and the surface
growth, including Sphagnum moss, was damaged.
- In 1929, drainage was put in place to draw water away from the
bog, as local disdain for the bog grew. Local residents saw the bog
as a dangerous and unsightly place and a breeding ground for
mosquitoes. Drier conditions allowed hemlock to thrive, which led
to a rapid change in the bog as the increased transpiration,
deposition of litter and creation of shade further inhibited the
growth of bog plants.
- Following the stock market crash of 1929, permits were granted
to local residents to cut firewood from the Endowment Lands. In the
1940s, cutting was restricted to the vicinity of the bog, as this
held "little attraction for riders and posed the least amount of
fire hazard".
- In 1952, three local children who lived near the bog contracted
polio, and parents and local residents rose in alarm and outrage,
pointing the finger at the “swamp”, contaminated by a
septic tank. The decision was made to link up local houses to the
sewer network, and to drain the “polio swamp”.
- In the 1950s, the growing local population demanded
recreational facilities, and the bog’s northern edge and
southeastern corner were converted into a playing field and a
baseball diamond respectively. Construction of a BC Hydro
substation and power lines in 1960 further encroached upon the
bog.
- In the 1970s, the University of British Columbia (UBC) used the
bog as a landfill site to dispose of excavated material created
during the expansion of the university. As a consequence, Camosun
Bog was on the verge of disappearance at the end of the 1970s. The
water table dropped, and the decreasingly acidic soil favoured the
establishment of non-bog species, including hemlock.
Restoration of Camosun Bog
Attitudes towards the environment changed in the 1970s and the
battle to save Camosun Bog began. Members of the University
community challenged the University administration's decision to
turn the bog into a landfill, and eventually managed to have the
dumping stopped. In December 1988, Pacific Spirit Park was
established, under the authority of the GVRD. Shortly thereafter,
the Camosun Bog subcommittee, set up by UBC, put forward a Proposal
for the Restoration of Camosun Bog. In the winter of 1990-1991,
volunteers from the Vancouver Natural History Society began active
efforts to restore the bog to its natural state. After many
thousands of hours of work, the bog has been partly restored to its
former state. Major accomplishments include:
- removal of invading hemlock trees, in order to reduce loss of
water in the summer by transpiration from the trees, to remove a
source of nutrients coming into the bog from the leaf litter, and
to open up the bog surface to sunlight. However, removal of hemlock
trees allowed birch trees to thrive, necessitating another arduous
tree removal project, which is now complete. The battle to keep out
other invasive species, including blackberry, hardhack and
salmonberry is ongoing;
- in order to effectively raise the summer water table, the
ground level itself was lowered, exposing the peat surface.
Sphagnum moss was transplanted onto this surface, and took hold in
the higher areas of the bog. The success of this project became
apparent when other bog plants, such as sundew and Labrador tea,
spontaneously appeared in the bog;
- an excavator was used to clear a large area of non-bog
vegetation. The peat surface was then landscaped by hand, before
the area was planted with sphagnum and bog plants like Labrador tea
and bog laurel; and
- a boardwalk around the bog has been recently completed,
allowing visitors to the bog to survey the area, without causing
damage to the fragile bog surface. In future, signage will be
installed to educate the public about the key natural features of
the bog.
For more information on Camosun Bog and to find out about
volunteer opportunities, please visit Camosun
Bog Restoration Group
References
Wynn, Graeme and Hermansen, S., 2005. Reflections on the Nature
of an Urban Bog. Urban History Review. 34.1
Parks and Nature Places Around Vancouver, edited by Alison
Parkinson, published by Harbour Publishing.
Camosun Bog Restoration Project.
www.naturalhistory.bc.ca/CamosunBog