Water Stewardship Information Sources

Citation Hebda, R.J., K. Gustavson, K. Golinski and A.M. Calder, 2000. Burns Bog Ecosystem Review Synthesis Report for Burns Bog, Fraser River Delta, South-western British Columbia, Canada. Environmental Assessment Office, Victoria, BC.
Organization Ministry of Environment
URL https://www.burnsbog.org/bog/wp-content/uploads/Burns-Bog-Ecosystem-Review.pdf
Abstract/Description or Keywords Burns Bog is a raised bog ecosystem covering approximately 3,000 ha of the Fraser River delta
between the south arm of the Fraser River and Boundary Bay. On June 1, 1999, the Government
of British Columbia and Delta Fraser Properties Partnership – the owners of 2,200 ha of land
within the Bog - agreed to undertake an ecosystem review to gain a full understanding of what is
needed to preserve the ecological integrity of Burns Bog. The purpose of the Burns Bog
Ecosystem Review (the Review) was to determine the factors crucial to preserving Burns Bog as
a viable ecosystem, such as the hydrology, geology, flora and fauna. The BC Environmental
Assessment Office (EAO) was charged with managing the review process.
The public and stakeholders contributed to developing the nature and scope of the studies
undertaken. Gregory McDade, Q.C., Advisor to the Minister of Environment, Lands and Parks,
facilitated public involvement throughout the review process. The public participated in
reviewing study progress, and in Technical Review Meetings involving local, regional and
international scientific experts. All project materials were accessible through the EAO Project
Registry, at local information outlets, and over the Internet. The key Review findings and
conclusions were developed from the results of technical studies, written submissions, Technical
Review Meetings, and additional information and models developed by the EAO.
The data and models available were generally adequate to lead to conclusions concerning the
requirements for the ecological viability of Burns Bog. However, the data and analyses used in
the Review were limited by the short duration of the study, a lack of previous investigations, and
limited comparative data and examples.
Burns Bog is globally unique on the basis of its chemistry, form, flora and large size. The Bog
exhibits the typical characteristics of a raised bog ecosystem, including a peat mound above the
regional water table, an internal water mound, acidic nutrient-poor water derived directly from
precipitation, a two-layered peat deposit, and widespread peatland communities dominated by
Sphagnum and members of the Heather family.
Today, the Bog is largely isolated from other natural areas by agricultural, residential and
industrial development. Forty percent of the original bog area has been alienated by
development. Many activities, especially peat mining, have disturbed the hydrology and
ecosystems of more than half of the remaining bog area and these disturbances continue to affect
the Bog today. Despite these disturbances, Burns Bog retains important ecological processes
and continues to support distinct biotic communities. The destruction of vegetation and the
upper porous acrotelm layer, combined with the alteration of the hydrological and soil regimes,
have impeded the peat-formation process.
The Bog's hydrology is shaped by the water mound, fluctuating water levels in the acrotelm zone
(top 50 cm), and an extensive system of ditches. The Bog’s ecological viability is directly
dependent on the extent and integrity of the water mound and the peat that encloses it. The
upper porous acrotelm layer is vital to the persistence of the water mound and peat-forming
communities dominated by Sphagnum mosses. Only 29% of the Bog’s original acrotelm and its dynamic water storage zone remain intact. Water from the east side of Highway 91 may play an
important role in sustaining shallow pools that support the main water mound.
The acrotelm plays a vital role in regulating and storing water. As a result of increased rapid
discharge through ditches, the average position of the water table in the acrotelm is about 25 cm
lower than it was in the 1930s. Many ditches reach to the centre of the water mound from all
directions and threaten the future of the Bog. None of the natural drainage channels and little of
the essential lagg zone at the margins remain in the Bog. Further disruption of the water mound
poses high risk to the viability of Burns Bog. The existing area of acrotelm must be maintained
and a fully functional acrotelm must re-develop over the area of the water mound.
A fully functioning lagg is required at the margins of the water mound. The lagg receives
normal discharge from the bog and buffers bog water from adjacent mineral water. The overall
loss of water storage and associated decline in the water table in the past few decades have
contributed to the advance of forested vegetation adjacent to the lagg zone.
The Bog’s water balance suggests a surplus of about 200 mm of precipitation over
evapotranspiration for an average year. Monthly water balance analysis for an average year
shows that there is a moisture deficit from April to September. The relatively low late summer
water table, in the range of 27-39 cm below the surface, may explain why Burns Bog is located
near the climatic limits for raised bogs on the west coast of North America.
Typical bog water occurs in much of the main part of the Bog. It has low pH and relatively low
calcium concentrations. A relatively narrow zone of transitional water, confined to the peat
mass, separates bog water from surrounding mineral-rich waters. Non-bog water with moderate
pH and relatively high mineral concentrations occurs outside the zone of transitional water and
appears to be constrained outside the peat mass. Typical bog ecosystems are associated
primarily with true bog water, and associated, in part, with transitional water.
Originally, the Bog was covered in open heath and Sphagnum vegetation with scattered scrub
pines. Today seven forest, nine shrubby and herbaceous, and six sparsely vegetated ecosystems
occur. The unforested phases of the Lodgepole pine–Sphagnum ecosystem are likely responsible
for most of the peat formation. Herbaceous ecosystems occur widely on abandoned peat
workings and in some natural areas. Lodgepole pine and birch forests encircle the peat-forming
central zone. Other forests, mostly dominated by western redcedar, occur mainly east of
Highway 91. These forests include scattered old-growth trees and are considered to be
regionally rare. Hardhack communities occur in the lagg zone at the Bog margins under
influence of mineral-rich groundwater. The undisturbed peat-forming plant communities of the
southern third and the north-west sector of the Bog are vital to its survival.
Various plant species, including cloudberry, bog-rosemary, crowberry and velvet-leaf blueberry,
occur at the limits of their geographic range and are recognized as genetically and ecologically
important. The Bog also supports at least 12 species of Sphagnum, which constitutes 86% of the
regional Sphagnum flora. The Burns Bog area includes several nationally and provincially listed animals in both the core
central area and at the periphery. The Bog harbours the only known population of the red-listed
Southern Red-backed Vole in the province, as well as the red-listed Pacific Water Shrew. It
provides critical habitat for the regional Greater Sandhill Crane population. Rare dragonflies
and water boatmen occur in the distinct wet habitats of the Bog. Areas at the Bog's periphery are
especially important to rare species and wildlife diversity. The Bog plays an important regional
role in ecological and wildlife diversity by providing habitat for Fraser River estuary waterfowl,
and maintaining the largest extent of bog ecosystems in the Fraser Lowland.
The Bog area is highly sensitive to fire because only about 540 ha of fully functional peatforming
vegetation may survive the next 100 years under the current fire regime. The Bog is
also at risk to a series of drought years that could markedly lower the position of the late summer
water table and threaten typical bog communities. The Bog area must remain large to withstand
these disturbances. Connectivity is limited, but is required to maintain wildlife corridors and the
long-term viability of the Bog.
The conditions for recovery of Burns Bog ecosystems are favourable because there are many
patches of bog vegetation in the disturbed area and a large natural zone surrounding the
disturbed core. Widespread Sphagnum regeneration is occurring in the abandoned peat workings
of the central bog.
To ensure the Bog’s ecological integrity and viability, the entire extant water mound and most of
the lagg zone are required. This requirement includes all of the west and central portions of the
Bog. The area east of Highway 91 and north of 72nd Avenue is required to support high
biodiversity attributes, to provide water to the main part of the Bog west of Highway 91, and to
connect the Bog to upland habitats. The main water mound zone needs to be connected to the
area east of Highway 91 via a broad zone of Sphagnum regeneration and typical bog water.
Water in the shallow ponds within this zone supports the water mound. To sustain the water
mound and peat-forming vegetation, ditches that drain the core of the Bog must be blocked as
soon as possible or the Bog will not survive.
In summary, the area required to preserve Burns Bog as a viable ecosystem includes about 2,450
ha of the remaining bog. Approximately 360 ha, mostly in the south-east and north-east portions
of the study area, have significant values that support the Bog, but that are not required to ensure
ecological viability. Only 14 ha are of low or no value to ecological integrity. Further studies of
hydrology and wildlife are required to define the ecological configuration of specific sites at the
margins of the area required for viability. A program of ongoing monitoring of key indicators of
ecological integrity should be established to ensure the viability of this globally unique
ecosystem.
Information Type report
Regional Watershed Lower Fraser
Sub-watershed if known
Aquifer #
Comments
Project status complete
Contact Name Richard Hebda
Contact Email [email protected]